/*
* Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "jvm.h"
#include "aot/aotLoader.hpp"
#include "classfile/classLoader.hpp"
#include "classfile/javaClasses.hpp"
#include "classfile/moduleEntry.hpp"
#include "classfile/systemDictionary.hpp"
#include "classfile/vmSymbols.hpp"
#include "code/codeCache.hpp"
#include "code/scopeDesc.hpp"
#include "compiler/compileBroker.hpp"
#include "compiler/compileTask.hpp"
#include "gc/shared/barrierSet.hpp"
#include "gc/shared/gcId.hpp"
#include "gc/shared/gcLocker.inline.hpp"
#include "gc/shared/workgroup.hpp"
#include "interpreter/interpreter.hpp"
#include "interpreter/linkResolver.hpp"
#include "interpreter/oopMapCache.hpp"
#include "jfr/jfrEvents.hpp"
#include "jvmtifiles/jvmtiEnv.hpp"
#include "logging/log.hpp"
#include "logging/logConfiguration.hpp"
#include "logging/logStream.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/metaspaceShared.hpp"
#include "memory/oopFactory.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "oops/access.inline.hpp"
#include "oops/instanceKlass.hpp"
#include "oops/objArrayOop.hpp"
#include "oops/oop.inline.hpp"
#include "oops/symbol.hpp"
#include "oops/typeArrayOop.inline.hpp"
#include "oops/verifyOopClosure.hpp"
#include "prims/jvm_misc.hpp"
#include "prims/jvmtiExport.hpp"
#include "prims/jvmtiThreadState.hpp"
#include "runtime/arguments.hpp"
#include "runtime/atomic.hpp"
#include "runtime/biasedLocking.hpp"
#include "runtime/fieldDescriptor.inline.hpp"
#include "runtime/flags/jvmFlagConstraintList.hpp"
#include "runtime/flags/jvmFlagRangeList.hpp"
#include "runtime/flags/jvmFlagWriteableList.hpp"
#include "runtime/deoptimization.hpp"
#include "runtime/frame.inline.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/handshake.hpp"
#include "runtime/init.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "runtime/java.hpp"
#include "runtime/javaCalls.hpp"
#include "runtime/jniHandles.inline.hpp"
#include "runtime/jniPeriodicChecker.hpp"
#include "runtime/memprofiler.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/objectMonitor.hpp"
#include "runtime/orderAccess.hpp"
#include "runtime/osThread.hpp"
#include "runtime/prefetch.inline.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/safepointMechanism.inline.hpp"
#include "runtime/safepointVerifiers.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/statSampler.hpp"
#include "runtime/stubRoutines.hpp"
#include "runtime/sweeper.hpp"
#include "runtime/task.hpp"
#include "runtime/thread.inline.hpp"
#include "runtime/threadCritical.hpp"
#include "runtime/threadSMR.inline.hpp"
#include "runtime/threadStatisticalInfo.hpp"
#include "runtime/timer.hpp"
#include "runtime/timerTrace.hpp"
#include "runtime/vframe.inline.hpp"
#include "runtime/vframeArray.hpp"
#include "runtime/vframe_hp.hpp"
#include "runtime/vmThread.hpp"
#include "runtime/vmOperations.hpp"
#include "runtime/vm_version.hpp"
#include "services/attachListener.hpp"
#include "services/management.hpp"
#include "services/memTracker.hpp"
#include "services/threadService.hpp"
#include "utilities/align.hpp"
#include "utilities/copy.hpp"
#include "utilities/defaultStream.hpp"
#include "utilities/dtrace.hpp"
#include "utilities/events.hpp"
#include "utilities/macros.hpp"
#include "utilities/preserveException.hpp"
#include "utilities/singleWriterSynchronizer.hpp"
#include "utilities/vmError.hpp"
#if INCLUDE_JVMCI
#include "jvmci/jvmci.hpp"
#include "jvmci/jvmciEnv.hpp"
#endif
#ifdef COMPILER1
#include "c1/c1_Compiler.hpp"
#endif
#ifdef COMPILER2
#include "opto/c2compiler.hpp"
#include "opto/idealGraphPrinter.hpp"
#endif
#if INCLUDE_RTM_OPT
#include "runtime/rtmLocking.hpp"
#endif
#if INCLUDE_JFR
#include "jfr/jfr.hpp"
#endif
// Initialization after module runtime initialization
void universe_post_module_init(); // must happen after call_initPhase2
#ifdef DTRACE_ENABLED
// Only bother with this argument setup if dtrace is available
#define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
#define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
#define DTRACE_THREAD_PROBE(probe, javathread) \
{ \
ResourceMark rm(this); \
int len = 0; \
const char* name = (javathread)->get_thread_name(); \
len = strlen(name); \
HOTSPOT_THREAD_PROBE_##probe(/* probe = start, stop */ \
(char *) name, len, \
java_lang_Thread::thread_id((javathread)->threadObj()), \
(uintptr_t) (javathread)->osthread()->thread_id(), \
java_lang_Thread::is_daemon((javathread)->threadObj())); \
}
#else // ndef DTRACE_ENABLED
#define DTRACE_THREAD_PROBE(probe, javathread)
#endif // ndef DTRACE_ENABLED
#ifndef USE_LIBRARY_BASED_TLS_ONLY
// Current thread is maintained as a thread-local variable
THREAD_LOCAL Thread* Thread::_thr_current = NULL;
#endif
// ======= Thread ========
// Support for forcing alignment of thread objects for biased locking
void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
if (UseBiasedLocking) {
const size_t alignment = markWord::biased_lock_alignment;
size_t aligned_size = size + (alignment - sizeof(intptr_t));
void* real_malloc_addr = throw_excpt? AllocateHeap(aligned_size, flags, CURRENT_PC)
: AllocateHeap(aligned_size, flags, CURRENT_PC,
AllocFailStrategy::RETURN_NULL);
void* aligned_addr = align_up(real_malloc_addr, alignment);
assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
"JavaThread alignment code overflowed allocated storage");
if (aligned_addr != real_malloc_addr) {
log_info(biasedlocking)("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
p2i(real_malloc_addr),
p2i(aligned_addr));
}
((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
return aligned_addr;
} else {
return throw_excpt? AllocateHeap(size, flags, CURRENT_PC)
: AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
}
}
void Thread::operator delete(void* p) {
if (UseBiasedLocking) {
FreeHeap(((Thread*) p)->_real_malloc_address);
} else {
FreeHeap(p);
}
}
void JavaThread::smr_delete() {
if (_on_thread_list) {
ThreadsSMRSupport::smr_delete(this);
} else {
delete this;
}
}
// Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
// JavaThread
DEBUG_ONLY(Thread* Thread::_starting_thread = NULL;)
Thread::Thread() {
DEBUG_ONLY(_run_state = PRE_CALL_RUN;)
// stack and get_thread
set_stack_base(NULL);
set_stack_size(0);
set_lgrp_id(-1);
DEBUG_ONLY(clear_suspendible_thread();)
// allocated data structures
set_osthread(NULL);
set_resource_area(new (mtThread)ResourceArea());
DEBUG_ONLY(_current_resource_mark = NULL;)
set_handle_area(new (mtThread) HandleArea(NULL));
set_metadata_handles(new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(30, true));
set_active_handles(NULL);
set_free_handle_block(NULL);
set_last_handle_mark(NULL);
DEBUG_ONLY(_missed_ic_stub_refill_verifier = NULL);
// Initial value of zero ==> never claimed.
_threads_do_token = 0;
_threads_hazard_ptr = NULL;
_threads_list_ptr = NULL;
_nested_threads_hazard_ptr_cnt = 0;
_rcu_counter = 0;
// the handle mark links itself to last_handle_mark
new HandleMark(this);
// plain initialization
debug_only(_owned_locks = NULL;)
NOT_PRODUCT(_no_safepoint_count = 0;)
NOT_PRODUCT(_skip_gcalot = false;)
_jvmti_env_iteration_count = 0;
set_allocated_bytes(0);
_vm_operation_started_count = 0;
_vm_operation_completed_count = 0;
_current_pending_monitor = NULL;
_current_pending_monitor_is_from_java = true;
_current_waiting_monitor = NULL;
_current_pending_raw_monitor = NULL;
_num_nested_signal = 0;
om_free_list = NULL;
om_free_count = 0;
om_free_provision = 32;
om_in_use_list = NULL;
om_in_use_count = 0;
#ifdef ASSERT
_visited_for_critical_count = false;
#endif
_SR_lock = new Monitor(Mutex::suspend_resume, "SR_lock", true,
Monitor::_safepoint_check_sometimes);
_suspend_flags = 0;
// thread-specific hashCode stream generator state - Marsaglia shift-xor form
_hashStateX = os::random();
_hashStateY = 842502087;
_hashStateZ = 0x8767; // (int)(3579807591LL & 0xffff) ;
_hashStateW = 273326509;
_OnTrap = 0;
_Stalled = 0;
_TypeTag = 0x2BAD;
// Many of the following fields are effectively final - immutable
// Note that nascent threads can't use the Native Monitor-Mutex
// construct until the _MutexEvent is initialized ...
// CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
// we might instead use a stack of ParkEvents that we could provision on-demand.
// The stack would act as a cache to avoid calls to ParkEvent::Allocate()
// and ::Release()
_ParkEvent = ParkEvent::Allocate(this);
_MuxEvent = ParkEvent::Allocate(this);
#ifdef CHECK_UNHANDLED_OOPS
if (CheckUnhandledOops) {
_unhandled_oops = new UnhandledOops(this);
}
#endif // CHECK_UNHANDLED_OOPS
#ifdef ASSERT
if (UseBiasedLocking) {
assert(is_aligned(this, markWord::biased_lock_alignment), "forced alignment of thread object failed");
assert(this == _real_malloc_address ||
this == align_up(_real_malloc_address, markWord::biased_lock_alignment),
"bug in forced alignment of thread objects");
}
#endif // ASSERT
// Notify the barrier set that a thread is being created. The initial
// thread is created before the barrier set is available. The call to
// BarrierSet::on_thread_create() for this thread is therefore deferred
// to BarrierSet::set_barrier_set().
BarrierSet* const barrier_set = BarrierSet::barrier_set();
if (barrier_set != NULL) {
barrier_set->on_thread_create(this);
} else {
// Only the main thread should be created before the barrier set
// and that happens just before Thread::current is set. No other thread
// can attach as the VM is not created yet, so they can't execute this code.
// If the main thread creates other threads before the barrier set that is an error.
assert(Thread::current_or_null() == NULL, "creating thread before barrier set");
}
}
void Thread::initialize_thread_current() {
#ifndef USE_LIBRARY_BASED_TLS_ONLY
assert(_thr_current == NULL, "Thread::current already initialized");
_thr_current = this;
#endif
assert(ThreadLocalStorage::thread() == NULL, "ThreadLocalStorage::thread already initialized");
ThreadLocalStorage::set_thread(this);
assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
}
void Thread::clear_thread_current() {
assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
#ifndef USE_LIBRARY_BASED_TLS_ONLY
_thr_current = NULL;
#endif
ThreadLocalStorage::set_thread(NULL);
}
void Thread::record_stack_base_and_size() {
// Note: at this point, Thread object is not yet initialized. Do not rely on
// any members being initialized. Do not rely on Thread::current() being set.
// If possible, refrain from doing anything which may crash or assert since
// quite probably those crash dumps will be useless.
set_stack_base(os::current_stack_base());
set_stack_size(os::current_stack_size());
#ifdef SOLARIS
if (os::is_primordial_thread()) {
os::Solaris::correct_stack_boundaries_for_primordial_thread(this);
}
#endif
// Set stack limits after thread is initialized.
if (is_Java_thread()) {
((JavaThread*) this)->set_stack_overflow_limit();
((JavaThread*) this)->set_reserved_stack_activation(stack_base());
}
}
#if INCLUDE_NMT
void Thread::register_thread_stack_with_NMT() {
MemTracker::record_thread_stack(stack_end(), stack_size());
}
#endif // INCLUDE_NMT
void Thread::call_run() {
DEBUG_ONLY(_run_state = CALL_RUN;)
// At this point, Thread object should be fully initialized and
// Thread::current() should be set.
assert(Thread::current_or_null() != NULL, "current thread is unset");
assert(Thread::current_or_null() == this, "current thread is wrong");
// Perform common initialization actions
register_thread_stack_with_NMT();
JFR_ONLY(Jfr::on_thread_start(this);)
log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
os::current_thread_id(), p2i(stack_base() - stack_size()),
p2i(stack_base()), stack_size()/1024);
// Perform <ChildClass> initialization actions
DEBUG_ONLY(_run_state = PRE_RUN;)
this->pre_run();
// Invoke <ChildClass>::run()
DEBUG_ONLY(_run_state = RUN;)
this->run();
// Returned from <ChildClass>::run(). Thread finished.
// Perform common tear-down actions
assert(Thread::current_or_null() != NULL, "current thread is unset");
assert(Thread::current_or_null() == this, "current thread is wrong");
// Perform <ChildClass> tear-down actions
DEBUG_ONLY(_run_state = POST_RUN;)
this->post_run();
// Note: at this point the thread object may already have deleted itself,
// so from here on do not dereference *this*. Not all thread types currently
// delete themselves when they terminate. But no thread should ever be deleted
// asynchronously with respect to its termination - that is what _run_state can
// be used to check.
assert(Thread::current_or_null() == NULL, "current thread still present");
}
Thread::~Thread() {
// Attached threads will remain in PRE_CALL_RUN, as will threads that don't actually
// get started due to errors etc. Any active thread should at least reach post_run
// before it is deleted (usually in post_run()).
assert(_run_state == PRE_CALL_RUN ||
_run_state == POST_RUN, "Active Thread deleted before post_run(): "
"_run_state=%d", (int)_run_state);
// Notify the barrier set that a thread is being destroyed. Note that a barrier
// set might not be available if we encountered errors during bootstrapping.
BarrierSet* const barrier_set = BarrierSet::barrier_set();
if (barrier_set != NULL) {
barrier_set->on_thread_destroy(this);
}
// stack_base can be NULL if the thread is never started or exited before
// record_stack_base_and_size called. Although, we would like to ensure
// that all started threads do call record_stack_base_and_size(), there is
// not proper way to enforce that.
#if INCLUDE_NMT
if (_stack_base != NULL) {
MemTracker::release_thread_stack(stack_end(), stack_size());
#ifdef ASSERT
set_stack_base(NULL);
#endif
}
#endif // INCLUDE_NMT
// deallocate data structures
delete resource_area();
// since the handle marks are using the handle area, we have to deallocated the root
// handle mark before deallocating the thread's handle area,
assert(last_handle_mark() != NULL, "check we have an element");
delete last_handle_mark();
assert(last_handle_mark() == NULL, "check we have reached the end");
// It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
// We NULL out the fields for good hygiene.
ParkEvent::Release(_ParkEvent); _ParkEvent = NULL;
ParkEvent::Release(_MuxEvent); _MuxEvent = NULL;
delete handle_area();
delete metadata_handles();
// SR_handler uses this as a termination indicator -
// needs to happen before os::free_thread()
delete _SR_lock;
_SR_lock = NULL;
// osthread() can be NULL, if creation of thread failed.
if (osthread() != NULL) os::free_thread(osthread());
// Clear Thread::current if thread is deleting itself and it has not
// already been done. This must be done before the memory is deallocated.
// Needed to ensure JNI correctly detects non-attached threads.
if (this == Thread::current_or_null()) {
Thread::clear_thread_current();
}
CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
}
#ifdef ASSERT
// A JavaThread is considered "dangling" if it is not the current
// thread, has been added the Threads list, the system is not at a
// safepoint and the Thread is not "protected".
//
void Thread::check_for_dangling_thread_pointer(Thread *thread) {
assert(!thread->is_Java_thread() || Thread::current() == thread ||
!((JavaThread *) thread)->on_thread_list() ||
SafepointSynchronize::is_at_safepoint() ||
ThreadsSMRSupport::is_a_protected_JavaThread_with_lock((JavaThread *) thread),
"possibility of dangling Thread pointer");
}
#endif
ThreadPriority Thread::get_priority(const Thread* const thread) {
ThreadPriority priority;
// Can return an error!
(void)os::get_priority(thread, priority);
assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
return priority;
}
void Thread::set_priority(Thread* thread, ThreadPriority priority) {
debug_only(check_for_dangling_thread_pointer(thread);)
// Can return an error!
(void)os::set_priority(thread, priority);
}
void Thread::start(Thread* thread) {
// Start is different from resume in that its safety is guaranteed by context or
// being called from a Java method synchronized on the Thread object.
if (!DisableStartThread) {
if (thread->is_Java_thread()) {
// Initialize the thread state to RUNNABLE before starting this thread.
// Can not set it after the thread started because we do not know the
// exact thread state at that time. It could be in MONITOR_WAIT or
// in SLEEPING or some other state.
java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
java_lang_Thread::RUNNABLE);
}
os::start_thread(thread);
}
}
void Thread::send_async_exception(oop java_thread, oop java_throwable) {
VM_ThreadStop vm_stop(java_thread, java_throwable);
VMThread::execute(&vm_stop);
}
// Check if an external suspend request has completed (or has been
// cancelled). Returns true if the thread is externally suspended and
// false otherwise.
//
// The bits parameter returns information about the code path through
// the routine. Useful for debugging:
//
// set in is_ext_suspend_completed():
// 0x00000001 - routine was entered
// 0x00000010 - routine return false at end
// 0x00000100 - thread exited (return false)
// 0x00000200 - suspend request cancelled (return false)
// 0x00000400 - thread suspended (return true)
// 0x00001000 - thread is in a suspend equivalent state (return true)
// 0x00002000 - thread is native and walkable (return true)
// 0x00004000 - thread is native_trans and walkable (needed retry)
//
// set in wait_for_ext_suspend_completion():
// 0x00010000 - routine was entered
// 0x00020000 - suspend request cancelled before loop (return false)
// 0x00040000 - thread suspended before loop (return true)
// 0x00080000 - suspend request cancelled in loop (return false)
// 0x00100000 - thread suspended in loop (return true)
// 0x00200000 - suspend not completed during retry loop (return false)
// Helper class for tracing suspend wait debug bits.
//
// 0x00000100 indicates that the target thread exited before it could
// self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
// 0x00080000 each indicate a cancelled suspend request so they don't
// count as wait failures either.
#define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
class TraceSuspendDebugBits : public StackObj {
private:
JavaThread * jt;
bool is_wait;
bool called_by_wait; // meaningful when !is_wait
uint32_t * bits;
public:
TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
uint32_t *_bits) {
jt = _jt;
is_wait = _is_wait;
called_by_wait = _called_by_wait;
bits = _bits;
}
~TraceSuspendDebugBits() {
if (!is_wait) {
#if 1
// By default, don't trace bits for is_ext_suspend_completed() calls.
// That trace is very chatty.
return;
#else
if (!called_by_wait) {
// If tracing for is_ext_suspend_completed() is enabled, then only
// trace calls to it from wait_for_ext_suspend_completion()
return;
}
#endif
}
if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
MutexLocker ml(Threads_lock); // needed for get_thread_name()
ResourceMark rm;
tty->print_cr(
"Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
jt->get_thread_name(), *bits);
guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
}
}
}
};
#undef DEBUG_FALSE_BITS
bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay,
uint32_t *bits) {
TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
bool did_trans_retry = false; // only do thread_in_native_trans retry once
bool do_trans_retry; // flag to force the retry
*bits |= 0x00000001;
do {
do_trans_retry = false;
if (is_exiting()) {
// Thread is in the process of exiting. This is always checked
// first to reduce the risk of dereferencing a freed JavaThread.
*bits |= 0x00000100;
return false;
}
if (!is_external_suspend()) {
// Suspend request is cancelled. This is always checked before
// is_ext_suspended() to reduce the risk of a rogue resume
// confusing the thread that made the suspend request.
*bits |= 0x00000200;
return false;
}
if (is_ext_suspended()) {
// thread is suspended
*bits |= 0x00000400;
return true;
}
// Now that we no longer do hard suspends of threads running
// native code, the target thread can be changing thread state
// while we are in this routine:
//
// _thread_in_native -> _thread_in_native_trans -> _thread_blocked
//
// We save a copy of the thread state as observed at this moment
// and make our decision about suspend completeness based on the
// copy. This closes the race where the thread state is seen as
// _thread_in_native_trans in the if-thread_blocked check, but is
// seen as _thread_blocked in if-thread_in_native_trans check.
JavaThreadState save_state = thread_state();
if (save_state == _thread_blocked && is_suspend_equivalent()) {
// If the thread's state is _thread_blocked and this blocking
// condition is known to be equivalent to a suspend, then we can
// consider the thread to be externally suspended. This means that
// the code that sets _thread_blocked has been modified to do
// self-suspension if the blocking condition releases. We also
// used to check for CONDVAR_WAIT here, but that is now covered by
// the _thread_blocked with self-suspension check.
//
// Return true since we wouldn't be here unless there was still an
// external suspend request.
*bits |= 0x00001000;
return true;
} else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
// Threads running native code will self-suspend on native==>VM/Java
// transitions. If its stack is walkable (should always be the case
// unless this function is called before the actual java_suspend()
// call), then the wait is done.
*bits |= 0x00002000;
return true;
} else if (!called_by_wait && !did_trans_retry &&
save_state == _thread_in_native_trans &&
frame_anchor()->walkable()) {
// The thread is transitioning from thread_in_native to another
// thread state. check_safepoint_and_suspend_for_native_trans()
// will force the thread to self-suspend. If it hasn't gotten
// there yet we may have caught the thread in-between the native
// code check above and the self-suspend. Lucky us. If we were
// called by wait_for_ext_suspend_completion(), then it
// will be doing the retries so we don't have to.
//
// Since we use the saved thread state in the if-statement above,
// there is a chance that the thread has already transitioned to
// _thread_blocked by the time we get here. In that case, we will
// make a single unnecessary pass through the logic below. This
// doesn't hurt anything since we still do the trans retry.
*bits |= 0x00004000;
// Once the thread leaves thread_in_native_trans for another
// thread state, we break out of this retry loop. We shouldn't
// need this flag to prevent us from getting back here, but
// sometimes paranoia is good.
did_trans_retry = true;
// We wait for the thread to transition to a more usable state.
for (int i = 1; i <= SuspendRetryCount; i++) {
// We used to do an "os::yield_all(i)" call here with the intention
// that yielding would increase on each retry. However, the parameter
// is ignored on Linux which means the yield didn't scale up. Waiting
// on the SR_lock below provides a much more predictable scale up for
// the delay. It also provides a simple/direct point to check for any
// safepoint requests from the VMThread
// temporarily drops SR_lock while doing wait with safepoint check
// (if we're a JavaThread - the WatcherThread can also call this)
// and increase delay with each retry
if (Thread::current()->is_Java_thread()) {
SR_lock()->wait(i * delay);
} else {
SR_lock()->wait_without_safepoint_check(i * delay);
}
// check the actual thread state instead of what we saved above
if (thread_state() != _thread_in_native_trans) {
// the thread has transitioned to another thread state so
// try all the checks (except this one) one more time.
do_trans_retry = true;
break;
}
} // end retry loop
}
} while (do_trans_retry);
*bits |= 0x00000010;
return false;
}
// Wait for an external suspend request to complete (or be cancelled).
// Returns true if the thread is externally suspended and false otherwise.
//
bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
uint32_t *bits) {
TraceSuspendDebugBits tsdb(this, true /* is_wait */,
false /* !called_by_wait */, bits);
// local flag copies to minimize SR_lock hold time
bool is_suspended;
bool pending;
uint32_t reset_bits;
// set a marker so is_ext_suspend_completed() knows we are the caller
*bits |= 0x00010000;
// We use reset_bits to reinitialize the bits value at the top of
// each retry loop. This allows the caller to make use of any
// unused bits for their own marking purposes.
reset_bits = *bits;
{
MutexLocker ml(SR_lock(), Mutex::_no_safepoint_check_flag);
is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
delay, bits);
pending = is_external_suspend();
}
// must release SR_lock to allow suspension to complete
if (!pending) {
// A cancelled suspend request is the only false return from
// is_ext_suspend_completed() that keeps us from entering the
// retry loop.
*bits |= 0x00020000;
return false;
}
if (is_suspended) {
*bits |= 0x00040000;
return true;
}
for (int i = 1; i <= retries; i++) {
*bits = reset_bits; // reinit to only track last retry
// We used to do an "os::yield_all(i)" call here with the intention
// that yielding would increase on each retry. However, the parameter
// is ignored on Linux which means the yield didn't scale up. Waiting
// on the SR_lock below provides a much more predictable scale up for
// the delay. It also provides a simple/direct point to check for any
// safepoint requests from the VMThread
{
Thread* t = Thread::current();
MonitorLocker ml(SR_lock(),
t->is_Java_thread() ? Mutex::_safepoint_check_flag : Mutex::_no_safepoint_check_flag);
// wait with safepoint check (if we're a JavaThread - the WatcherThread
// can also call this) and increase delay with each retry
ml.wait(i * delay);
is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
delay, bits);
// It is possible for the external suspend request to be cancelled
// (by a resume) before the actual suspend operation is completed.
// Refresh our local copy to see if we still need to wait.
pending = is_external_suspend();
}
if (!pending) {
// A cancelled suspend request is the only false return from
// is_ext_suspend_completed() that keeps us from staying in the
// retry loop.
*bits |= 0x00080000;
return false;
}
if (is_suspended) {
*bits |= 0x00100000;
return true;
}
} // end retry loop
// thread did not suspend after all our retries
*bits |= 0x00200000;
return false;
}
// Called from API entry points which perform stack walking. If the
// associated JavaThread is the current thread, then wait_for_suspend
// is not used. Otherwise, it determines if we should wait for the
// "other" thread to complete external suspension. (NOTE: in future
// releases the suspension mechanism should be reimplemented so this
// is not necessary.)
//
bool
JavaThread::is_thread_fully_suspended(bool wait_for_suspend, uint32_t *bits) {
if (this != JavaThread::current()) {
// "other" threads require special handling.
if (wait_for_suspend) {
// We are allowed to wait for the external suspend to complete
// so give the other thread a chance to get suspended.
if (!wait_for_ext_suspend_completion(SuspendRetryCount,
SuspendRetryDelay, bits)) {
// Didn't make it so let the caller know.
return false;
}
}
// We aren't allowed to wait for the external suspend to complete
// so if the other thread isn't externally suspended we need to
// let the caller know.
else if (!is_ext_suspend_completed_with_lock(bits)) {
return false;
}
}
return true;
}
// GC Support
bool Thread::claim_par_threads_do(uintx claim_token) {
uintx token = _threads_do_token;
if (token != claim_token) {
uintx res = Atomic::cmpxchg(&_threads_do_token, token, claim_token);
if (res == token) {
return true;
}
guarantee(res == claim_token, "invariant");
}
return false;
}
void Thread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
active_handles()->oops_do(f);
// Do oop for ThreadShadow
f->do_oop((oop*)&_pending_exception);
handle_area()->oops_do(f);
// We scan thread local monitor lists here, and the remaining global
// monitors in ObjectSynchronizer::oops_do().
ObjectSynchronizer::thread_local_used_oops_do(this, f);
}
void Thread::metadata_handles_do(void f(Metadata*)) {
// Only walk the Handles in Thread.
if (metadata_handles() != NULL) {
for (int i = 0; i< metadata_handles()->length(); i++) {
f(metadata_handles()->at(i));
}
}
}
void Thread::print_on(outputStream* st, bool print_extended_info) const {
// get_priority assumes osthread initialized
if (osthread() != NULL) {
int os_prio;
if (os::get_native_priority(this, &os_prio) == OS_OK) {
st->print("os_prio=%d ", os_prio);
}
st->print("cpu=%.2fms ",
os::thread_cpu_time(const_cast<Thread*>(this), true) / 1000000.0
);
st->print("elapsed=%.2fs ",
_statistical_info.getElapsedTime() / 1000.0
);
if (is_Java_thread() && (PrintExtendedThreadInfo || print_extended_info)) {
size_t allocated_bytes = (size_t) const_cast<Thread*>(this)->cooked_allocated_bytes();
st->print("allocated=" SIZE_FORMAT "%s ",
byte_size_in_proper_unit(allocated_bytes),
proper_unit_for_byte_size(allocated_bytes)
);
st->print("defined_classes=" INT64_FORMAT " ", _statistical_info.getDefineClassCount());
}
st->print("tid=" INTPTR_FORMAT " ", p2i(this));
osthread()->print_on(st);
}
ThreadsSMRSupport::print_info_on(this, st);
st->print(" ");
debug_only(if (WizardMode) print_owned_locks_on(st);)
}
void Thread::print() const { print_on(tty); }
// Thread::print_on_error() is called by fatal error handler. Don't use
// any lock or allocate memory.
void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
if (is_VM_thread()) { st->print("VMThread"); }
else if (is_GC_task_thread()) { st->print("GCTaskThread"); }
else if (is_Watcher_thread()) { st->print("WatcherThread"); }
else if (is_ConcurrentGC_thread()) { st->print("ConcurrentGCThread"); }
else { st->print("Thread"); }
if (is_Named_thread()) {
st->print(" \"%s\"", name());
}
st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
p2i(stack_end()), p2i(stack_base()));
if (osthread()) {
st->print(" [id=%d]", osthread()->thread_id());
}
ThreadsSMRSupport::print_info_on(this, st);
}
void Thread::print_value_on(outputStream* st) const {
if (is_Named_thread()) {
st->print(" \"%s\" ", name());
}
st->print(INTPTR_FORMAT, p2i(this)); // print address
}
#ifdef ASSERT
void Thread::print_owned_locks_on(outputStream* st) const {
Mutex* cur = _owned_locks;
if (cur == NULL) {
st->print(" (no locks) ");
} else {
st->print_cr(" Locks owned:");
while (cur) {
cur->print_on(st);
cur = cur->next();
}
}
}
// Checks safepoint allowed and clears unhandled oops at potential safepoints.
void Thread::check_possible_safepoint() {
if (!is_Java_thread()) return;
if (_no_safepoint_count > 0) {
print_owned_locks();
fatal("Possible safepoint reached by thread that does not allow it");
}
#ifdef CHECK_UNHANDLED_OOPS
// Clear unhandled oops in JavaThreads so we get a crash right away.
clear_unhandled_oops();
#endif // CHECK_UNHANDLED_OOPS
}
void Thread::check_for_valid_safepoint_state() {
if (!is_Java_thread()) return;
// Check NoSafepointVerifier, which is implied by locks taken that can be
// shared with the VM thread. This makes sure that no locks with allow_vm_block
// are held.
check_possible_safepoint();
if (((JavaThread*)this)->thread_state() != _thread_in_vm) {
fatal("LEAF method calling lock?");
}
if (GCALotAtAllSafepoints) {
// We could enter a safepoint here and thus have a gc
InterfaceSupport::check_gc_alot();
}
}
#endif // ASSERT
bool Thread::is_in_stack(address adr) const {
assert(Thread::current() == this, "is_in_stack can only be called from current thread");
address end = os::current_stack_pointer();
// Allow non Java threads to call this without stack_base
if (_stack_base == NULL) return true;
if (stack_base() > adr && adr >= end) return true;
return false;
}
bool Thread::is_in_usable_stack(address adr) const {
size_t stack_guard_size = os::uses_stack_guard_pages() ? JavaThread::stack_guard_zone_size() : 0;
size_t usable_stack_size = _stack_size - stack_guard_size;
return ((adr < stack_base()) && (adr >= stack_base() - usable_stack_size));
}
// We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
// However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
// used for compilation in the future. If that change is made, the need for these methods
// should be revisited, and they should be removed if possible.
bool Thread::is_lock_owned(address adr) const {
return on_local_stack(adr);
}
bool Thread::set_as_starting_thread() {
assert(_starting_thread == NULL, "already initialized: "
"_starting_thread=" INTPTR_FORMAT, p2i(_starting_thread));
// NOTE: this must be called inside the main thread.
DEBUG_ONLY(_starting_thread = this;)
return os::create_main_thread((JavaThread*)this);
}
static void initialize_class(Symbol* class_name, TRAPS) {
Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
InstanceKlass::cast(klass)->initialize(CHECK);
}
// Creates the initial ThreadGroup
static Handle create_initial_thread_group(TRAPS) {
Handle system_instance = JavaCalls::construct_new_instance(
SystemDictionary::ThreadGroup_klass(),
vmSymbols::void_method_signature(),
CHECK_NH);
Universe::set_system_thread_group(system_instance());
Handle string = java_lang_String::create_from_str("main", CHECK_NH);
Handle main_instance = JavaCalls::construct_new_instance(
SystemDictionary::ThreadGroup_klass(),
vmSymbols::threadgroup_string_void_signature(),
system_instance,
string,
CHECK_NH);
return main_instance;
}
// Creates the initial Thread
static oop create_initial_thread(Handle thread_group, JavaThread* thread,
TRAPS) {
InstanceKlass* ik = SystemDictionary::Thread_klass();
assert(ik->is_initialized(), "must be");
instanceHandle thread_oop = ik->allocate_instance_handle(CHECK_NULL);
// Cannot use JavaCalls::construct_new_instance because the java.lang.Thread
// constructor calls Thread.current(), which must be set here for the
// initial thread.
java_lang_Thread::set_thread(thread_oop(), thread);
java_lang_Thread::set_priority(thread_oop(), NormPriority);
thread->set_threadObj(thread_oop());
Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
JavaValue result(T_VOID);
JavaCalls::call_special(&result, thread_oop,
ik,
vmSymbols::object_initializer_name(),
vmSymbols::threadgroup_string_void_signature(),
thread_group,
string,
CHECK_NULL);
return thread_oop();
}
char java_runtime_name[128] = "";
char java_runtime_version[128] = "";
char java_runtime_vendor_version[128] = "";
char java_runtime_vendor_vm_bug_url[128] = "";
// extract the JRE name from java.lang.VersionProps.java_runtime_name
static const char* get_java_runtime_name(TRAPS) {
Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
Handle(), Handle(), CHECK_AND_CLEAR_NULL);
fieldDescriptor fd;
bool found = k != NULL &&
InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_name_name(),
vmSymbols::string_signature(), &fd);
if (found) {
oop name_oop = k->java_mirror()->obj_field(fd.offset());
if (name_oop == NULL) {
return NULL;
}
const char* name = java_lang_String::as_utf8_string(name_oop,
java_runtime_name,
sizeof(java_runtime_name));
return name;
} else {
return NULL;
}
}
// extract the JRE version from java.lang.VersionProps.java_runtime_version
static const char* get_java_runtime_version(TRAPS) {
Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
Handle(), Handle(), CHECK_AND_CLEAR_NULL);
fieldDescriptor fd;
bool found = k != NULL &&
InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_version_name(),
vmSymbols::string_signature(), &fd);
if (found) {
oop name_oop = k->java_mirror()->obj_field(fd.offset());
if (name_oop == NULL) {
return NULL;
}
const char* name = java_lang_String::as_utf8_string(name_oop,
java_runtime_version,
sizeof(java_runtime_version));
return name;
} else {
return NULL;
}
}
// extract the JRE vendor version from java.lang.VersionProps.VENDOR_VERSION
static const char* get_java_runtime_vendor_version(TRAPS) {
Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
Handle(), Handle(), CHECK_AND_CLEAR_NULL);
fieldDescriptor fd;
bool found = k != NULL &&
InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_vendor_version_name(),
vmSymbols::string_signature(), &fd);
if (found) {
oop name_oop = k->java_mirror()->obj_field(fd.offset());
if (name_oop == NULL) {
return NULL;
}
const char* name = java_lang_String::as_utf8_string(name_oop,
java_runtime_vendor_version,
sizeof(java_runtime_vendor_version));
return name;
} else {
return NULL;
}
}
// extract the JRE vendor VM bug URL from java.lang.VersionProps.VENDOR_URL_VM_BUG
static const char* get_java_runtime_vendor_vm_bug_url(TRAPS) {
Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
Handle(), Handle(), CHECK_AND_CLEAR_NULL);
fieldDescriptor fd;
bool found = k != NULL &&
InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_vendor_vm_bug_url_name(),
vmSymbols::string_signature(), &fd);
if (found) {
oop name_oop = k->java_mirror()->obj_field(fd.offset());
if (name_oop == NULL) {
return NULL;
}
const char* name = java_lang_String::as_utf8_string(name_oop,
java_runtime_vendor_vm_bug_url,
sizeof(java_runtime_vendor_vm_bug_url));
return name;
} else {
return NULL;
}
}
// General purpose hook into Java code, run once when the VM is initialized.
// The Java library method itself may be changed independently from the VM.
static void call_postVMInitHook(TRAPS) {
Klass* klass = SystemDictionary::resolve_or_null(vmSymbols::jdk_internal_vm_PostVMInitHook(), THREAD);
if (klass != NULL) {
JavaValue result(T_VOID);
JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
vmSymbols::void_method_signature(),
CHECK);
}
}
void JavaThread::allocate_threadObj(Handle thread_group, const char* thread_name,
bool daemon, TRAPS) {
assert(thread_group.not_null(), "thread group should be specified");
assert(threadObj() == NULL, "should only create Java thread object once");
InstanceKlass* ik = SystemDictionary::Thread_klass();
assert(ik->is_initialized(), "must be");
instanceHandle thread_oop = ik->allocate_instance_handle(CHECK);
// We are called from jni_AttachCurrentThread/jni_AttachCurrentThreadAsDaemon.
// We cannot use JavaCalls::construct_new_instance because the java.lang.Thread
// constructor calls Thread.current(), which must be set here.
java_lang_Thread::set_thread(thread_oop(), this);
java_lang_Thread::set_priority(thread_oop(), NormPriority);
set_threadObj(thread_oop());
JavaValue result(T_VOID);
if (thread_name != NULL) {
Handle name = java_lang_String::create_from_str(thread_name, CHECK);
// Thread gets assigned specified name and null target
JavaCalls::call_special(&result,
thread_oop,
ik,
vmSymbols::object_initializer_name(),
vmSymbols::threadgroup_string_void_signature(),
thread_group,
name,
THREAD);
} else {
// Thread gets assigned name "Thread-nnn" and null target
// (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
JavaCalls::call_special(&result,
thread_oop,
ik,
vmSymbols::object_initializer_name(),
vmSymbols::threadgroup_runnable_void_signature(),
thread_group,
Handle(),
THREAD);
}
if (daemon) {
java_lang_Thread::set_daemon(thread_oop());
}
if (HAS_PENDING_EXCEPTION) {
return;
}
Klass* group = SystemDictionary::ThreadGroup_klass();
Handle threadObj(THREAD, this->threadObj());
JavaCalls::call_special(&result,
thread_group,
group,
vmSymbols::add_method_name(),
vmSymbols::thread_void_signature(),
threadObj, // Arg 1
THREAD);
}
// List of all NonJavaThreads and safe iteration over that list.
class NonJavaThread::List {
public:
NonJavaThread* volatile _head;
SingleWriterSynchronizer _protect;
List() : _head(NULL), _protect() {}
};
NonJavaThread::List NonJavaThread::_the_list;
NonJavaThread::Iterator::Iterator() :
_protect_enter(_the_list._protect.enter()),
_current(Atomic::load_acquire(&_the_list._head))
{}
NonJavaThread::Iterator::~Iterator() {
_the_list._protect.exit(_protect_enter);
}
void NonJavaThread::Iterator::step() {
assert(!end(), "precondition");
_current = Atomic::load_acquire(&_current->_next);
}
NonJavaThread::NonJavaThread() : Thread(), _next(NULL) {
assert(BarrierSet::barrier_set() != NULL, "NonJavaThread created too soon!");
}
NonJavaThread::~NonJavaThread() { }
void NonJavaThread::add_to_the_list() {
MutexLocker ml(NonJavaThreadsList_lock, Mutex::_no_safepoint_check_flag);
// Initialize BarrierSet-related data before adding to list.
BarrierSet::barrier_set()->on_thread_attach(this);
Atomic::release_store(&_next, _the_list._head);
Atomic::release_store(&_the_list._head, this);
}
void NonJavaThread::remove_from_the_list() {
{
MutexLocker ml(NonJavaThreadsList_lock, Mutex::_no_safepoint_check_flag);
// Cleanup BarrierSet-related data before removing from list.
BarrierSet::barrier_set()->on_thread_detach(this);
NonJavaThread* volatile* p = &_the_list._head;
for (NonJavaThread* t = *p; t != NULL; p = &t->_next, t = *p) {
if (t == this) {
*p = _next;
break;
}
}
}
// Wait for any in-progress iterators. Concurrent synchronize is not
// allowed, so do it while holding a dedicated lock. Outside and distinct
// from NJTList_lock in case an iteration attempts to lock it.
MutexLocker ml(NonJavaThreadsListSync_lock, Mutex::_no_safepoint_check_flag);
_the_list._protect.synchronize();
_next = NULL; // Safe to drop the link now.
}
void NonJavaThread::pre_run() {
add_to_the_list();
// This is slightly odd in that NamedThread is a subclass, but
// in fact name() is defined in Thread
assert(this->name() != NULL, "thread name was not set before it was started");
this->set_native_thread_name(this->name());
}
void NonJavaThread::post_run() {
JFR_ONLY(Jfr::on_thread_exit(this);)
remove_from_the_list();
// Ensure thread-local-storage is cleared before termination.
Thread::clear_thread_current();
}
// NamedThread -- non-JavaThread subclasses with multiple
// uniquely named instances should derive from this.
NamedThread::NamedThread() :
NonJavaThread(),
_name(NULL),
_processed_thread(NULL),
_gc_id(GCId::undefined())
{}
NamedThread::~NamedThread() {
FREE_C_HEAP_ARRAY(char, _name);
}
void NamedThread::set_name(const char* format, ...) {
guarantee(_name == NULL, "Only get to set name once.");
_name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
va_list ap;
va_start(ap, format);
jio_vsnprintf(_name, max_name_len, format, ap);
va_end(ap);
}
void NamedThread::print_on(outputStream* st) const {
st->print("\"%s\" ", name());
Thread::print_on(st);
st->cr();
}
// ======= WatcherThread ========
// The watcher thread exists to simulate timer interrupts. It should
// be replaced by an abstraction over whatever native support for
// timer interrupts exists on the platform.
WatcherThread* WatcherThread::_watcher_thread = NULL;
bool WatcherThread::_startable = false;
volatile bool WatcherThread::_should_terminate = false;
WatcherThread::WatcherThread() : NonJavaThread() {
assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
if (os::create_thread(this, os::watcher_thread)) {
_watcher_thread = this;
// Set the watcher thread to the highest OS priority which should not be
// used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
// is created. The only normal thread using this priority is the reference
// handler thread, which runs for very short intervals only.
// If the VMThread's priority is not lower than the WatcherThread profiling
// will be inaccurate.
os::set_priority(this, MaxPriority);
if (!DisableStartThread) {
os::start_thread(this);
}
}
}
int WatcherThread::sleep() const {
// The WatcherThread does not participate in the safepoint protocol
// for the PeriodicTask_lock because it is not a JavaThread.
MonitorLocker ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
if (_should_terminate) {
// check for termination before we do any housekeeping or wait
return 0; // we did not sleep.
}
// remaining will be zero if there are no tasks,
// causing the WatcherThread to sleep until a task is
// enrolled
int remaining = PeriodicTask::time_to_wait();
int time_slept = 0;
// we expect this to timeout - we only ever get unparked when
// we should terminate or when a new task has been enrolled
OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
jlong time_before_loop = os::javaTimeNanos();
while (true) {
bool timedout = ml.wait(remaining);
jlong now = os::javaTimeNanos();
if (remaining == 0) {
// if we didn't have any tasks we could have waited for a long time
// consider the time_slept zero and reset time_before_loop
time_slept = 0;
time_before_loop = now;
} else {
// need to recalculate since we might have new tasks in _tasks
time_slept = (int) ((now - time_before_loop) / 1000000);
}
// Change to task list or spurious wakeup of some kind
if (timedout || _should_terminate) {
break;
}
remaining = PeriodicTask::time_to_wait();
if (remaining == 0) {
// Last task was just disenrolled so loop around and wait until
// another task gets enrolled
continue;
}
remaining -= time_slept;
if (remaining <= 0) {
break;
}
}
return time_slept;
}
void WatcherThread::run() {
assert(this == watcher_thread(), "just checking");
this->set_active_handles(JNIHandleBlock::allocate_block());
while (true) {
assert(watcher_thread() == Thread::current(), "thread consistency check");
assert(watcher_thread() == this, "thread consistency check");
// Calculate how long it'll be until the next PeriodicTask work
// should be done, and sleep that amount of time.
int time_waited = sleep();
if (VMError::is_error_reported()) {
// A fatal error has happened, the error handler(VMError::report_and_die)
// should abort JVM after creating an error log file. However in some
// rare cases, the error handler itself might deadlock. Here periodically
// check for error reporting timeouts, and if it happens, just proceed to
// abort the VM.
// This code is in WatcherThread because WatcherThread wakes up
// periodically so the fatal error handler doesn't need to do anything;
// also because the WatcherThread is less likely to crash than other
// threads.
for (;;) {
// Note: we use naked sleep in this loop because we want to avoid using
// any kind of VM infrastructure which may be broken at this point.
if (VMError::check_timeout()) {
// We hit error reporting timeout. Error reporting was interrupted and
// will be wrapping things up now (closing files etc). Give it some more
// time, then quit the VM.
os::naked_short_sleep(200);
// Print a message to stderr.
fdStream err(defaultStream::output_fd());
err.print_raw_cr("# [ timer expired, abort... ]");
// skip atexit/vm_exit/vm_abort hooks
os::die();
}
// Wait a second, then recheck for timeout.
os::naked_short_sleep(999);
}
}
if (_should_terminate) {
// check for termination before posting the next tick
break;
}
PeriodicTask::real_time_tick(time_waited);
}
// Signal that it is terminated
{
MutexLocker mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
_watcher_thread = NULL;
Terminator_lock->notify_all();
}
}
void WatcherThread::start() {
assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
if (watcher_thread() == NULL && _startable) {
_should_terminate = false;
// Create the single instance of WatcherThread
new WatcherThread();
}
}
void WatcherThread::make_startable() {
assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
_startable = true;
}
void WatcherThread::stop() {
{
// Follow normal safepoint aware lock enter protocol since the
// WatcherThread is stopped by another JavaThread.
MutexLocker ml(PeriodicTask_lock);
_should_terminate = true;
WatcherThread* watcher = watcher_thread();
if (watcher != NULL) {
// unpark the WatcherThread so it can see that it should terminate
watcher->unpark();
}
}
MonitorLocker mu(Terminator_lock);
while (watcher_thread() != NULL) {
// This wait should make safepoint checks, wait without a timeout,
// and wait as a suspend-equivalent condition.
mu.wait(0, Mutex::_as_suspend_equivalent_flag);
}
}
void WatcherThread::unpark() {
assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
PeriodicTask_lock->notify();
}
void WatcherThread::print_on(outputStream* st) const {
st->print("\"%s\" ", name());
Thread::print_on(st);
st->cr();
}
// ======= JavaThread ========
#if INCLUDE_JVMCI
jlong* JavaThread::_jvmci_old_thread_counters;
bool jvmci_counters_include(JavaThread* thread) {
return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread();
}
void JavaThread::collect_counters(jlong* array, int length) {
assert(length == JVMCICounterSize, "wrong value");
for (int i = 0; i < length; i++) {
array[i] = _jvmci_old_thread_counters[i];
}
for (JavaThreadIteratorWithHandle jtiwh; JavaThread *tp = jtiwh.next(); ) {
if (jvmci_counters_include(tp)) {
for (int i = 0; i < length; i++) {
array[i] += tp->_jvmci_counters[i];
}
}
}
}
// Attempt to enlarge the array for per thread counters.
jlong* resize_counters_array(jlong* old_counters, int current_size, int new_size) {
jlong* new_counters = NEW_C_HEAP_ARRAY(jlong, new_size, mtJVMCI);
if (old_counters == NULL) {
old_counters = new_counters;
memset(old_counters, 0, sizeof(jlong) * new_size);
} else {
for (int i = 0; i < MIN2((int) current_size, new_size); i++) {
new_counters[i] = old_counters[i];
}
if (new_size > current_size) {
memset(new_counters + current_size, 0, sizeof(jlong) * (new_size - current_size));
}
FREE_C_HEAP_ARRAY(jlong, old_counters);
}
return new_counters;
}
// Attempt to enlarge the array for per thread counters.
void JavaThread::resize_counters(int current_size, int new_size) {
_jvmci_counters = resize_counters_array(_jvmci_counters, current_size, new_size);
}
class VM_JVMCIResizeCounters : public VM_Operation {
private:
int _new_size;
public:
VM_JVMCIResizeCounters(int new_size) : _new_size(new_size) { }
VMOp_Type type() const { return VMOp_JVMCIResizeCounters; }
bool allow_nested_vm_operations() const { return true; }
void doit() {
// Resize the old thread counters array
jlong* new_counters = resize_counters_array(JavaThread::_jvmci_old_thread_counters, JVMCICounterSize, _new_size);
JavaThread::_jvmci_old_thread_counters = new_counters;
// Now resize each threads array
for (JavaThreadIteratorWithHandle jtiwh; JavaThread *tp = jtiwh.next(); ) {
tp->resize_counters(JVMCICounterSize, _new_size);
}
JVMCICounterSize = _new_size;
}
};
void JavaThread::resize_all_jvmci_counters(int new_size) {
VM_JVMCIResizeCounters op(new_size);
VMThread::execute(&op);
}
#endif // INCLUDE_JVMCI
// A JavaThread is a normal Java thread
void JavaThread::initialize() {
// Initialize fields
set_saved_exception_pc(NULL);
set_threadObj(NULL);
_anchor.clear();
set_entry_point(NULL);
set_jni_functions(jni_functions());
set_callee_target(NULL);
set_vm_result(NULL);
set_vm_result_2(NULL);
set_vframe_array_head(NULL);
set_vframe_array_last(NULL);
set_deferred_locals(NULL);
set_deopt_mark(NULL);
set_deopt_compiled_method(NULL);
set_monitor_chunks(NULL);
_on_thread_list = false;
set_thread_state(_thread_new);
_terminated = _not_terminated;
_array_for_gc = NULL;
_suspend_equivalent = false;
_in_deopt_handler = 0;
_doing_unsafe_access = false;
_stack_guard_state = stack_guard_unused;
#if INCLUDE_JVMCI
_pending_monitorenter = false;
_pending_deoptimization = -1;
_pending_failed_speculation = 0;
_pending_transfer_to_interpreter = false;
_in_retryable_allocation = false;
_jvmci._alternate_call_target = NULL;
assert(_jvmci._implicit_exception_pc == NULL, "must be");
_jvmci_counters = NULL;
if (JVMCICounterSize > 0) {
resize_counters(0, (int) JVMCICounterSize);
}
#endif // INCLUDE_JVMCI
_reserved_stack_activation = NULL; // stack base not known yet
(void)const_cast<oop&>(_exception_oop = oop(NULL));
_exception_pc = 0;
_exception_handler_pc = 0;
_is_method_handle_return = 0;
_jvmti_thread_state= NULL;
_should_post_on_exceptions_flag = JNI_FALSE;
_interp_only_mode = 0;
_special_runtime_exit_condition = _no_async_condition;
_pending_async_exception = NULL;
_thread_stat = NULL;
_thread_stat = new ThreadStatistics();
_jni_active_critical = 0;
_pending_jni_exception_check_fn = NULL;
_do_not_unlock_if_synchronized = false;
_cached_monitor_info = NULL;
_parker = Parker::Allocate(this);
_SleepEvent = ParkEvent::Allocate(this);
// Setup safepoint state info for this thread
ThreadSafepointState::create(this);
debug_only(_java_call_counter = 0);
// JVMTI PopFrame support
_popframe_condition = popframe_inactive;
_popframe_preserved_args = NULL;
_popframe_preserved_args_size = 0;
_frames_to_pop_failed_realloc = 0;
if (SafepointMechanism::uses_thread_local_poll()) {
SafepointMechanism::initialize_header(this);
}
_class_to_be_initialized = NULL;
pd_initialize();
}
JavaThread::JavaThread(bool is_attaching_via_jni) :
Thread() {
initialize();
if (is_attaching_via_jni) {
_jni_attach_state = _attaching_via_jni;
} else {
_jni_attach_state = _not_attaching_via_jni;
}
assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
}
// interrupt support
void JavaThread::interrupt() {
debug_only(check_for_dangling_thread_pointer(this);)
// For Windows _interrupt_event
osthread()->set_interrupted(true);
// For Thread.sleep
_SleepEvent->unpark();
// For JSR166 LockSupport.park
parker()->unpark();
// For ObjectMonitor and JvmtiRawMonitor
_ParkEvent->unpark();
}
bool JavaThread::is_interrupted(bool clear_interrupted) {
debug_only(check_for_dangling_thread_pointer(this);)
if (threadObj() == NULL) {
// If there is no j.l.Thread then it is impossible to have
// been interrupted. We can find NULL during VM initialization
// or when a JNI thread is still in the process of attaching.
// In such cases this must be the current thread.
assert(this == Thread::current(), "invariant");
return false;
}
bool interrupted = java_lang_Thread::interrupted(threadObj());
// NOTE that since there is no "lock" around the interrupt and
// is_interrupted operations, there is the possibility that the
// interrupted flag will be "false" but that the
// low-level events will be in the signaled state. This is
// intentional. The effect of this is that Object.wait() and
// LockSupport.park() will appear to have a spurious wakeup, which
// is allowed and not harmful, and the possibility is so rare that
// it is not worth the added complexity to add yet another lock.
// For the sleep event an explicit reset is performed on entry
// to JavaThread::sleep, so there is no early return. It has also been
// recommended not to put the interrupted flag into the "event"
// structure because it hides the issue.
// Also, because there is no lock, we must only clear the interrupt
// state if we are going to report that we were interrupted; otherwise
// an interrupt that happens just after we read the field would be lost.
if (interrupted && clear_interrupted) {
assert(this == Thread::current(), "only the current thread can clear");
java_lang_Thread::set_interrupted(threadObj(), false);
osthread()->set_interrupted(false);
}
return interrupted;
}
bool JavaThread::reguard_stack(address cur_sp) {
if (_stack_guard_state != stack_guard_yellow_reserved_disabled
&& _stack_guard_state != stack_guard_reserved_disabled) {
return true; // Stack already guarded or guard pages not needed.
}
if (register_stack_overflow()) {
// For those architectures which have separate register and
// memory stacks, we must check the register stack to see if
// it has overflowed.
return false;
}
// Java code never executes within the yellow zone: the latter is only
// there to provoke an exception during stack banging. If java code
// is executing there, either StackShadowPages should be larger, or
// some exception code in c1, c2 or the interpreter isn't unwinding
// when it should.
guarantee(cur_sp > stack_reserved_zone_base(),
"not enough space to reguard - increase StackShadowPages");
if (_stack_guard_state == stack_guard_yellow_reserved_disabled) {
enable_stack_yellow_reserved_zone();
if (reserved_stack_activation() != stack_base()) {
set_reserved_stack_activation(stack_base());
}
} else if (_stack_guard_state == stack_guard_reserved_disabled) {
set_reserved_stack_activation(stack_base());
enable_stack_reserved_zone();
}
return true;
}
bool JavaThread::reguard_stack(void) {
return reguard_stack(os::current_stack_pointer());
}
void JavaThread::block_if_vm_exited() {
if (_terminated == _vm_exited) {
// _vm_exited is set at safepoint, and Threads_lock is never released
// we will block here forever.
// Here we can be doing a jump from a safe state to an unsafe state without
// proper transition, but it happens after the final safepoint has begun.
set_thread_state(_thread_in_vm);
Threads_lock->lock();
ShouldNotReachHere();
}
}
// Remove this ifdef when C1 is ported to the compiler interface.
static void compiler_thread_entry(JavaThread* thread, TRAPS);
static void sweeper_thread_entry(JavaThread* thread, TRAPS);
JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
Thread() {
initialize();
_jni_attach_state = _not_attaching_via_jni;
set_entry_point(entry_point);
// Create the native thread itself.
// %note runtime_23
os::ThreadType thr_type = os::java_thread;
thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
os::java_thread;
os::create_thread(this, thr_type, stack_sz);
// The _osthread may be NULL here because we ran out of memory (too many threads active).
// We need to throw and OutOfMemoryError - however we cannot do this here because the caller
// may hold a lock and all locks must be unlocked before throwing the exception (throwing
// the exception consists of creating the exception object & initializing it, initialization
// will leave the VM via a JavaCall and then all locks must be unlocked).
//
// The thread is still suspended when we reach here. Thread must be explicit started
// by creator! Furthermore, the thread must also explicitly be added to the Threads list
// by calling Threads:add. The reason why this is not done here, is because the thread
// object must be fully initialized (take a look at JVM_Start)
}
JavaThread::~JavaThread() {
// JSR166 -- return the parker to the free list
Parker::Release(_parker);
_parker = NULL;
// Return the sleep event to the free list
ParkEvent::Release(_SleepEvent);
_SleepEvent = NULL;
// Free any remaining previous UnrollBlock
vframeArray* old_array = vframe_array_last();
if (old_array != NULL) {
Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
old_array->set_unroll_block(NULL);
delete old_info;
delete old_array;
}
GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
if (deferred != NULL) {
// This can only happen if thread is destroyed before deoptimization occurs.
assert(deferred->length() != 0, "empty array!");
do {
jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
deferred->remove_at(0);
// individual jvmtiDeferredLocalVariableSet are CHeapObj's
delete dlv;
} while (deferred->length() != 0);
delete deferred;
}
// All Java related clean up happens in exit
ThreadSafepointState::destroy(this);
if (_thread_stat != NULL) delete _thread_stat;
#if INCLUDE_JVMCI
if (JVMCICounterSize > 0) {
if (jvmci_counters_include(this)) {
for (int i = 0; i < JVMCICounterSize; i++) {
_jvmci_old_thread_counters[i] += _jvmci_counters[i];
}
}
FREE_C_HEAP_ARRAY(jlong, _jvmci_counters);
}
#endif // INCLUDE_JVMCI
}
// First JavaThread specific code executed by a new Java thread.
void JavaThread::pre_run() {
// empty - see comments in run()
}
// The main routine called by a new Java thread. This isn't overridden
// by subclasses, instead different subclasses define a different "entry_point"
// which defines the actual logic for that kind of thread.
void JavaThread::run() {
// initialize thread-local alloc buffer related fields
this->initialize_tlab();
// Used to test validity of stack trace backs.
// This can't be moved into pre_run() else we invalidate
// the requirement that thread_main_inner is lower on
// the stack. Consequently all the initialization logic
// stays here in run() rather than pre_run().
this->record_base_of_stack_pointer();
this->create_stack_guard_pages();
this->cache_global_variables();
// Thread is now sufficiently initialized to be handled by the safepoint code as being
// in the VM. Change thread state from _thread_new to _thread_in_vm
ThreadStateTransition::transition(this, _thread_new, _thread_in_vm);
// Before a thread is on the threads list it is always safe, so after leaving the
// _thread_new we should emit a instruction barrier. The distance to modified code
// from here is probably far enough, but this is consistent and safe.
OrderAccess::cross_modify_fence();
assert(JavaThread::current() == this, "sanity check");
assert(!Thread::current()->owns_locks(), "sanity check");
DTRACE_THREAD_PROBE(start, this);
// This operation might block. We call that after all safepoint checks for a new thread has
// been completed.
this->set_active_handles(JNIHandleBlock::allocate_block());
if (JvmtiExport::should_post_thread_life()) {
JvmtiExport::post_thread_start(this);
}
// We call another function to do the rest so we are sure that the stack addresses used
// from there will be lower than the stack base just computed.
thread_main_inner();
}
void JavaThread::thread_main_inner() {
assert(JavaThread::current() == this, "sanity check");
assert(this->threadObj() != NULL, "just checking");
// Execute thread entry point unless this thread has a pending exception
// or has been stopped before starting.
// Note: Due to JVM_StopThread we can have pending exceptions already!
if (!this->has_pending_exception() &&
!java_lang_Thread::is_stillborn(this->threadObj())) {
{
ResourceMark rm(this);
this->set_native_thread_name(this->get_thread_name());
}
HandleMark hm(this);
this->entry_point()(this, this);
}
DTRACE_THREAD_PROBE(stop, this);
// Cleanup is handled in post_run()
}
// Shared teardown for all JavaThreads
void JavaThread::post_run() {
this->exit(false);
// Defer deletion to here to ensure 'this' is still referenceable in call_run
// for any shared tear-down.
this->smr_delete();
}
static void ensure_join(JavaThread* thread) {
// We do not need to grab the Threads_lock, since we are operating on ourself.
Handle threadObj(thread, thread->threadObj());
assert(threadObj.not_null(), "java thread object must exist");
ObjectLocker lock(threadObj, thread);
// Ignore pending exception (ThreadDeath), since we are exiting anyway
thread->clear_pending_exception();
// Thread is exiting. So set thread_status field in java.lang.Thread class to TERMINATED.
java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
// Clear the native thread instance - this makes isAlive return false and allows the join()
// to complete once we've done the notify_all below
java_lang_Thread::set_thread(threadObj(), NULL);
lock.notify_all(thread);
// Ignore pending exception (ThreadDeath), since we are exiting anyway
thread->clear_pending_exception();
}
static bool is_daemon(oop threadObj) {
return (threadObj != NULL && java_lang_Thread::is_daemon(threadObj));
}
// For any new cleanup additions, please check to see if they need to be applied to
// cleanup_failed_attach_current_thread as well.
void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
assert(this == JavaThread::current(), "thread consistency check");
elapsedTimer _timer_exit_phase1;
elapsedTimer _timer_exit_phase2;
elapsedTimer _timer_exit_phase3;
elapsedTimer _timer_exit_phase4;
if (log_is_enabled(Debug, os, thread, timer)) {
_timer_exit_phase1.start();
}
HandleMark hm(this);
Handle uncaught_exception(this, this->pending_exception());
this->clear_pending_exception();
Handle threadObj(this, this->threadObj());
assert(threadObj.not_null(), "Java thread object should be created");
// FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
{
EXCEPTION_MARK;
CLEAR_PENDING_EXCEPTION;
}
if (!destroy_vm) {
if (uncaught_exception.not_null()) {
EXCEPTION_MARK;
// Call method Thread.dispatchUncaughtException().
Klass* thread_klass = SystemDictionary::Thread_klass();
JavaValue result(T_VOID);
JavaCalls::call_virtual(&result,
threadObj, thread_klass,
vmSymbols::dispatchUncaughtException_name(),
vmSymbols::throwable_void_signature(),
uncaught_exception,
THREAD);
if (HAS_PENDING_EXCEPTION) {
ResourceMark rm(this);
jio_fprintf(defaultStream::error_stream(),
"\nException: %s thrown from the UncaughtExceptionHandler"
" in thread \"%s\"\n",
pending_exception()->klass()->external_name(),
get_thread_name());
CLEAR_PENDING_EXCEPTION;
}
}
JFR_ONLY(Jfr::on_java_thread_dismantle(this);)
// Call Thread.exit(). We try 3 times in case we got another Thread.stop during
// the execution of the method. If that is not enough, then we don't really care. Thread.stop
// is deprecated anyhow.
if (!is_Compiler_thread()) {
int count = 3;
while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
EXCEPTION_MARK;
JavaValue result(T_VOID);
Klass* thread_klass = SystemDictionary::Thread_klass();
JavaCalls::call_virtual(&result,
threadObj, thread_klass,
vmSymbols::exit_method_name(),
vmSymbols::void_method_signature(),
THREAD);
CLEAR_PENDING_EXCEPTION;
}
}
// notify JVMTI
if (JvmtiExport::should_post_thread_life()) {
JvmtiExport::post_thread_end(this);
}
// We have notified the agents that we are exiting, before we go on,
// we must check for a pending external suspend request and honor it
// in order to not surprise the thread that made the suspend request.
while (true) {
{
MutexLocker ml(SR_lock(), Mutex::_no_safepoint_check_flag);
if (!is_external_suspend()) {
set_terminated(_thread_exiting);
ThreadService::current_thread_exiting(this, is_daemon(threadObj()));
break;
}
// Implied else:
// Things get a little tricky here. We have a pending external
// suspend request, but we are holding the SR_lock so we
// can't just self-suspend. So we temporarily drop the lock
// and then self-suspend.
}
ThreadBlockInVM tbivm(this);
java_suspend_self();
// We're done with this suspend request, but we have to loop around
// and check again. Eventually we will get SR_lock without a pending
// external suspend request and will be able to mark ourselves as
// exiting.
}
// no more external suspends are allowed at this point
} else {
assert(!is_terminated() && !is_exiting(), "must not be exiting");
// before_exit() has already posted JVMTI THREAD_END events
}
if (log_is_enabled(Debug, os, thread, timer)) {
_timer_exit_phase1.stop();
_timer_exit_phase2.start();
}
// Capture daemon status before the thread is marked as terminated.
bool daemon = is_daemon(threadObj());
// Notify waiters on thread object. This has to be done after exit() is called
// on the thread (if the thread is the last thread in a daemon ThreadGroup the
// group should have the destroyed bit set before waiters are notified).
ensure_join(this);
assert(!this->has_pending_exception(), "ensure_join should have cleared");
if (log_is_enabled(Debug, os, thread, timer)) {
_timer_exit_phase2.stop();
_timer_exit_phase3.start();
}
// 6282335 JNI DetachCurrentThread spec states that all Java monitors
// held by this thread must be released. The spec does not distinguish
// between JNI-acquired and regular Java monitors. We can only see
// regular Java monitors here if monitor enter-exit matching is broken.
//
// ensure_join() ignores IllegalThreadStateExceptions, and so does
// ObjectSynchronizer::release_monitors_owned_by_thread().
if (exit_type == jni_detach) {
// Sanity check even though JNI DetachCurrentThread() would have
// returned JNI_ERR if there was a Java frame. JavaThread exit
// should be done executing Java code by the time we get here.
assert(!this->has_last_Java_frame(),
"should not have a Java frame when detaching or exiting");
ObjectSynchronizer::release_monitors_owned_by_thread(this);
assert(!this->has_pending_exception(), "release_monitors should have cleared");
}
// These things needs to be done while we are still a Java Thread. Make sure that thread
// is in a consistent state, in case GC happens
JFR_ONLY(Jfr::on_thread_exit(this);)
if (active_handles() != NULL) {
JNIHandleBlock* block = active_handles();
set_active_handles(NULL);
JNIHandleBlock::release_block(block);
}
if (free_handle_block() != NULL) {
JNIHandleBlock* block = free_handle_block();
set_free_handle_block(NULL);
JNIHandleBlock::release_block(block);
}
// These have to be removed while this is still a valid thread.
remove_stack_guard_pages();
if (UseTLAB) {
tlab().retire();
}
if (JvmtiEnv::environments_might_exist()) {
JvmtiExport::cleanup_thread(this);
}
// We must flush any deferred card marks and other various GC barrier
// related buffers (e.g. G1 SATB buffer and G1 dirty card queue buffer)
// before removing a thread from the list of active threads.
BarrierSet::barrier_set()->on_thread_detach(this);
log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
exit_type == JavaThread::normal_exit ? "exiting" : "detaching",
os::current_thread_id());
if (log_is_enabled(Debug, os, thread, timer)) {
_timer_exit_phase3.stop();
_timer_exit_phase4.start();
}
// Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
Threads::remove(this, daemon);
if (log_is_enabled(Debug, os, thread, timer)) {
_timer_exit_phase4.stop();
ResourceMark rm(this);
log_debug(os, thread, timer)("name='%s'"
", exit-phase1=" JLONG_FORMAT
", exit-phase2=" JLONG_FORMAT
", exit-phase3=" JLONG_FORMAT
", exit-phase4=" JLONG_FORMAT,
get_thread_name(),
_timer_exit_phase1.milliseconds(),
_timer_exit_phase2.milliseconds(),
_timer_exit_phase3.milliseconds(),
_timer_exit_phase4.milliseconds());
}
}
void JavaThread::cleanup_failed_attach_current_thread(bool is_daemon) {
if (active_handles() != NULL) {
JNIHandleBlock* block = active_handles();
set_active_handles(NULL);
JNIHandleBlock::release_block(block);
}
if (free_handle_block() != NULL) {
JNIHandleBlock* block = free_handle_block();
set_free_handle_block(NULL);
JNIHandleBlock::release_block(block);
}
// These have to be removed while this is still a valid thread.
remove_stack_guard_pages();
if (UseTLAB) {
tlab().retire();
}
BarrierSet::barrier_set()->on_thread_detach(this);
Threads::remove(this, is_daemon);
this->smr_delete();
}
JavaThread* JavaThread::active() {
Thread* thread = Thread::current();
if (thread->is_Java_thread()) {
return (JavaThread*) thread;
} else {
assert(thread->is_VM_thread(), "this must be a vm thread");
VM_Operation* op = ((VMThread*) thread)->vm_operation();
JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
assert(ret->is_Java_thread(), "must be a Java thread");
return ret;
}
}
bool JavaThread::is_lock_owned(address adr) const {
if (Thread::is_lock_owned(adr)) return true;
for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
if (chunk->contains(adr)) return true;
}
return false;
}
void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
chunk->set_next(monitor_chunks());
set_monitor_chunks(chunk);
}
void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
guarantee(monitor_chunks() != NULL, "must be non empty");
if (monitor_chunks() == chunk) {
set_monitor_chunks(chunk->next());
} else {
MonitorChunk* prev = monitor_chunks();
while (prev->next() != chunk) prev = prev->next();
prev->set_next(chunk->next());
}
}
// JVM support.
// Note: this function shouldn't block if it's called in
// _thread_in_native_trans state (such as from
// check_special_condition_for_native_trans()).
void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
if (has_last_Java_frame() && has_async_condition()) {
// If we are at a polling page safepoint (not a poll return)
// then we must defer async exception because live registers
// will be clobbered by the exception path. Poll return is
// ok because the call we a returning from already collides
// with exception handling registers and so there is no issue.
// (The exception handling path kills call result registers but
// this is ok since the exception kills the result anyway).
if (is_at_poll_safepoint()) {
// if the code we are returning to has deoptimized we must defer
// the exception otherwise live registers get clobbered on the
// exception path before deoptimization is able to retrieve them.
//
RegisterMap map(this, false);
frame caller_fr = last_frame().sender(&map);
assert(caller_fr.is_compiled_frame(), "what?");
if (caller_fr.is_deoptimized_frame()) {
log_info(exceptions)("deferred async exception at compiled safepoint");
return;
}
}
}
JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
if (condition == _no_async_condition) {
// Conditions have changed since has_special_runtime_exit_condition()
// was called:
// - if we were here only because of an external suspend request,
// then that was taken care of above (or cancelled) so we are done
// - if we were here because of another async request, then it has
// been cleared between the has_special_runtime_exit_condition()
// and now so again we are done
return;
}
// Check for pending async. exception
if (_pending_async_exception != NULL) {
// Only overwrite an already pending exception, if it is not a threadDeath.
if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
// We cannot call Exceptions::_throw(...) here because we cannot block
set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
LogTarget(Info, exceptions) lt;
if (lt.is_enabled()) {
ResourceMark rm;
LogStream ls(lt);
ls.print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", p2i(this));
if (has_last_Java_frame()) {
frame f = last_frame();
ls.print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", p2i(f.pc()), p2i(f.sp()));
}
ls.print_cr(" of type: %s", _pending_async_exception->klass()->external_name());
}
_pending_async_exception = NULL;
clear_has_async_exception();
}
}
if (check_unsafe_error &&
condition == _async_unsafe_access_error && !has_pending_exception()) {
condition = _no_async_condition; // done
switch (thread_state()) {
case _thread_in_vm: {
JavaThread* THREAD = this;
THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
}
case _thread_in_native: {
ThreadInVMfromNative tiv(this);
JavaThread* THREAD = this;
THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
}
case _thread_in_Java: {
ThreadInVMfromJava tiv(this);
JavaThread* THREAD = this;
THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
}
default:
ShouldNotReachHere();
}
}
assert(condition == _no_async_condition || has_pending_exception() ||
(!check_unsafe_error && condition == _async_unsafe_access_error),
"must have handled the async condition, if no exception");
}
void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
// Check for pending external suspend.
if (is_external_suspend_with_lock()) {
frame_anchor()->make_walkable(this);
java_suspend_self_with_safepoint_check();
}
// We might be here for reasons in addition to the self-suspend request
// so check for other async requests.
if (check_asyncs) {
check_and_handle_async_exceptions();
}
JFR_ONLY(SUSPEND_THREAD_CONDITIONAL(this);)
}
void JavaThread::send_thread_stop(oop java_throwable) {
assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
// Do not throw asynchronous exceptions against the compiler thread
// (the compiler thread should not be a Java thread -- fix in 1.4.2)
if (!can_call_java()) return;
{
// Actually throw the Throwable against the target Thread - however
// only if there is no thread death exception installed already.
if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
// If the topmost frame is a runtime stub, then we are calling into
// OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
// must deoptimize the caller before continuing, as the compiled exception handler table
// may not be valid
if (has_last_Java_frame()) {
frame f = last_frame();
if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
// BiasedLocking needs an updated RegisterMap for the revoke monitors pass
RegisterMap reg_map(this, UseBiasedLocking);
frame compiled_frame = f.sender(®_map);
if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
Deoptimization::deoptimize(this, compiled_frame, ®_map);
}
}
}
// Set async. pending exception in thread.
set_pending_async_exception(java_throwable);
if (log_is_enabled(Info, exceptions)) {
ResourceMark rm;
log_info(exceptions)("Pending Async. exception installed of type: %s",
InstanceKlass::cast(_pending_async_exception->klass())->external_name());
}
// for AbortVMOnException flag
Exceptions::debug_check_abort(_pending_async_exception->klass()->external_name());
}
}
// Interrupt thread so it will wake up from a potential wait()/sleep()/park()
java_lang_Thread::set_interrupted(threadObj(), true);
this->interrupt();
}
// External suspension mechanism.
//
// Tell the VM to suspend a thread when ever it knows that it does not hold on
// to any VM_locks and it is at a transition
// Self-suspension will happen on the transition out of the vm.
// Catch "this" coming in from JNIEnv pointers when the thread has been freed
//
// Guarantees on return:
// + Target thread will not execute any new bytecode (that's why we need to
// force a safepoint)
// + Target thread will not enter any new monitors
//
void JavaThread::java_suspend() {
ThreadsListHandle tlh;
if (!tlh.includes(this) || threadObj() == NULL || is_exiting()) {
return;
}
{ MutexLocker ml(SR_lock(), Mutex::_no_safepoint_check_flag);
if (!is_external_suspend()) {
// a racing resume has cancelled us; bail out now
return;
}
// suspend is done
uint32_t debug_bits = 0;
// Warning: is_ext_suspend_completed() may temporarily drop the
// SR_lock to allow the thread to reach a stable thread state if
// it is currently in a transient thread state.
if (is_ext_suspend_completed(false /* !called_by_wait */,
SuspendRetryDelay, &debug_bits)) {
return;
}
}
if (Thread::current() == this) {
// Safely self-suspend.
// If we don't do this explicitly it will implicitly happen
// before we transition back to Java, and on some other thread-state
// transition paths, but not as we exit a JVM TI SuspendThread call.
// As SuspendThread(current) must not return (until resumed) we must
// self-suspend here.
ThreadBlockInVM tbivm(this);
java_suspend_self();
} else {
VM_ThreadSuspend vm_suspend;
VMThread::execute(&vm_suspend);
}
}
// Part II of external suspension.
// A JavaThread self suspends when it detects a pending external suspend
// request. This is usually on transitions. It is also done in places
// where continuing to the next transition would surprise the caller,
// e.g., monitor entry.
//
// Returns the number of times that the thread self-suspended.
//
// Note: DO NOT call java_suspend_self() when you just want to block current
// thread. java_suspend_self() is the second stage of cooperative
// suspension for external suspend requests and should only be used
// to complete an external suspend request.
//
int JavaThread::java_suspend_self() {
assert(thread_state() == _thread_blocked, "wrong state for java_suspend_self()");
int ret = 0;
// we are in the process of exiting so don't suspend
if (is_exiting()) {
clear_external_suspend();
return ret;
}
assert(_anchor.walkable() ||
(is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
"must have walkable stack");
MonitorLocker ml(SR_lock(), Mutex::_no_safepoint_check_flag);
assert(!this->is_ext_suspended(),
"a thread trying to self-suspend should not already be suspended");
if (this->is_suspend_equivalent()) {
// If we are self-suspending as a result of the lifting of a
// suspend equivalent condition, then the suspend_equivalent
// flag is not cleared until we set the ext_suspended flag so
// that wait_for_ext_suspend_completion() returns consistent
// results.
this->clear_suspend_equivalent();
}
// A racing resume may have cancelled us before we grabbed SR_lock
// above. Or another external suspend request could be waiting for us
// by the time we return from SR_lock()->wait(). The thread
// that requested the suspension may already be trying to walk our
// stack and if we return now, we can change the stack out from under
// it. This would be a "bad thing (TM)" and cause the stack walker
// to crash. We stay self-suspended until there are no more pending
// external suspend requests.
while (is_external_suspend()) {
ret++;
this->set_ext_suspended();
// _ext_suspended flag is cleared by java_resume()
while (is_ext_suspended()) {
ml.wait();
}
}
return ret;
}
// Helper routine to set up the correct thread state before calling java_suspend_self.
// This is called when regular thread-state transition helpers can't be used because
// we can be in various states, in particular _thread_in_native_trans.
// Because this thread is external suspended the safepoint code will count it as at
// a safepoint, regardless of what its actual current thread-state is. But
// is_ext_suspend_completed() may be waiting to see a thread transition from
// _thread_in_native_trans to _thread_blocked. So we set the thread state directly
// to _thread_blocked. The problem with setting thread state directly is that a
// safepoint could happen just after java_suspend_self() returns after being resumed,
// and the VM thread will see the _thread_blocked state. So we must check for a safepoint
// after restoring the state to make sure we won't leave while a safepoint is in progress.
// However, not all initial-states are allowed when performing a safepoint check, as we
// should never be blocking at a safepoint whilst in those states. Of these 'bad' states
// only _thread_in_native is possible when executing this code (based on our two callers).
// A thread that is _thread_in_native is already safepoint-safe and so it doesn't matter
// whether the VMThread sees the _thread_blocked state, or the _thread_in_native state,
// and so we don't need the explicit safepoint check.
void JavaThread::java_suspend_self_with_safepoint_check() {
assert(this == Thread::current(), "invariant");
JavaThreadState state = thread_state();
set_thread_state(_thread_blocked);
java_suspend_self();
set_thread_state_fence(state);
// Since we are not using a regular thread-state transition helper here,
// we must manually emit the instruction barrier after leaving a safe state.
OrderAccess::cross_modify_fence();
if (state != _thread_in_native) {
SafepointMechanism::block_if_requested(this);
}
}
#ifdef ASSERT
// Verify the JavaThread has not yet been published in the Threads::list, and
// hence doesn't need protection from concurrent access at this stage.
void JavaThread::verify_not_published() {
// Cannot create a ThreadsListHandle here and check !tlh.includes(this)
// since an unpublished JavaThread doesn't participate in the
// Thread-SMR protocol for keeping a ThreadsList alive.
assert(!on_thread_list(), "JavaThread shouldn't have been published yet!");
}
#endif
// Slow path when the native==>VM/Java barriers detect a safepoint is in
// progress or when _suspend_flags is non-zero.
// Current thread needs to self-suspend if there is a suspend request and/or
// block if a safepoint is in progress.
// Async exception ISN'T checked.
// Note only the ThreadInVMfromNative transition can call this function
// directly and when thread state is _thread_in_native_trans
void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
if (thread->is_external_suspend()) {
thread->java_suspend_self_with_safepoint_check();
} else {
SafepointMechanism::block_if_requested(thread);
}
JFR_ONLY(SUSPEND_THREAD_CONDITIONAL(thread);)
}
// Slow path when the native==>VM/Java barriers detect a safepoint is in
// progress or when _suspend_flags is non-zero.
// Current thread needs to self-suspend if there is a suspend request and/or
// block if a safepoint is in progress.
// Also check for pending async exception (not including unsafe access error).
// Note only the native==>VM/Java barriers can call this function and when
// thread state is _thread_in_native_trans.
void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
check_safepoint_and_suspend_for_native_trans(thread);
if (thread->has_async_exception()) {
// We are in _thread_in_native_trans state, don't handle unsafe
// access error since that may block.
thread->check_and_handle_async_exceptions(false);
}
}
// This is a variant of the normal
// check_special_condition_for_native_trans with slightly different
// semantics for use by critical native wrappers. It does all the
// normal checks but also performs the transition back into
// thread_in_Java state. This is required so that critical natives
// can potentially block and perform a GC if they are the last thread
// exiting the GCLocker.
void JavaThread::check_special_condition_for_native_trans_and_transition(JavaThread *thread) {
check_special_condition_for_native_trans(thread);
// Finish the transition
thread->set_thread_state(_thread_in_Java);
if (thread->do_critical_native_unlock()) {
ThreadInVMfromJavaNoAsyncException tiv(thread);
GCLocker::unlock_critical(thread);
thread->clear_critical_native_unlock();
}
}
// We need to guarantee the Threads_lock here, since resumes are not
// allowed during safepoint synchronization
// Can only resume from an external suspension
void JavaThread::java_resume() {
assert_locked_or_safepoint(Threads_lock);
// Sanity check: thread is gone, has started exiting or the thread
// was not externally suspended.
ThreadsListHandle tlh;
if (!tlh.includes(this) || is_exiting() || !is_external_suspend()) {
return;
}
MutexLocker ml(SR_lock(), Mutex::_no_safepoint_check_flag);
clear_external_suspend();
if (is_ext_suspended()) {
clear_ext_suspended();
SR_lock()->notify_all();
}
}
size_t JavaThread::_stack_red_zone_size = 0;
size_t JavaThread::_stack_yellow_zone_size = 0;
size_t JavaThread::_stack_reserved_zone_size = 0;
size_t JavaThread::_stack_shadow_zone_size = 0;
void JavaThread::create_stack_guard_pages() {
if (!os::uses_stack_guard_pages() ||
_stack_guard_state != stack_guard_unused ||
(DisablePrimordialThreadGuardPages && os::is_primordial_thread())) {
log_info(os, thread)("Stack guard page creation for thread "
UINTX_FORMAT " disabled", os::current_thread_id());
return;
}
address low_addr = stack_end();
size_t len = stack_guard_zone_size();
assert(is_aligned(low_addr, os::vm_page_size()), "Stack base should be the start of a page");
assert(is_aligned(len, os::vm_page_size()), "Stack size should be a multiple of page size");
int must_commit = os::must_commit_stack_guard_pages();
// warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
if (must_commit && !os::create_stack_guard_pages((char *) low_addr, len)) {
log_warning(os, thread)("Attempt to allocate stack guard pages failed.");
return;
}
if (os::guard_memory((char *) low_addr, len)) {
_stack_guard_state = stack_guard_enabled;
} else {
log_warning(os, thread)("Attempt to protect stack guard pages failed ("
PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
if (os::uncommit_memory((char *) low_addr, len)) {
log_warning(os, thread)("Attempt to deallocate stack guard pages failed.");
}
return;
}
log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages activated: "
PTR_FORMAT "-" PTR_FORMAT ".",
os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
}
void JavaThread::remove_stack_guard_pages() {
assert(Thread::current() == this, "from different thread");
if (_stack_guard_state == stack_guard_unused) return;
address low_addr = stack_end();
size_t len = stack_guard_zone_size();
if (os::must_commit_stack_guard_pages()) {
if (os::remove_stack_guard_pages((char *) low_addr, len)) {
_stack_guard_state = stack_guard_unused;
} else {
log_warning(os, thread)("Attempt to deallocate stack guard pages failed ("
PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
return;
}
} else {
if (_stack_guard_state == stack_guard_unused) return;
if (os::unguard_memory((char *) low_addr, len)) {
_stack_guard_state = stack_guard_unused;
} else {
log_warning(os, thread)("Attempt to unprotect stack guard pages failed ("
PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
return;
}
}
log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages removed: "
PTR_FORMAT "-" PTR_FORMAT ".",
os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
}
void JavaThread::enable_stack_reserved_zone() {
assert(_stack_guard_state == stack_guard_reserved_disabled, "inconsistent state");
// The base notation is from the stack's point of view, growing downward.
// We need to adjust it to work correctly with guard_memory()
address base = stack_reserved_zone_base() - stack_reserved_zone_size();
guarantee(base < stack_base(),"Error calculating stack reserved zone");
guarantee(base < os::current_stack_pointer(),"Error calculating stack reserved zone");
if (os::guard_memory((char *) base, stack_reserved_zone_size())) {
_stack_guard_state = stack_guard_enabled;
} else {
warning("Attempt to guard stack reserved zone failed.");
}
enable_register_stack_guard();
}
void JavaThread::disable_stack_reserved_zone() {
assert(_stack_guard_state == stack_guard_enabled, "inconsistent state");
// Simply return if called for a thread that does not use guard pages.
if (_stack_guard_state != stack_guard_enabled) return;
// The base notation is from the stack's point of view, growing downward.
// We need to adjust it to work correctly with guard_memory()
address base = stack_reserved_zone_base() - stack_reserved_zone_size();
if (os::unguard_memory((char *)base, stack_reserved_zone_size())) {
_stack_guard_state = stack_guard_reserved_disabled;
} else {
warning("Attempt to unguard stack reserved zone failed.");
}
disable_register_stack_guard();
}
void JavaThread::enable_stack_yellow_reserved_zone() {
assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
assert(_stack_guard_state != stack_guard_enabled, "already enabled");
// The base notation is from the stacks point of view, growing downward.
// We need to adjust it to work correctly with guard_memory()
address base = stack_red_zone_base();
guarantee(base < stack_base(), "Error calculating stack yellow zone");
guarantee(base < os::current_stack_pointer(), "Error calculating stack yellow zone");
if (os::guard_memory((char *) base, stack_yellow_reserved_zone_size())) {
_stack_guard_state = stack_guard_enabled;
} else {
warning("Attempt to guard stack yellow zone failed.");
}
enable_register_stack_guard();
}
void JavaThread::disable_stack_yellow_reserved_zone() {
assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
assert(_stack_guard_state != stack_guard_yellow_reserved_disabled, "already disabled");
// Simply return if called for a thread that does not use guard pages.
if (_stack_guard_state == stack_guard_unused) return;
// The base notation is from the stacks point of view, growing downward.
// We need to adjust it to work correctly with guard_memory()
address base = stack_red_zone_base();
if (os::unguard_memory((char *)base, stack_yellow_reserved_zone_size())) {
_stack_guard_state = stack_guard_yellow_reserved_disabled;
} else {
warning("Attempt to unguard stack yellow zone failed.");
}
disable_register_stack_guard();
}
void JavaThread::enable_stack_red_zone() {
// The base notation is from the stacks point of view, growing downward.
// We need to adjust it to work correctly with guard_memory()
assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
address base = stack_red_zone_base() - stack_red_zone_size();
guarantee(base < stack_base(), "Error calculating stack red zone");
guarantee(base < os::current_stack_pointer(), "Error calculating stack red zone");
if (!os::guard_memory((char *) base, stack_red_zone_size())) {
warning("Attempt to guard stack red zone failed.");
}
}
void JavaThread::disable_stack_red_zone() {
// The base notation is from the stacks point of view, growing downward.
// We need to adjust it to work correctly with guard_memory()
assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
address base = stack_red_zone_base() - stack_red_zone_size();
if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
warning("Attempt to unguard stack red zone failed.");
}
}
void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
// ignore is there is no stack
if (!has_last_Java_frame()) return;
// traverse the stack frames. Starts from top frame.
for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
frame* fr = fst.current();
f(fr, fst.register_map());
}
}
#ifndef PRODUCT
// Deoptimization
// Function for testing deoptimization
void JavaThread::deoptimize() {
// BiasedLocking needs an updated RegisterMap for the revoke monitors pass
StackFrameStream fst(this, UseBiasedLocking);
bool deopt = false; // Dump stack only if a deopt actually happens.
bool only_at = strlen(DeoptimizeOnlyAt) > 0;
// Iterate over all frames in the thread and deoptimize
for (; !fst.is_done(); fst.next()) {
if (fst.current()->can_be_deoptimized()) {
if (only_at) {
// Deoptimize only at particular bcis. DeoptimizeOnlyAt
// consists of comma or carriage return separated numbers so
// search for the current bci in that string.
address pc = fst.current()->pc();
nmethod* nm = (nmethod*) fst.current()->cb();
ScopeDesc* sd = nm->scope_desc_at(pc);
char buffer[8];
jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
size_t len = strlen(buffer);
const char * found = strstr(DeoptimizeOnlyAt, buffer);
while (found != NULL) {
if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
(found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
// Check that the bci found is bracketed by terminators.
break;
}
found = strstr(found + 1, buffer);
}
if (!found) {
continue;
}
}
if (DebugDeoptimization && !deopt) {
deopt = true; // One-time only print before deopt
tty->print_cr("[BEFORE Deoptimization]");
trace_frames();
trace_stack();
}
Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
}
}
if (DebugDeoptimization && deopt) {
tty->print_cr("[AFTER Deoptimization]");
trace_frames();
}
}
// Make zombies
void JavaThread::make_zombies() {
for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
if (fst.current()->can_be_deoptimized()) {
// it is a Java nmethod
nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
nm->make_not_entrant();
}
}
}
#endif // PRODUCT
void JavaThread::deoptimize_marked_methods() {
if (!has_last_Java_frame()) return;
// BiasedLocking needs an updated RegisterMap for the revoke monitors pass
StackFrameStream fst(this, UseBiasedLocking);
for (; !fst.is_done(); fst.next()) {
if (fst.current()->should_be_deoptimized()) {
Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
}
}
}
// If the caller is a NamedThread, then remember, in the current scope,
// the given JavaThread in its _processed_thread field.
class RememberProcessedThread: public StackObj {
NamedThread* _cur_thr;
public:
RememberProcessedThread(JavaThread* jthr) {
Thread* thread = Thread::current();
if (thread->is_Named_thread()) {
_cur_thr = (NamedThread *)thread;
_cur_thr->set_processed_thread(jthr);
} else {
_cur_thr = NULL;
}
}
~RememberProcessedThread() {
if (_cur_thr) {
_cur_thr->set_processed_thread(NULL);
}
}
};
void JavaThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
// Verify that the deferred card marks have been flushed.
assert(deferred_card_mark().is_empty(), "Should be empty during GC");
// Traverse the GCHandles
Thread::oops_do(f, cf);
assert((!has_last_Java_frame() && java_call_counter() == 0) ||
(has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
if (has_last_Java_frame()) {
// Record JavaThread to GC thread
RememberProcessedThread rpt(this);
// traverse the registered growable array
if (_array_for_gc != NULL) {
for (int index = 0; index < _array_for_gc->length(); index++) {
f->do_oop(_array_for_gc->adr_at(index));
}
}
// Traverse the monitor chunks
for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
chunk->oops_do(f);
}
// Traverse the execution stack
for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
fst.current()->oops_do(f, cf, fst.register_map());
}
}
assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
// If we have deferred set_locals there might be oops waiting to be
// written
GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
if (list != NULL) {
for (int i = 0; i < list->length(); i++) {
list->at(i)->oops_do(f);
}
}
// Traverse instance variables at the end since the GC may be moving things
// around using this function
f->do_oop((oop*) &_threadObj);
f->do_oop((oop*) &_vm_result);
f->do_oop((oop*) &_exception_oop);
f->do_oop((oop*) &_pending_async_exception);
if (jvmti_thread_state() != NULL) {
jvmti_thread_state()->oops_do(f);
}
}
#ifdef ASSERT
void JavaThread::verify_states_for_handshake() {
// This checks that the thread has a correct frame state during a handshake.
assert((!has_last_Java_frame() && java_call_counter() == 0) ||
(has_last_Java_frame() && java_call_counter() > 0),
"unexpected frame info: has_last_frame=%d, java_call_counter=%d",
has_last_Java_frame(), java_call_counter());
}
#endif
void JavaThread::nmethods_do(CodeBlobClosure* cf) {
assert((!has_last_Java_frame() && java_call_counter() == 0) ||
(has_last_Java_frame() && java_call_counter() > 0),
"unexpected frame info: has_last_frame=%d, java_call_counter=%d",
has_last_Java_frame(), java_call_counter());
if (has_last_Java_frame()) {
// Traverse the execution stack
for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
fst.current()->nmethods_do(cf);
}
}
}
void JavaThread::metadata_do(MetadataClosure* f) {
if (has_last_Java_frame()) {
// Traverse the execution stack to call f() on the methods in the stack
for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
fst.current()->metadata_do(f);
}
} else if (is_Compiler_thread()) {
// need to walk ciMetadata in current compile tasks to keep alive.
CompilerThread* ct = (CompilerThread*)this;
if (ct->env() != NULL) {
ct->env()->metadata_do(f);
}
CompileTask* task = ct->task();
if (task != NULL) {
task->metadata_do(f);
}
}
}
// Printing
const char* _get_thread_state_name(JavaThreadState _thread_state) {
switch (_thread_state) {
case _thread_uninitialized: return "_thread_uninitialized";
case _thread_new: return "_thread_new";
case _thread_new_trans: return "_thread_new_trans";
case _thread_in_native: return "_thread_in_native";
case _thread_in_native_trans: return "_thread_in_native_trans";
case _thread_in_vm: return "_thread_in_vm";
case _thread_in_vm_trans: return "_thread_in_vm_trans";
case _thread_in_Java: return "_thread_in_Java";
case _thread_in_Java_trans: return "_thread_in_Java_trans";
case _thread_blocked: return "_thread_blocked";
case _thread_blocked_trans: return "_thread_blocked_trans";
default: return "unknown thread state";
}
}
#ifndef PRODUCT
void JavaThread::print_thread_state_on(outputStream *st) const {
st->print_cr(" JavaThread state: %s", _get_thread_state_name(_thread_state));
};
#endif // PRODUCT
// Called by Threads::print() for VM_PrintThreads operation
void JavaThread::print_on(outputStream *st, bool print_extended_info) const {
st->print_raw("\"");
st->print_raw(get_thread_name());
st->print_raw("\" ");
oop thread_oop = threadObj();
if (thread_oop != NULL) {
st->print("#" INT64_FORMAT " ", (int64_t)java_lang_Thread::thread_id(thread_oop));
if (java_lang_Thread::is_daemon(thread_oop)) st->print("daemon ");
st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
}
Thread::print_on(st, print_extended_info);
// print guess for valid stack memory region (assume 4K pages); helps lock debugging
st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
if (thread_oop != NULL) {
st->print_cr(" java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
}
#ifndef PRODUCT
_safepoint_state->print_on(st);
#endif // PRODUCT
if (is_Compiler_thread()) {
CompileTask *task = ((CompilerThread*)this)->task();
if (task != NULL) {
st->print(" Compiling: ");
task->print(st, NULL, true, false);
} else {
st->print(" No compile task");
}
st->cr();
}
}
void JavaThread::print() const { print_on(tty); }
void JavaThread::print_name_on_error(outputStream* st, char *buf, int buflen) const {
st->print("%s", get_thread_name_string(buf, buflen));
}
// Called by fatal error handler. The difference between this and
// JavaThread::print() is that we can't grab lock or allocate memory.
void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
st->print("JavaThread \"%s\"", get_thread_name_string(buf, buflen));
oop thread_obj = threadObj();
if (thread_obj != NULL) {
if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
}
st->print(" [");
st->print("%s", _get_thread_state_name(_thread_state));
if (osthread()) {
st->print(", id=%d", osthread()->thread_id());
}
st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
p2i(stack_end()), p2i(stack_base()));
st->print("]");
ThreadsSMRSupport::print_info_on(this, st);
return;
}
// Verification
static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
void JavaThread::verify() {
// Verify oops in the thread.
oops_do(&VerifyOopClosure::verify_oop, NULL);
// Verify the stack frames.
frames_do(frame_verify);
}
// CR 6300358 (sub-CR 2137150)
// Most callers of this method assume that it can't return NULL but a
// thread may not have a name whilst it is in the process of attaching to
// the VM - see CR 6412693, and there are places where a JavaThread can be
// seen prior to having it's threadObj set (eg JNI attaching threads and
// if vm exit occurs during initialization). These cases can all be accounted
// for such that this method never returns NULL.
const char* JavaThread::get_thread_name() const {
#ifdef ASSERT
// early safepoints can hit while current thread does not yet have TLS
if (!SafepointSynchronize::is_at_safepoint()) {
Thread *cur = Thread::current();
if (!(cur->is_Java_thread() && cur == this)) {
// Current JavaThreads are allowed to get their own name without
// the Threads_lock.
assert_locked_or_safepoint(Threads_lock);
}
}
#endif // ASSERT
return get_thread_name_string();
}
// Returns a non-NULL representation of this thread's name, or a suitable
// descriptive string if there is no set name
const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
const char* name_str;
oop thread_obj = threadObj();
if (thread_obj != NULL) {
oop name = java_lang_Thread::name(thread_obj);
if (name != NULL) {
if (buf == NULL) {
name_str = java_lang_String::as_utf8_string(name);
} else {
name_str = java_lang_String::as_utf8_string(name, buf, buflen);
}
} else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
name_str = "<no-name - thread is attaching>";
} else {
name_str = Thread::name();
}
} else {
name_str = Thread::name();
}
assert(name_str != NULL, "unexpected NULL thread name");
return name_str;
}
void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
assert(NoPriority <= prio && prio <= MaxPriority, "sanity check");
// Link Java Thread object <-> C++ Thread
// Get the C++ thread object (an oop) from the JNI handle (a jthread)
// and put it into a new Handle. The Handle "thread_oop" can then
// be used to pass the C++ thread object to other methods.
// Set the Java level thread object (jthread) field of the
// new thread (a JavaThread *) to C++ thread object using the
// "thread_oop" handle.
// Set the thread field (a JavaThread *) of the
// oop representing the java_lang_Thread to the new thread (a JavaThread *).
Handle thread_oop(Thread::current(),
JNIHandles::resolve_non_null(jni_thread));
assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
"must be initialized");
set_threadObj(thread_oop());
java_lang_Thread::set_thread(thread_oop(), this);
if (prio == NoPriority) {
prio = java_lang_Thread::priority(thread_oop());
assert(prio != NoPriority, "A valid priority should be present");
}
// Push the Java priority down to the native thread; needs Threads_lock
Thread::set_priority(this, prio);
// Add the new thread to the Threads list and set it in motion.
// We must have threads lock in order to call Threads::add.
// It is crucial that we do not block before the thread is
// added to the Threads list for if a GC happens, then the java_thread oop
// will not be visited by GC.
Threads::add(this);
}
oop JavaThread::current_park_blocker() {
// Support for JSR-166 locks
oop thread_oop = threadObj();
if (thread_oop != NULL) {
return java_lang_Thread::park_blocker(thread_oop);
}
return NULL;
}
void JavaThread::print_stack_on(outputStream* st) {
if (!has_last_Java_frame()) return;
ResourceMark rm;
HandleMark hm;
RegisterMap reg_map(this);
vframe* start_vf = last_java_vframe(®_map);
int count = 0;
for (vframe* f = start_vf; f != NULL; f = f->sender()) {
if (f->is_java_frame()) {
javaVFrame* jvf = javaVFrame::cast(f);
java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
// Print out lock information
if (JavaMonitorsInStackTrace) {
jvf->print_lock_info_on(st, count);
}
} else {
// Ignore non-Java frames
}
// Bail-out case for too deep stacks if MaxJavaStackTraceDepth > 0
count++;
if (MaxJavaStackTraceDepth > 0 && MaxJavaStackTraceDepth == count) return;
}
}
// JVMTI PopFrame support
void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
if (in_bytes(size_in_bytes) != 0) {
_popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
_popframe_preserved_args_size = in_bytes(size_in_bytes);
Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
}
}
void* JavaThread::popframe_preserved_args() {
return _popframe_preserved_args;
}
ByteSize JavaThread::popframe_preserved_args_size() {
return in_ByteSize(_popframe_preserved_args_size);
}
WordSize JavaThread::popframe_preserved_args_size_in_words() {
int sz = in_bytes(popframe_preserved_args_size());
assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
return in_WordSize(sz / wordSize);
}
void JavaThread::popframe_free_preserved_args() {
assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
FREE_C_HEAP_ARRAY(char, (char*)_popframe_preserved_args);
_popframe_preserved_args = NULL;
_popframe_preserved_args_size = 0;
}
#ifndef PRODUCT
void JavaThread::trace_frames() {
tty->print_cr("[Describe stack]");
int frame_no = 1;
for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
tty->print(" %d. ", frame_no++);
fst.current()->print_value_on(tty, this);
tty->cr();
}
}
class PrintAndVerifyOopClosure: public OopClosure {
protected:
template <class T> inline void do_oop_work(T* p) {
oop obj = RawAccess<>::oop_load(p);
if (obj == NULL) return;
tty->print(INTPTR_FORMAT ": ", p2i(p));
if (oopDesc::is_oop_or_null(obj)) {
if (obj->is_objArray()) {
tty->print_cr("valid objArray: " INTPTR_FORMAT, p2i(obj));
} else {
obj->print();
}
} else {
tty->print_cr("invalid oop: " INTPTR_FORMAT, p2i(obj));
}
tty->cr();
}
public:
virtual void do_oop(oop* p) { do_oop_work(p); }
virtual void do_oop(narrowOop* p) { do_oop_work(p); }
};
#ifdef ASSERT
// Print or validate the layout of stack frames
void JavaThread::print_frame_layout(int depth, bool validate_only) {
ResourceMark rm;
PRESERVE_EXCEPTION_MARK;
FrameValues values;
int frame_no = 0;
for (StackFrameStream fst(this, false); !fst.is_done(); fst.next()) {
fst.current()->describe(values, ++frame_no);
if (depth == frame_no) break;
}
if (validate_only) {
values.validate();
} else {
tty->print_cr("[Describe stack layout]");
values.print(this);
}
}
#endif
void JavaThread::trace_stack_from(vframe* start_vf) {
ResourceMark rm;
int vframe_no = 1;
for (vframe* f = start_vf; f; f = f->sender()) {
if (f->is_java_frame()) {
javaVFrame::cast(f)->print_activation(vframe_no++);
} else {
f->print();
}
if (vframe_no > StackPrintLimit) {
tty->print_cr("...<more frames>...");
return;
}
}
}
void JavaThread::trace_stack() {
if (!has_last_Java_frame()) return;
ResourceMark rm;
HandleMark hm;
RegisterMap reg_map(this);
trace_stack_from(last_java_vframe(®_map));
}
#endif // PRODUCT
javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
assert(reg_map != NULL, "a map must be given");
frame f = last_frame();
for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender()) {
if (vf->is_java_frame()) return javaVFrame::cast(vf);
}
return NULL;
}
Klass* JavaThread::security_get_caller_class(int depth) {
vframeStream vfst(this);
vfst.security_get_caller_frame(depth);
if (!vfst.at_end()) {
return vfst.method()->method_holder();
}
return NULL;
}
// java.lang.Thread.sleep support
// Returns true if sleep time elapsed as expected, and false
// if the thread was interrupted.
bool JavaThread::sleep(jlong millis) {
assert(this == Thread::current(), "thread consistency check");
ParkEvent * const slp = this->_SleepEvent;
// Because there can be races with thread interruption sending an unpark()
// to the event, we explicitly reset it here to avoid an immediate return.
// The actual interrupt state will be checked before we park().
slp->reset();
// Thread interruption establishes a happens-before ordering in the
// Java Memory Model, so we need to ensure we synchronize with the
// interrupt state.
OrderAccess::fence();
jlong prevtime = os::javaTimeNanos();
for (;;) {
// interruption has precedence over timing out
if (this->is_interrupted(true)) {
return false;
}
if (millis <= 0) {
return true;
}
{
ThreadBlockInVM tbivm(this);
OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
this->set_suspend_equivalent();
// cleared by handle_special_suspend_equivalent_condition() or
// java_suspend_self() via check_and_wait_while_suspended()
slp->park(millis);
// were we externally suspended while we were waiting?
this->check_and_wait_while_suspended();
}
// Update elapsed time tracking
jlong newtime = os::javaTimeNanos();
if (newtime - prevtime < 0) {
// time moving backwards, should only happen if no monotonic clock
// not a guarantee() because JVM should not abort on kernel/glibc bugs
assert(!os::supports_monotonic_clock(),
"unexpected time moving backwards detected in JavaThread::sleep()");
} else {
millis -= (newtime - prevtime) / NANOSECS_PER_MILLISEC;
}
prevtime = newtime;
}
}
static void compiler_thread_entry(JavaThread* thread, TRAPS) {
assert(thread->is_Compiler_thread(), "must be compiler thread");
CompileBroker::compiler_thread_loop();
}
static void sweeper_thread_entry(JavaThread* thread, TRAPS) {
NMethodSweeper::sweeper_loop();
}
// Create a CompilerThread
CompilerThread::CompilerThread(CompileQueue* queue,
CompilerCounters* counters)
: JavaThread(&compiler_thread_entry) {
_env = NULL;
_log = NULL;
_task = NULL;
_queue = queue;
_counters = counters;
_buffer_blob = NULL;
_compiler = NULL;
// Compiler uses resource area for compilation, let's bias it to mtCompiler
resource_area()->bias_to(mtCompiler);
#ifndef PRODUCT
_ideal_graph_printer = NULL;
#endif
}
CompilerThread::~CompilerThread() {
// Delete objects which were allocated on heap.
delete _counters;
}
bool CompilerThread::can_call_java() const {
return _compiler != NULL && _compiler->is_jvmci();
}
// Create sweeper thread
CodeCacheSweeperThread::CodeCacheSweeperThread()
: JavaThread(&sweeper_thread_entry) {
_scanned_compiled_method = NULL;
}
void CodeCacheSweeperThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
JavaThread::oops_do(f, cf);
if (_scanned_compiled_method != NULL && cf != NULL) {
// Safepoints can occur when the sweeper is scanning an nmethod so
// process it here to make sure it isn't unloaded in the middle of
// a scan.
cf->do_code_blob(_scanned_compiled_method);
}
}
void CodeCacheSweeperThread::nmethods_do(CodeBlobClosure* cf) {
JavaThread::nmethods_do(cf);
if (_scanned_compiled_method != NULL && cf != NULL) {
// Safepoints can occur when the sweeper is scanning an nmethod so
// process it here to make sure it isn't unloaded in the middle of
// a scan.
cf->do_code_blob(_scanned_compiled_method);
}
}
// ======= Threads ========
// The Threads class links together all active threads, and provides
// operations over all threads. It is protected by the Threads_lock,
// which is also used in other global contexts like safepointing.
// ThreadsListHandles are used to safely perform operations on one
// or more threads without the risk of the thread exiting during the
// operation.
//
// Note: The Threads_lock is currently more widely used than we
// would like. We are actively migrating Threads_lock uses to other
// mechanisms in order to reduce Threads_lock contention.
int Threads::_number_of_threads = 0;
int Threads::_number_of_non_daemon_threads = 0;
int Threads::_return_code = 0;
uintx Threads::_thread_claim_token = 1; // Never zero.
size_t JavaThread::_stack_size_at_create = 0;
#ifdef ASSERT
bool Threads::_vm_complete = false;
#endif
static inline void *prefetch_and_load_ptr(void **addr, intx prefetch_interval) {
Prefetch::read((void*)addr, prefetch_interval);
return *addr;
}
// Possibly the ugliest for loop the world has seen. C++ does not allow
// multiple types in the declaration section of the for loop. In this case
// we are only dealing with pointers and hence can cast them. It looks ugly
// but macros are ugly and therefore it's fine to make things absurdly ugly.
#define DO_JAVA_THREADS(LIST, X) \
for (JavaThread *MACRO_scan_interval = (JavaThread*)(uintptr_t)PrefetchScanIntervalInBytes, \
*MACRO_list = (JavaThread*)(LIST), \
**MACRO_end = ((JavaThread**)((ThreadsList*)MACRO_list)->threads()) + ((ThreadsList*)MACRO_list)->length(), \
**MACRO_current_p = (JavaThread**)((ThreadsList*)MACRO_list)->threads(), \
*X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval); \
MACRO_current_p != MACRO_end; \
MACRO_current_p++, \
X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval))
// All JavaThreads
#define ALL_JAVA_THREADS(X) DO_JAVA_THREADS(ThreadsSMRSupport::get_java_thread_list(), X)
// All NonJavaThreads (i.e., every non-JavaThread in the system).
void Threads::non_java_threads_do(ThreadClosure* tc) {
NoSafepointVerifier nsv;
for (NonJavaThread::Iterator njti; !njti.end(); njti.step()) {
tc->do_thread(njti.current());
}
}
// All JavaThreads
void Threads::java_threads_do(ThreadClosure* tc) {
assert_locked_or_safepoint(Threads_lock);
// ALL_JAVA_THREADS iterates through all JavaThreads.
ALL_JAVA_THREADS(p) {
tc->do_thread(p);
}
}
void Threads::java_threads_and_vm_thread_do(ThreadClosure* tc) {
assert_locked_or_safepoint(Threads_lock);
java_threads_do(tc);
tc->do_thread(VMThread::vm_thread());
}
// All JavaThreads + all non-JavaThreads (i.e., every thread in the system).
void Threads::threads_do(ThreadClosure* tc) {
assert_locked_or_safepoint(Threads_lock);
java_threads_do(tc);
non_java_threads_do(tc);
}
void Threads::possibly_parallel_threads_do(bool is_par, ThreadClosure* tc) {
uintx claim_token = Threads::thread_claim_token();
ALL_JAVA_THREADS(p) {
if (p->claim_threads_do(is_par, claim_token)) {
tc->do_thread(p);
}
}
VMThread* vmt = VMThread::vm_thread();
if (vmt->claim_threads_do(is_par, claim_token)) {
tc->do_thread(vmt);
}
}
// The system initialization in the library has three phases.
//
// Phase 1: java.lang.System class initialization
// java.lang.System is a primordial class loaded and initialized
// by the VM early during startup. java.lang.System.<clinit>
// only does registerNatives and keeps the rest of the class
// initialization work later until thread initialization completes.
//
// System.initPhase1 initializes the system properties, the static
// fields in, out, and err. Set up java signal handlers, OS-specific
// system settings, and thread group of the main thread.
static void call_initPhase1(TRAPS) {
Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
JavaValue result(T_VOID);
JavaCalls::call_static(&result, klass, vmSymbols::initPhase1_name(),
vmSymbols::void_method_signature(), CHECK);
}
// Phase 2. Module system initialization
// This will initialize the module system. Only java.base classes
// can be loaded until phase 2 completes.
//
// Call System.initPhase2 after the compiler initialization and jsr292
// classes get initialized because module initialization runs a lot of java
// code, that for performance reasons, should be compiled. Also, this will
// enable the startup code to use lambda and other language features in this
// phase and onward.
//
// After phase 2, The VM will begin search classes from -Xbootclasspath/a.
static void call_initPhase2(TRAPS) {
TraceTime timer("Initialize module system", TRACETIME_LOG(Info, startuptime));
Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
JavaValue result(T_INT);
JavaCallArguments args;
args.push_int(DisplayVMOutputToStderr);
args.push_int(log_is_enabled(Debug, init)); // print stack trace if exception thrown
JavaCalls::call_static(&result, klass, vmSymbols::initPhase2_name(),
vmSymbols::boolean_boolean_int_signature(), &args, CHECK);
if (result.get_jint() != JNI_OK) {
vm_exit_during_initialization(); // no message or exception
}
universe_post_module_init();
}
// Phase 3. final setup - set security manager, system class loader and TCCL
//
// This will instantiate and set the security manager, set the system class
// loader as well as the thread context class loader. The security manager
// and system class loader may be a custom class loaded from -Xbootclasspath/a,
// other modules or the application's classpath.
static void call_initPhase3(TRAPS) {
Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
JavaValue result(T_VOID);
JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(),
vmSymbols::void_method_signature(), CHECK);
}
void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) {
TraceTime timer("Initialize java.lang classes", TRACETIME_LOG(Info, startuptime));
if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
create_vm_init_libraries();
}
initialize_class(vmSymbols::java_lang_String(), CHECK);
// Inject CompactStrings value after the static initializers for String ran.
java_lang_String::set_compact_strings(CompactStrings);
// Initialize java_lang.System (needed before creating the thread)
initialize_class(vmSymbols::java_lang_System(), CHECK);
// The VM creates & returns objects of this class. Make sure it's initialized.
initialize_class(vmSymbols::java_lang_Class(), CHECK);
initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK);
Handle thread_group = create_initial_thread_group(CHECK);
Universe::set_main_thread_group(thread_group());
initialize_class(vmSymbols::java_lang_Thread(), CHECK);
oop thread_object = create_initial_thread(thread_group, main_thread, CHECK);
main_thread->set_threadObj(thread_object);
// Set thread status to running since main thread has
// been started and running.
java_lang_Thread::set_thread_status(thread_object,
java_lang_Thread::RUNNABLE);
// The VM creates objects of this class.
initialize_class(vmSymbols::java_lang_Module(), CHECK);
#ifdef ASSERT
InstanceKlass *k = SystemDictionary::UnsafeConstants_klass();
assert(k->is_not_initialized(), "UnsafeConstants should not already be initialized");
#endif
// initialize the hardware-specific constants needed by Unsafe
initialize_class(vmSymbols::jdk_internal_misc_UnsafeConstants(), CHECK);
jdk_internal_misc_UnsafeConstants::set_unsafe_constants();
// The VM preresolves methods to these classes. Make sure that they get initialized
initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK);
initialize_class(vmSymbols::java_lang_ref_Finalizer(), CHECK);
// Phase 1 of the system initialization in the library, java.lang.System class initialization
call_initPhase1(CHECK);
// get the Java runtime name, version, and vendor info after java.lang.System is initialized
JDK_Version::set_runtime_name(get_java_runtime_name(THREAD));
JDK_Version::set_runtime_version(get_java_runtime_version(THREAD));
JDK_Version::set_runtime_vendor_version(get_java_runtime_vendor_version(THREAD));
JDK_Version::set_runtime_vendor_vm_bug_url(get_java_runtime_vendor_vm_bug_url(THREAD));
// an instance of OutOfMemory exception has been allocated earlier
initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK);
initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK);
initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK);
initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK);
initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK);
initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK);
initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK);
initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK);
// Eager box cache initialization only if AOT is on and any library is loaded.
AOTLoader::initialize_box_caches(CHECK);
}
void Threads::initialize_jsr292_core_classes(TRAPS) {
TraceTime timer("Initialize java.lang.invoke classes", TRACETIME_LOG(Info, startuptime));
initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK);
initialize_class(vmSymbols::java_lang_invoke_ResolvedMethodName(), CHECK);
initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK);
initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK);
}
jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
extern void JDK_Version_init();
// Preinitialize version info.
VM_Version::early_initialize();
// Check version
if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
// Initialize library-based TLS
ThreadLocalStorage::init();
// Initialize the output stream module
ostream_init();
// Process java launcher properties.
Arguments::process_sun_java_launcher_properties(args);
// Initialize the os module
os::init();
// Record VM creation timing statistics
TraceVmCreationTime create_vm_timer;
create_vm_timer.start();
// Initialize system properties.
Arguments::init_system_properties();
// So that JDK version can be used as a discriminator when parsing arguments
JDK_Version_init();
// Update/Initialize System properties after JDK version number is known
Arguments::init_version_specific_system_properties();
// Make sure to initialize log configuration *before* parsing arguments
LogConfiguration::initialize(create_vm_timer.begin_time());
// Parse arguments
// Note: this internally calls os::init_container_support()
jint parse_result = Arguments::parse(args);
if (parse_result != JNI_OK) return parse_result;
os::init_before_ergo();
jint ergo_result = Arguments::apply_ergo();
if (ergo_result != JNI_OK) return ergo_result;
// Final check of all ranges after ergonomics which may change values.
if (!JVMFlagRangeList::check_ranges()) {
return JNI_EINVAL;
}
// Final check of all 'AfterErgo' constraints after ergonomics which may change values.
bool constraint_result = JVMFlagConstraintList::check_constraints(JVMFlagConstraint::AfterErgo);
if (!constraint_result) {
return JNI_EINVAL;
}
JVMFlagWriteableList::mark_startup();
if (PauseAtStartup) {
os::pause();
}
HOTSPOT_VM_INIT_BEGIN();
// Timing (must come after argument parsing)
TraceTime timer("Create VM", TRACETIME_LOG(Info, startuptime));
// Initialize the os module after parsing the args
jint os_init_2_result = os::init_2();
if (os_init_2_result != JNI_OK) return os_init_2_result;
#ifdef CAN_SHOW_REGISTERS_ON_ASSERT
// Initialize assert poison page mechanism.
if (ShowRegistersOnAssert) {
initialize_assert_poison();
}
#endif // CAN_SHOW_REGISTERS_ON_ASSERT
SafepointMechanism::initialize();
jint adjust_after_os_result = Arguments::adjust_after_os();
if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
// Initialize output stream logging
ostream_init_log();
// Convert -Xrun to -agentlib: if there is no JVM_OnLoad
// Must be before create_vm_init_agents()
if (Arguments::init_libraries_at_startup()) {
convert_vm_init_libraries_to_agents();
}
// Launch -agentlib/-agentpath and converted -Xrun agents
if (Arguments::init_agents_at_startup()) {
create_vm_init_agents();
}
// Initialize Threads state
_number_of_threads = 0;
_number_of_non_daemon_threads = 0;
// Initialize global data structures and create system classes in heap
vm_init_globals();
#if INCLUDE_JVMCI
if (JVMCICounterSize > 0) {
JavaThread::_jvmci_old_thread_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtJVMCI);
memset(JavaThread::_jvmci_old_thread_counters, 0, sizeof(jlong) * JVMCICounterSize);
} else {
JavaThread::_jvmci_old_thread_counters = NULL;
}
#endif // INCLUDE_JVMCI
// Attach the main thread to this os thread
JavaThread* main_thread = new JavaThread();
main_thread->set_thread_state(_thread_in_vm);
main_thread->initialize_thread_current();
// must do this before set_active_handles
main_thread->record_stack_base_and_size();
main_thread->register_thread_stack_with_NMT();
main_thread->set_active_handles(JNIHandleBlock::allocate_block());
if (!main_thread->set_as_starting_thread()) {
vm_shutdown_during_initialization(
"Failed necessary internal allocation. Out of swap space");
main_thread->smr_delete();
*canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
return JNI_ENOMEM;
}
// Enable guard page *after* os::create_main_thread(), otherwise it would
// crash Linux VM, see notes in os_linux.cpp.
main_thread->create_stack_guard_pages();
// Initialize Java-Level synchronization subsystem
ObjectMonitor::Initialize();
// Initialize global modules
jint status = init_globals();
if (status != JNI_OK) {
main_thread->smr_delete();
*canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
return status;
}
JFR_ONLY(Jfr::on_create_vm_1();)
// Should be done after the heap is fully created
main_thread->cache_global_variables();
HandleMark hm;
{ MutexLocker mu(Threads_lock);
Threads::add(main_thread);
}
// Any JVMTI raw monitors entered in onload will transition into
// real raw monitor. VM is setup enough here for raw monitor enter.
JvmtiExport::transition_pending_onload_raw_monitors();
// Create the VMThread
{ TraceTime timer("Start VMThread", TRACETIME_LOG(Info, startuptime));
VMThread::create();
Thread* vmthread = VMThread::vm_thread();
if (!os::create_thread(vmthread, os::vm_thread)) {
vm_exit_during_initialization("Cannot create VM thread. "
"Out of system resources.");
}
// Wait for the VM thread to become ready, and VMThread::run to initialize
// Monitors can have spurious returns, must always check another state flag
{
MonitorLocker ml(Notify_lock);
os::start_thread(vmthread);
while (vmthread->active_handles() == NULL) {
ml.wait();
}
}
}
assert(Universe::is_fully_initialized(), "not initialized");
if (VerifyDuringStartup) {
// Make sure we're starting with a clean slate.
VM_Verify verify_op;
VMThread::execute(&verify_op);
}
// We need this to update the java.vm.info property in case any flags used
// to initially define it have been changed. This is needed for both CDS and
// AOT, since UseSharedSpaces and UseAOT may be changed after java.vm.info
// is initially computed. See Abstract_VM_Version::vm_info_string().
// This update must happen before we initialize the java classes, but
// after any initialization logic that might modify the flags.
Arguments::update_vm_info_property(VM_Version::vm_info_string());
Thread* THREAD = Thread::current();
// Always call even when there are not JVMTI environments yet, since environments
// may be attached late and JVMTI must track phases of VM execution
JvmtiExport::enter_early_start_phase();
// Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
JvmtiExport::post_early_vm_start();
initialize_java_lang_classes(main_thread, CHECK_JNI_ERR);
quicken_jni_functions();
// No more stub generation allowed after that point.
StubCodeDesc::freeze();
// Set flag that basic initialization has completed. Used by exceptions and various
// debug stuff, that does not work until all basic classes have been initialized.
set_init_completed();
LogConfiguration::post_initialize();
Metaspace::post_initialize();
HOTSPOT_VM_INIT_END();
// record VM initialization completion time
#if INCLUDE_MANAGEMENT
Management::record_vm_init_completed();
#endif // INCLUDE_MANAGEMENT
// Signal Dispatcher needs to be started before VMInit event is posted
os::initialize_jdk_signal_support(CHECK_JNI_ERR);
// Start Attach Listener if +StartAttachListener or it can't be started lazily
if (!DisableAttachMechanism) {
AttachListener::vm_start();
if (StartAttachListener || AttachListener::init_at_startup()) {
AttachListener::init();
}
}
// Launch -Xrun agents
// Must be done in the JVMTI live phase so that for backward compatibility the JDWP
// back-end can launch with -Xdebug -Xrunjdwp.
if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
create_vm_init_libraries();
}
if (CleanChunkPoolAsync) {
Chunk::start_chunk_pool_cleaner_task();
}
// initialize compiler(s)
#if defined(COMPILER1) || COMPILER2_OR_JVMCI
#if INCLUDE_JVMCI
bool force_JVMCI_intialization = false;
if (EnableJVMCI) {
// Initialize JVMCI eagerly when it is explicitly requested.
// Or when JVMCILibDumpJNIConfig or JVMCIPrintProperties is enabled.
force_JVMCI_intialization = EagerJVMCI || JVMCIPrintProperties || JVMCILibDumpJNIConfig;
if (!force_JVMCI_intialization) {
// 8145270: Force initialization of JVMCI runtime otherwise requests for blocking
// compilations via JVMCI will not actually block until JVMCI is initialized.
force_JVMCI_intialization = UseJVMCICompiler && (!UseInterpreter || !BackgroundCompilation);
}
}
#endif
CompileBroker::compilation_init_phase1(CHECK_JNI_ERR);
// Postpone completion of compiler initialization to after JVMCI
// is initialized to avoid timeouts of blocking compilations.
if (JVMCI_ONLY(!force_JVMCI_intialization) NOT_JVMCI(true)) {
CompileBroker::compilation_init_phase2();
}
#endif
// Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
// It is done after compilers are initialized, because otherwise compilations of
// signature polymorphic MH intrinsics can be missed
// (see SystemDictionary::find_method_handle_intrinsic).
initialize_jsr292_core_classes(CHECK_JNI_ERR);
// This will initialize the module system. Only java.base classes can be
// loaded until phase 2 completes
call_initPhase2(CHECK_JNI_ERR);
JFR_ONLY(Jfr::on_create_vm_2();)
// Always call even when there are not JVMTI environments yet, since environments
// may be attached late and JVMTI must track phases of VM execution
JvmtiExport::enter_start_phase();
// Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
JvmtiExport::post_vm_start();
// Final system initialization including security manager and system class loader
call_initPhase3(CHECK_JNI_ERR);
// cache the system and platform class loaders
SystemDictionary::compute_java_loaders(CHECK_JNI_ERR);
#if INCLUDE_CDS
// capture the module path info from the ModuleEntryTable
ClassLoader::initialize_module_path(THREAD);
#endif
#if INCLUDE_JVMCI
if (force_JVMCI_intialization) {
JVMCI::initialize_compiler(CHECK_JNI_ERR);
CompileBroker::compilation_init_phase2();
}
#endif
// Always call even when there are not JVMTI environments yet, since environments
// may be attached late and JVMTI must track phases of VM execution
JvmtiExport::enter_live_phase();
// Make perfmemory accessible
PerfMemory::set_accessible(true);
// Notify JVMTI agents that VM initialization is complete - nop if no agents.
JvmtiExport::post_vm_initialized();
JFR_ONLY(Jfr::on_create_vm_3();)
#if INCLUDE_MANAGEMENT
Management::initialize(THREAD);
if (HAS_PENDING_EXCEPTION) {
// management agent fails to start possibly due to
// configuration problem and is responsible for printing
// stack trace if appropriate. Simply exit VM.
vm_exit(1);
}
#endif // INCLUDE_MANAGEMENT
if (MemProfiling) MemProfiler::engage();
StatSampler::engage();
if (CheckJNICalls) JniPeriodicChecker::engage();
BiasedLocking::init();
#if INCLUDE_RTM_OPT
RTMLockingCounters::init();
#endif
call_postVMInitHook(THREAD);
// The Java side of PostVMInitHook.run must deal with all
// exceptions and provide means of diagnosis.
if (HAS_PENDING_EXCEPTION) {
CLEAR_PENDING_EXCEPTION;
}
{
MutexLocker ml(PeriodicTask_lock);
// Make sure the WatcherThread can be started by WatcherThread::start()
// or by dynamic enrollment.
WatcherThread::make_startable();
// Start up the WatcherThread if there are any periodic tasks
// NOTE: All PeriodicTasks should be registered by now. If they
// aren't, late joiners might appear to start slowly (we might
// take a while to process their first tick).
if (PeriodicTask::num_tasks() > 0) {
WatcherThread::start();
}
}
create_vm_timer.end();
#ifdef ASSERT
_vm_complete = true;
#endif
if (DumpSharedSpaces) {
MetaspaceShared::preload_and_dump(CHECK_JNI_ERR);
ShouldNotReachHere();
}
return JNI_OK;
}
// type for the Agent_OnLoad and JVM_OnLoad entry points
extern "C" {
typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
}
// Find a command line agent library and return its entry point for
// -agentlib: -agentpath: -Xrun
// num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
static OnLoadEntry_t lookup_on_load(AgentLibrary* agent,
const char *on_load_symbols[],
size_t num_symbol_entries) {
OnLoadEntry_t on_load_entry = NULL;
void *library = NULL;
if (!agent->valid()) {
char buffer[JVM_MAXPATHLEN];
char ebuf[1024] = "";
const char *name = agent->name();
const char *msg = "Could not find agent library ";
// First check to see if agent is statically linked into executable
if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
library = agent->os_lib();
} else if (agent->is_absolute_path()) {
library = os::dll_load(name, ebuf, sizeof ebuf);
if (library == NULL) {
const char *sub_msg = " in absolute path, with error: ";
size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
// If we can't find the agent, exit.
vm_exit_during_initialization(buf, NULL);
FREE_C_HEAP_ARRAY(char, buf);
}
} else {
// Try to load the agent from the standard dll directory
if (os::dll_locate_lib(buffer, sizeof(buffer), Arguments::get_dll_dir(),
name)) {
library = os::dll_load(buffer, ebuf, sizeof ebuf);
}
if (library == NULL) { // Try the library path directory.
if (os::dll_build_name(buffer, sizeof(buffer), name)) {
library = os::dll_load(buffer, ebuf, sizeof ebuf);
}
if (library == NULL) {
const char *sub_msg = " on the library path, with error: ";
const char *sub_msg2 = "\nModule java.instrument may be missing from runtime image.";
size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) +
strlen(ebuf) + strlen(sub_msg2) + 1;
char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
if (!agent->is_instrument_lib()) {
jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
} else {
jio_snprintf(buf, len, "%s%s%s%s%s", msg, name, sub_msg, ebuf, sub_msg2);
}
// If we can't find the agent, exit.
vm_exit_during_initialization(buf, NULL);
FREE_C_HEAP_ARRAY(char, buf);
}
}
}
agent->set_os_lib(library);
agent->set_valid();
}
// Find the OnLoad function.
on_load_entry =
CAST_TO_FN_PTR(OnLoadEntry_t, os::find_agent_function(agent,
false,
on_load_symbols,
num_symbol_entries));
return on_load_entry;
}
// Find the JVM_OnLoad entry point
static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
}
// Find the Agent_OnLoad entry point
static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
}
// For backwards compatibility with -Xrun
// Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
// treated like -agentpath:
// Must be called before agent libraries are created
void Threads::convert_vm_init_libraries_to_agents() {
AgentLibrary* agent;
AgentLibrary* next;
for (agent = Arguments::libraries(); agent != NULL; agent = next) {
next = agent->next(); // cache the next agent now as this agent may get moved off this list
OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
// If there is an JVM_OnLoad function it will get called later,
// otherwise see if there is an Agent_OnLoad
if (on_load_entry == NULL) {
on_load_entry = lookup_agent_on_load(agent);
if (on_load_entry != NULL) {
// switch it to the agent list -- so that Agent_OnLoad will be called,
// JVM_OnLoad won't be attempted and Agent_OnUnload will
Arguments::convert_library_to_agent(agent);
} else {
vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
}
}
}
}
// Create agents for -agentlib: -agentpath: and converted -Xrun
// Invokes Agent_OnLoad
// Called very early -- before JavaThreads exist
void Threads::create_vm_init_agents() {
extern struct JavaVM_ main_vm;
AgentLibrary* agent;
JvmtiExport::enter_onload_phase();
for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
// CDS dumping does not support native JVMTI agent.
// CDS dumping supports Java agent if the AllowArchivingWithJavaAgent diagnostic option is specified.
if (Arguments::is_dumping_archive()) {
if(!agent->is_instrument_lib()) {
vm_exit_during_cds_dumping("CDS dumping does not support native JVMTI agent, name", agent->name());
} else if (!AllowArchivingWithJavaAgent) {
vm_exit_during_cds_dumping(
"Must enable AllowArchivingWithJavaAgent in order to run Java agent during CDS dumping");
}
}
OnLoadEntry_t on_load_entry = lookup_agent_on_load(agent);
if (on_load_entry != NULL) {
// Invoke the Agent_OnLoad function
jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
if (err != JNI_OK) {
vm_exit_during_initialization("agent library failed to init", agent->name());
}
} else {
vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
}
}
JvmtiExport::enter_primordial_phase();
}
extern "C" {
typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
}
void Threads::shutdown_vm_agents() {
// Send any Agent_OnUnload notifications
const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
size_t num_symbol_entries = ARRAY_SIZE(on_unload_symbols);
extern struct JavaVM_ main_vm;
for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
// Find the Agent_OnUnload function.
Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
os::find_agent_function(agent,
false,
on_unload_symbols,
num_symbol_entries));
// Invoke the Agent_OnUnload function
if (unload_entry != NULL) {
JavaThread* thread = JavaThread::current();
ThreadToNativeFromVM ttn(thread);
HandleMark hm(thread);
(*unload_entry)(&main_vm);
}
}
}
// Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
// Invokes JVM_OnLoad
void Threads::create_vm_init_libraries() {
extern struct JavaVM_ main_vm;
AgentLibrary* agent;
for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
if (on_load_entry != NULL) {
// Invoke the JVM_OnLoad function
JavaThread* thread = JavaThread::current();
ThreadToNativeFromVM ttn(thread);
HandleMark hm(thread);
jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
if (err != JNI_OK) {
vm_exit_during_initialization("-Xrun library failed to init", agent->name());
}
} else {
vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
}
}
}
// Last thread running calls java.lang.Shutdown.shutdown()
void JavaThread::invoke_shutdown_hooks() {
HandleMark hm(this);
// We could get here with a pending exception, if so clear it now.
if (this->has_pending_exception()) {
this->clear_pending_exception();
}
EXCEPTION_MARK;
Klass* shutdown_klass =
SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
THREAD);
if (shutdown_klass != NULL) {
// SystemDictionary::resolve_or_null will return null if there was
// an exception. If we cannot load the Shutdown class, just don't
// call Shutdown.shutdown() at all. This will mean the shutdown hooks
// won't be run. Note that if a shutdown hook was registered,
// the Shutdown class would have already been loaded
// (Runtime.addShutdownHook will load it).
JavaValue result(T_VOID);
JavaCalls::call_static(&result,
shutdown_klass,
vmSymbols::shutdown_name(),
vmSymbols::void_method_signature(),
THREAD);
}
CLEAR_PENDING_EXCEPTION;
}
// Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
// the program falls off the end of main(). Another VM exit path is through
// vm_exit() when the program calls System.exit() to return a value or when
// there is a serious error in VM. The two shutdown paths are not exactly
// the same, but they share Shutdown.shutdown() at Java level and before_exit()
// and VM_Exit op at VM level.
//
// Shutdown sequence:
// + Shutdown native memory tracking if it is on
// + Wait until we are the last non-daemon thread to execute
// <-- every thing is still working at this moment -->
// + Call java.lang.Shutdown.shutdown(), which will invoke Java level
// shutdown hooks
// + Call before_exit(), prepare for VM exit
// > run VM level shutdown hooks (they are registered through JVM_OnExit(),
// currently the only user of this mechanism is File.deleteOnExit())
// > stop StatSampler, watcher thread,
// post thread end and vm death events to JVMTI,
// stop signal thread
// + Call JavaThread::exit(), it will:
// > release JNI handle blocks, remove stack guard pages
// > remove this thread from Threads list
// <-- no more Java code from this thread after this point -->
// + Stop VM thread, it will bring the remaining VM to a safepoint and stop
// the compiler threads at safepoint
// <-- do not use anything that could get blocked by Safepoint -->
// + Disable tracing at JNI/JVM barriers
// + Set _vm_exited flag for threads that are still running native code
// + Call exit_globals()
// > deletes tty
// > deletes PerfMemory resources
// + Delete this thread
// + Return to caller
bool Threads::destroy_vm() {
JavaThread* thread = JavaThread::current();
#ifdef ASSERT
_vm_complete = false;
#endif
// Wait until we are the last non-daemon thread to execute
{ MonitorLocker nu(Threads_lock);
while (Threads::number_of_non_daemon_threads() > 1)
// This wait should make safepoint checks, wait without a timeout,
// and wait as a suspend-equivalent condition.
nu.wait(0, Mutex::_as_suspend_equivalent_flag);
}
EventShutdown e;
if (e.should_commit()) {
e.set_reason("No remaining non-daemon Java threads");
e.commit();
}
// Hang forever on exit if we are reporting an error.
if (ShowMessageBoxOnError && VMError::is_error_reported()) {
os::infinite_sleep();
}
os::wait_for_keypress_at_exit();
// run Java level shutdown hooks
thread->invoke_shutdown_hooks();
before_exit(thread);
thread->exit(true);
// Stop VM thread.
{
// 4945125 The vm thread comes to a safepoint during exit.
// GC vm_operations can get caught at the safepoint, and the
// heap is unparseable if they are caught. Grab the Heap_lock
// to prevent this. The GC vm_operations will not be able to
// queue until after the vm thread is dead. After this point,
// we'll never emerge out of the safepoint before the VM exits.
MutexLocker ml(Heap_lock, Mutex::_no_safepoint_check_flag);
VMThread::wait_for_vm_thread_exit();
assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
VMThread::destroy();
}
// Now, all Java threads are gone except daemon threads. Daemon threads
// running Java code or in VM are stopped by the Safepoint. However,
// daemon threads executing native code are still running. But they
// will be stopped at native=>Java/VM barriers. Note that we can't
// simply kill or suspend them, as it is inherently deadlock-prone.
VM_Exit::set_vm_exited();
// Clean up ideal graph printers after the VMThread has started
// the final safepoint which will block all the Compiler threads.
// Note that this Thread has already logically exited so the
// clean_up() function's use of a JavaThreadIteratorWithHandle
// would be a problem except set_vm_exited() has remembered the
// shutdown thread which is granted a policy exception.
#if defined(COMPILER2) && !defined(PRODUCT)
IdealGraphPrinter::clean_up();
#endif
notify_vm_shutdown();
// exit_globals() will delete tty
exit_globals();
// We are after VM_Exit::set_vm_exited() so we can't call
// thread->smr_delete() or we will block on the Threads_lock.
// Deleting the shutdown thread here is safe because another
// JavaThread cannot have an active ThreadsListHandle for
// this JavaThread.
delete thread;
#if INCLUDE_JVMCI
if (JVMCICounterSize > 0) {
FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
}
#endif
LogConfiguration::finalize();
return true;
}
jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
if (version == JNI_VERSION_1_1) return JNI_TRUE;
return is_supported_jni_version(version);
}
jboolean Threads::is_supported_jni_version(jint version) {
if (version == JNI_VERSION_1_2) return JNI_TRUE;
if (version == JNI_VERSION_1_4) return JNI_TRUE;
if (version == JNI_VERSION_1_6) return JNI_TRUE;
if (version == JNI_VERSION_1_8) return JNI_TRUE;
if (version == JNI_VERSION_9) return JNI_TRUE;
if (version == JNI_VERSION_10) return JNI_TRUE;
return JNI_FALSE;
}
void Threads::add(JavaThread* p, bool force_daemon) {
// The threads lock must be owned at this point
assert(Threads_lock->owned_by_self(), "must have threads lock");
BarrierSet::barrier_set()->on_thread_attach(p);
// Once a JavaThread is added to the Threads list, smr_delete() has
// to be used to delete it. Otherwise we can just delete it directly.
p->set_on_thread_list();
_number_of_threads++;
oop threadObj = p->threadObj();
bool daemon = true;
// Bootstrapping problem: threadObj can be null for initial
// JavaThread (or for threads attached via JNI)
if ((!force_daemon) && !is_daemon((threadObj))) {
_number_of_non_daemon_threads++;
daemon = false;
}
ThreadService::add_thread(p, daemon);
// Maintain fast thread list
ThreadsSMRSupport::add_thread(p);
// Possible GC point.
Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
}
void Threads::remove(JavaThread* p, bool is_daemon) {
// Reclaim the ObjectMonitors from the om_in_use_list and om_free_list of the moribund thread.
ObjectSynchronizer::om_flush(p);
// Extra scope needed for Thread_lock, so we can check
// that we do not remove thread without safepoint code notice
{ MonitorLocker ml(Threads_lock);
assert(ThreadsSMRSupport::get_java_thread_list()->includes(p), "p must be present");
// Maintain fast thread list
ThreadsSMRSupport::remove_thread(p);
_number_of_threads--;
if (!is_daemon) {
_number_of_non_daemon_threads--;
// Only one thread left, do a notify on the Threads_lock so a thread waiting
// on destroy_vm will wake up.
if (number_of_non_daemon_threads() == 1) {
ml.notify_all();
}
}
ThreadService::remove_thread(p, is_daemon);
// Make sure that safepoint code disregard this thread. This is needed since
// the thread might mess around with locks after this point. This can cause it
// to do callbacks into the safepoint code. However, the safepoint code is not aware
// of this thread since it is removed from the queue.
p->set_terminated_value();
} // unlock Threads_lock
// Since Events::log uses a lock, we grab it outside the Threads_lock
Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
}
// Operations on the Threads list for GC. These are not explicitly locked,
// but the garbage collector must provide a safe context for them to run.
// In particular, these things should never be called when the Threads_lock
// is held by some other thread. (Note: the Safepoint abstraction also
// uses the Threads_lock to guarantee this property. It also makes sure that
// all threads gets blocked when exiting or starting).
void Threads::oops_do(OopClosure* f, CodeBlobClosure* cf) {
ALL_JAVA_THREADS(p) {
p->oops_do(f, cf);
}
VMThread::vm_thread()->oops_do(f, cf);
}
void Threads::change_thread_claim_token() {
if (++_thread_claim_token == 0) {
// On overflow of the token counter, there is a risk of future
// collisions between a new global token value and a stale token
// for a thread, because not all iterations visit all threads.
// (Though it's pretty much a theoretical concern for non-trivial
// token counter sizes.) To deal with the possibility, reset all
// the thread tokens to zero on global token overflow.
struct ResetClaims : public ThreadClosure {
virtual void do_thread(Thread* t) {
t->claim_threads_do(false, 0);
}
} reset_claims;
Threads::threads_do(&reset_claims);
// On overflow, update the global token to non-zero, to
// avoid the special "never claimed" initial thread value.
_thread_claim_token = 1;
}
}
#ifdef ASSERT
void assert_thread_claimed(const char* kind, Thread* t, uintx expected) {
const uintx token = t->threads_do_token();
assert(token == expected,
"%s " PTR_FORMAT " has incorrect value " UINTX_FORMAT " != "
UINTX_FORMAT, kind, p2i(t), token, expected);
}
void Threads::assert_all_threads_claimed() {
ALL_JAVA_THREADS(p) {
assert_thread_claimed("Thread", p, _thread_claim_token);
}
assert_thread_claimed("VMThread", VMThread::vm_thread(), _thread_claim_token);
}
#endif // ASSERT
class ParallelOopsDoThreadClosure : public ThreadClosure {
private:
OopClosure* _f;
CodeBlobClosure* _cf;
public:
ParallelOopsDoThreadClosure(OopClosure* f, CodeBlobClosure* cf) : _f(f), _cf(cf) {}
void do_thread(Thread* t) {
t->oops_do(_f, _cf);
}
};
void Threads::possibly_parallel_oops_do(bool is_par, OopClosure* f, CodeBlobClosure* cf) {
ParallelOopsDoThreadClosure tc(f, cf);
possibly_parallel_threads_do(is_par, &tc);
}
void Threads::nmethods_do(CodeBlobClosure* cf) {
ALL_JAVA_THREADS(p) {
// This is used by the code cache sweeper to mark nmethods that are active
// on the stack of a Java thread. Ignore the sweeper thread itself to avoid
// marking CodeCacheSweeperThread::_scanned_compiled_method as active.
if(!p->is_Code_cache_sweeper_thread()) {
p->nmethods_do(cf);
}
}
}
void Threads::metadata_do(MetadataClosure* f) {
ALL_JAVA_THREADS(p) {
p->metadata_do(f);
}
}
class ThreadHandlesClosure : public ThreadClosure {
void (*_f)(Metadata*);
public:
ThreadHandlesClosure(void f(Metadata*)) : _f(f) {}
virtual void do_thread(Thread* thread) {
thread->metadata_handles_do(_f);
}
};
void Threads::metadata_handles_do(void f(Metadata*)) {
// Only walk the Handles in Thread.
ThreadHandlesClosure handles_closure(f);
threads_do(&handles_closure);
}
// Get count Java threads that are waiting to enter the specified monitor.
GrowableArray<JavaThread*>* Threads::get_pending_threads(ThreadsList * t_list,
int count,
address monitor) {
GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
int i = 0;
DO_JAVA_THREADS(t_list, p) {
if (!p->can_call_java()) continue;
address pending = (address)p->current_pending_monitor();
if (pending == monitor) { // found a match
if (i < count) result->append(p); // save the first count matches
i++;
}
}
return result;
}
JavaThread *Threads::owning_thread_from_monitor_owner(ThreadsList * t_list,
address owner) {
// NULL owner means not locked so we can skip the search
if (owner == NULL) return NULL;
DO_JAVA_THREADS(t_list, p) {
// first, see if owner is the address of a Java thread
if (owner == (address)p) return p;
}
// Cannot assert on lack of success here since this function may be
// used by code that is trying to report useful problem information
// like deadlock detection.
if (UseHeavyMonitors) return NULL;
// If we didn't find a matching Java thread and we didn't force use of
// heavyweight monitors, then the owner is the stack address of the
// Lock Word in the owning Java thread's stack.
//
JavaThread* the_owner = NULL;
DO_JAVA_THREADS(t_list, q) {
if (q->is_lock_owned(owner)) {
the_owner = q;
break;
}
}
// cannot assert on lack of success here; see above comment
return the_owner;
}
// Threads::print_on() is called at safepoint by VM_PrintThreads operation.
void Threads::print_on(outputStream* st, bool print_stacks,
bool internal_format, bool print_concurrent_locks,
bool print_extended_info) {
char buf[32];
st->print_raw_cr(os::local_time_string(buf, sizeof(buf)));
st->print_cr("Full thread dump %s (%s %s):",
VM_Version::vm_name(),
VM_Version::vm_release(),
VM_Version::vm_info_string());
st->cr();
#if INCLUDE_SERVICES
// Dump concurrent locks
ConcurrentLocksDump concurrent_locks;
if (print_concurrent_locks) {
concurrent_locks.dump_at_safepoint();
}
#endif // INCLUDE_SERVICES
ThreadsSMRSupport::print_info_on(st);
st->cr();
ALL_JAVA_THREADS(p) {
ResourceMark rm;
p->print_on(st, print_extended_info);
if (print_stacks) {
if (internal_format) {
p->trace_stack();
} else {
p->print_stack_on(st);
}
}
st->cr();
#if INCLUDE_SERVICES
if (print_concurrent_locks) {
concurrent_locks.print_locks_on(p, st);
}
#endif // INCLUDE_SERVICES
}
VMThread::vm_thread()->print_on(st);
st->cr();
Universe::heap()->print_gc_threads_on(st);
WatcherThread* wt = WatcherThread::watcher_thread();
if (wt != NULL) {
wt->print_on(st);
st->cr();
}
st->flush();
}
void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
int buflen, bool* found_current) {
if (this_thread != NULL) {
bool is_current = (current == this_thread);
*found_current = *found_current || is_current;
st->print("%s", is_current ? "=>" : " ");
st->print(PTR_FORMAT, p2i(this_thread));
st->print(" ");
this_thread->print_on_error(st, buf, buflen);
st->cr();
}
}
class PrintOnErrorClosure : public ThreadClosure {
outputStream* _st;
Thread* _current;
char* _buf;
int _buflen;
bool* _found_current;
public:
PrintOnErrorClosure(outputStream* st, Thread* current, char* buf,
int buflen, bool* found_current) :
_st(st), _current(current), _buf(buf), _buflen(buflen), _found_current(found_current) {}
virtual void do_thread(Thread* thread) {
Threads::print_on_error(thread, _st, _current, _buf, _buflen, _found_current);
}
};
// Threads::print_on_error() is called by fatal error handler. It's possible
// that VM is not at safepoint and/or current thread is inside signal handler.
// Don't print stack trace, as the stack may not be walkable. Don't allocate
// memory (even in resource area), it might deadlock the error handler.
void Threads::print_on_error(outputStream* st, Thread* current, char* buf,
int buflen) {
ThreadsSMRSupport::print_info_on(st);
st->cr();
bool found_current = false;
st->print_cr("Java Threads: ( => current thread )");
ALL_JAVA_THREADS(thread) {
print_on_error(thread, st, current, buf, buflen, &found_current);
}
st->cr();
st->print_cr("Other Threads:");
print_on_error(VMThread::vm_thread(), st, current, buf, buflen, &found_current);
print_on_error(WatcherThread::watcher_thread(), st, current, buf, buflen, &found_current);
PrintOnErrorClosure print_closure(st, current, buf, buflen, &found_current);
Universe::heap()->gc_threads_do(&print_closure);
if (!found_current) {
st->cr();
st->print("=>" PTR_FORMAT " (exited) ", p2i(current));
current->print_on_error(st, buf, buflen);
st->cr();
}
st->cr();
st->print_cr("Threads with active compile tasks:");
print_threads_compiling(st, buf, buflen);
}
void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen, bool short_form) {
ALL_JAVA_THREADS(thread) {
if (thread->is_Compiler_thread()) {
CompilerThread* ct = (CompilerThread*) thread;
// Keep task in local variable for NULL check.
// ct->_task might be set to NULL by concurring compiler thread
// because it completed the compilation. The task is never freed,
// though, just returned to a free list.
CompileTask* task = ct->task();
if (task != NULL) {
thread->print_name_on_error(st, buf, buflen);
st->print(" ");
task->print(st, NULL, short_form, true);
}
}
}
}
// Internal SpinLock and Mutex
// Based on ParkEvent
// Ad-hoc mutual exclusion primitives: SpinLock and Mux
//
// We employ SpinLocks _only for low-contention, fixed-length
// short-duration critical sections where we're concerned
// about native mutex_t or HotSpot Mutex:: latency.
// The mux construct provides a spin-then-block mutual exclusion
// mechanism.
//
// Testing has shown that contention on the ListLock guarding gFreeList
// is common. If we implement ListLock as a simple SpinLock it's common
// for the JVM to devolve to yielding with little progress. This is true
// despite the fact that the critical sections protected by ListLock are
// extremely short.
//
// TODO-FIXME: ListLock should be of type SpinLock.
// We should make this a 1st-class type, integrated into the lock
// hierarchy as leaf-locks. Critically, the SpinLock structure
// should have sufficient padding to avoid false-sharing and excessive
// cache-coherency traffic.
typedef volatile int SpinLockT;
void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
if (Atomic::cmpxchg(adr, 0, 1) == 0) {
return; // normal fast-path return
}
// Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
int ctr = 0;
int Yields = 0;
for (;;) {
while (*adr != 0) {
++ctr;
if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
if (Yields > 5) {
os::naked_short_sleep(1);
} else {
os::naked_yield();
++Yields;
}
} else {
SpinPause();
}
}
if (Atomic::cmpxchg(adr, 0, 1) == 0) return;
}
}
void Thread::SpinRelease(volatile int * adr) {
assert(*adr != 0, "invariant");
OrderAccess::fence(); // guarantee at least release consistency.
// Roach-motel semantics.
// It's safe if subsequent LDs and STs float "up" into the critical section,
// but prior LDs and STs within the critical section can't be allowed
// to reorder or float past the ST that releases the lock.
// Loads and stores in the critical section - which appear in program
// order before the store that releases the lock - must also appear
// before the store that releases the lock in memory visibility order.
// Conceptually we need a #loadstore|#storestore "release" MEMBAR before
// the ST of 0 into the lock-word which releases the lock, so fence
// more than covers this on all platforms.
*adr = 0;
}
// muxAcquire and muxRelease:
//
// * muxAcquire and muxRelease support a single-word lock-word construct.
// The LSB of the word is set IFF the lock is held.
// The remainder of the word points to the head of a singly-linked list
// of threads blocked on the lock.
//
// * The current implementation of muxAcquire-muxRelease uses its own
// dedicated Thread._MuxEvent instance. If we're interested in
// minimizing the peak number of extant ParkEvent instances then
// we could eliminate _MuxEvent and "borrow" _ParkEvent as long
// as certain invariants were satisfied. Specifically, care would need
// to be taken with regards to consuming unpark() "permits".
// A safe rule of thumb is that a thread would never call muxAcquire()
// if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
// park(). Otherwise the _ParkEvent park() operation in muxAcquire() could
// consume an unpark() permit intended for monitorenter, for instance.
// One way around this would be to widen the restricted-range semaphore
// implemented in park(). Another alternative would be to provide
// multiple instances of the PlatformEvent() for each thread. One
// instance would be dedicated to muxAcquire-muxRelease, for instance.
//
// * Usage:
// -- Only as leaf locks
// -- for short-term locking only as muxAcquire does not perform
// thread state transitions.
//
// Alternatives:
// * We could implement muxAcquire and muxRelease with MCS or CLH locks
// but with parking or spin-then-park instead of pure spinning.
// * Use Taura-Oyama-Yonenzawa locks.
// * It's possible to construct a 1-0 lock if we encode the lockword as
// (List,LockByte). Acquire will CAS the full lockword while Release
// will STB 0 into the LockByte. The 1-0 scheme admits stranding, so
// acquiring threads use timers (ParkTimed) to detect and recover from
// the stranding window. Thread/Node structures must be aligned on 256-byte
// boundaries by using placement-new.
// * Augment MCS with advisory back-link fields maintained with CAS().
// Pictorially: LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
// The validity of the backlinks must be ratified before we trust the value.
// If the backlinks are invalid the exiting thread must back-track through the
// the forward links, which are always trustworthy.
// * Add a successor indication. The LockWord is currently encoded as
// (List, LOCKBIT:1). We could also add a SUCCBIT or an explicit _succ variable
// to provide the usual futile-wakeup optimization.
// See RTStt for details.
//
const intptr_t LOCKBIT = 1;
void Thread::muxAcquire(volatile intptr_t * Lock, const char * LockName) {
intptr_t w = Atomic::cmpxchg(Lock, (intptr_t)0, LOCKBIT);
if (w == 0) return;
if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(Lock, w, w|LOCKBIT) == w) {
return;
}
ParkEvent * const Self = Thread::current()->_MuxEvent;
assert((intptr_t(Self) & LOCKBIT) == 0, "invariant");
for (;;) {
int its = (os::is_MP() ? 100 : 0) + 1;
// Optional spin phase: spin-then-park strategy
while (--its >= 0) {
w = *Lock;
if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(Lock, w, w|LOCKBIT) == w) {
return;
}
}
Self->reset();
Self->OnList = intptr_t(Lock);
// The following fence() isn't _strictly necessary as the subsequent
// CAS() both serializes execution and ratifies the fetched *Lock value.
OrderAccess::fence();
for (;;) {
w = *Lock;
if ((w & LOCKBIT) == 0) {
if (Atomic::cmpxchg(Lock, w, w|LOCKBIT) == w) {
Self->OnList = 0; // hygiene - allows stronger asserts
return;
}
continue; // Interference -- *Lock changed -- Just retry
}
assert(w & LOCKBIT, "invariant");
Self->ListNext = (ParkEvent *) (w & ~LOCKBIT);
if (Atomic::cmpxchg(Lock, w, intptr_t(Self)|LOCKBIT) == w) break;
}
while (Self->OnList != 0) {
Self->park();
}
}
}
// Release() must extract a successor from the list and then wake that thread.
// It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
// similar to that used by ParkEvent::Allocate() and ::Release(). DMR-based
// Release() would :
// (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
// (B) Extract a successor from the private list "in-hand"
// (C) attempt to CAS() the residual back into *Lock over null.
// If there were any newly arrived threads and the CAS() would fail.
// In that case Release() would detach the RATs, re-merge the list in-hand
// with the RATs and repeat as needed. Alternately, Release() might
// detach and extract a successor, but then pass the residual list to the wakee.
// The wakee would be responsible for reattaching and remerging before it
// competed for the lock.
//
// Both "pop" and DMR are immune from ABA corruption -- there can be
// multiple concurrent pushers, but only one popper or detacher.
// This implementation pops from the head of the list. This is unfair,
// but tends to provide excellent throughput as hot threads remain hot.
// (We wake recently run threads first).
//
// All paths through muxRelease() will execute a CAS.
// Release consistency -- We depend on the CAS in muxRelease() to provide full
// bidirectional fence/MEMBAR semantics, ensuring that all prior memory operations
// executed within the critical section are complete and globally visible before the
// store (CAS) to the lock-word that releases the lock becomes globally visible.
void Thread::muxRelease(volatile intptr_t * Lock) {
for (;;) {
const intptr_t w = Atomic::cmpxchg(Lock, LOCKBIT, (intptr_t)0);
assert(w & LOCKBIT, "invariant");
if (w == LOCKBIT) return;
ParkEvent * const List = (ParkEvent *) (w & ~LOCKBIT);
assert(List != NULL, "invariant");
assert(List->OnList == intptr_t(Lock), "invariant");
ParkEvent * const nxt = List->ListNext;
guarantee((intptr_t(nxt) & LOCKBIT) == 0, "invariant");
// The following CAS() releases the lock and pops the head element.
// The CAS() also ratifies the previously fetched lock-word value.
if (Atomic::cmpxchg(Lock, w, intptr_t(nxt)) != w) {
continue;
}
List->OnList = 0;
OrderAccess::fence();
List->unpark();
return;
}
}
void Threads::verify() {
ALL_JAVA_THREADS(p) {
p->verify();
}
VMThread* thread = VMThread::vm_thread();
if (thread != NULL) thread->verify();
}