author | kvn |
Thu, 20 Feb 2014 12:20:56 -0800 | |
changeset 22881 | b16d7faa638d |
parent 22796 | bb0ea482a99e |
parent 22876 | 57aa8995d43b |
child 24424 | 2658d7834c6e |
permissions | -rw-r--r-- |
1 | 1 |
/* |
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* Copyright (c) 1998, 2014, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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* |
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*/ |
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||
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#include "precompiled.hpp" |
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#include "classfile/vmSymbols.hpp" |
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#include "memory/resourceArea.hpp" |
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#include "oops/markOop.hpp" |
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#include "oops/oop.inline.hpp" |
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#include "runtime/biasedLocking.hpp" |
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#include "runtime/handles.inline.hpp" |
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#include "runtime/interfaceSupport.hpp" |
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#include "runtime/mutexLocker.hpp" |
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#include "runtime/objectMonitor.hpp" |
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#include "runtime/objectMonitor.inline.hpp" |
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#include "runtime/osThread.hpp" |
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#include "runtime/stubRoutines.hpp" |
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#include "runtime/synchronizer.hpp" |
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#include "runtime/thread.inline.hpp" |
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#include "utilities/dtrace.hpp" |
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#include "utilities/events.hpp" |
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#include "utilities/preserveException.hpp" |
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#ifdef TARGET_OS_FAMILY_linux |
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# include "os_linux.inline.hpp" |
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#endif |
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#ifdef TARGET_OS_FAMILY_solaris |
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# include "os_solaris.inline.hpp" |
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#endif |
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#ifdef TARGET_OS_FAMILY_windows |
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# include "os_windows.inline.hpp" |
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#endif |
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#ifdef TARGET_OS_FAMILY_bsd |
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# include "os_bsd.inline.hpp" |
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#endif |
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#if defined(__GNUC__) && !defined(PPC64) |
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// Need to inhibit inlining for older versions of GCC to avoid build-time failures |
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#define ATTR __attribute__((noinline)) |
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#else |
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#define ATTR |
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#endif |
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// The "core" versions of monitor enter and exit reside in this file. |
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// The interpreter and compilers contain specialized transliterated |
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// variants of the enter-exit fast-path operations. See i486.ad fast_lock(), |
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// for instance. If you make changes here, make sure to modify the |
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// interpreter, and both C1 and C2 fast-path inline locking code emission. |
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// |
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// |
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// ----------------------------------------------------------------------------- |
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#ifdef DTRACE_ENABLED |
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// Only bother with this argument setup if dtrace is available |
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// TODO-FIXME: probes should not fire when caller is _blocked. assert() accordingly. |
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#define DTRACE_MONITOR_PROBE_COMMON(obj, thread) \ |
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char* bytes = NULL; \ |
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int len = 0; \ |
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jlong jtid = SharedRuntime::get_java_tid(thread); \ |
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Symbol* klassname = ((oop)(obj))->klass()->name(); \ |
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if (klassname != NULL) { \ |
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bytes = (char*)klassname->bytes(); \ |
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len = klassname->utf8_length(); \ |
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} |
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#define DTRACE_MONITOR_WAIT_PROBE(monitor, obj, thread, millis) \ |
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{ \ |
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if (DTraceMonitorProbes) { \ |
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DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ |
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HOTSPOT_MONITOR_WAIT(jtid, \ |
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(uintptr_t)(monitor), bytes, len, (millis)); \ |
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} \ |
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} |
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#define HOTSPOT_MONITOR_PROBE_waited HOTSPOT_MONITOR_WAITED |
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#define DTRACE_MONITOR_PROBE(probe, monitor, obj, thread) \ |
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{ \ |
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if (DTraceMonitorProbes) { \ |
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DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ |
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HOTSPOT_MONITOR_PROBE_##probe(jtid, /* probe = waited */ \ |
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(uintptr_t)(monitor), bytes, len); \ |
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} \ |
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} |
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#else // ndef DTRACE_ENABLED |
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#define DTRACE_MONITOR_WAIT_PROBE(obj, thread, millis, mon) {;} |
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#define DTRACE_MONITOR_PROBE(probe, obj, thread, mon) {;} |
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#endif // ndef DTRACE_ENABLED |
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// This exists only as a workaround of dtrace bug 6254741 |
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int dtrace_waited_probe(ObjectMonitor* monitor, Handle obj, Thread* thr) { |
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DTRACE_MONITOR_PROBE(waited, monitor, obj(), thr); |
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return 0; |
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} |
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#define NINFLATIONLOCKS 256 |
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static volatile intptr_t InflationLocks [NINFLATIONLOCKS] ; |
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ObjectMonitor * ObjectSynchronizer::gBlockList = NULL ; |
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ObjectMonitor * volatile ObjectSynchronizer::gFreeList = NULL ; |
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ObjectMonitor * volatile ObjectSynchronizer::gOmInUseList = NULL ; |
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int ObjectSynchronizer::gOmInUseCount = 0; |
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static volatile intptr_t ListLock = 0 ; // protects global monitor free-list cache |
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static volatile int MonitorFreeCount = 0 ; // # on gFreeList |
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static volatile int MonitorPopulation = 0 ; // # Extant -- in circulation |
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#define CHAINMARKER (cast_to_oop<intptr_t>(-1)) |
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// ----------------------------------------------------------------------------- |
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// Fast Monitor Enter/Exit |
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// This the fast monitor enter. The interpreter and compiler use |
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// some assembly copies of this code. Make sure update those code |
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// if the following function is changed. The implementation is |
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// extremely sensitive to race condition. Be careful. |
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void ObjectSynchronizer::fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias, TRAPS) { |
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if (UseBiasedLocking) { |
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if (!SafepointSynchronize::is_at_safepoint()) { |
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BiasedLocking::Condition cond = BiasedLocking::revoke_and_rebias(obj, attempt_rebias, THREAD); |
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if (cond == BiasedLocking::BIAS_REVOKED_AND_REBIASED) { |
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return; |
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} |
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} else { |
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assert(!attempt_rebias, "can not rebias toward VM thread"); |
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BiasedLocking::revoke_at_safepoint(obj); |
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} |
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assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
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} |
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slow_enter (obj, lock, THREAD) ; |
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} |
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void ObjectSynchronizer::fast_exit(oop object, BasicLock* lock, TRAPS) { |
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assert(!object->mark()->has_bias_pattern(), "should not see bias pattern here"); |
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// if displaced header is null, the previous enter is recursive enter, no-op |
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markOop dhw = lock->displaced_header(); |
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markOop mark ; |
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if (dhw == NULL) { |
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// Recursive stack-lock. |
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// Diagnostics -- Could be: stack-locked, inflating, inflated. |
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mark = object->mark() ; |
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assert (!mark->is_neutral(), "invariant") ; |
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if (mark->has_locker() && mark != markOopDesc::INFLATING()) { |
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assert(THREAD->is_lock_owned((address)mark->locker()), "invariant") ; |
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} |
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if (mark->has_monitor()) { |
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ObjectMonitor * m = mark->monitor() ; |
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assert(((oop)(m->object()))->mark() == mark, "invariant") ; |
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assert(m->is_entered(THREAD), "invariant") ; |
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} |
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return ; |
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} |
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mark = object->mark() ; |
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// If the object is stack-locked by the current thread, try to |
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// swing the displaced header from the box back to the mark. |
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if (mark == (markOop) lock) { |
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assert (dhw->is_neutral(), "invariant") ; |
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if ((markOop) Atomic::cmpxchg_ptr (dhw, object->mark_addr(), mark) == mark) { |
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TEVENT (fast_exit: release stacklock) ; |
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return; |
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} |
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} |
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ObjectSynchronizer::inflate(THREAD, object)->exit (true, THREAD) ; |
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} |
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// ----------------------------------------------------------------------------- |
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// Interpreter/Compiler Slow Case |
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// This routine is used to handle interpreter/compiler slow case |
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// We don't need to use fast path here, because it must have been |
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// failed in the interpreter/compiler code. |
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void ObjectSynchronizer::slow_enter(Handle obj, BasicLock* lock, TRAPS) { |
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markOop mark = obj->mark(); |
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assert(!mark->has_bias_pattern(), "should not see bias pattern here"); |
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if (mark->is_neutral()) { |
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// Anticipate successful CAS -- the ST of the displaced mark must |
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// be visible <= the ST performed by the CAS. |
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lock->set_displaced_header(mark); |
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if (mark == (markOop) Atomic::cmpxchg_ptr(lock, obj()->mark_addr(), mark)) { |
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TEVENT (slow_enter: release stacklock) ; |
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return ; |
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} |
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// Fall through to inflate() ... |
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} else |
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if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { |
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assert(lock != mark->locker(), "must not re-lock the same lock"); |
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assert(lock != (BasicLock*)obj->mark(), "don't relock with same BasicLock"); |
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lock->set_displaced_header(NULL); |
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return; |
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} |
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#if 0 |
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// The following optimization isn't particularly useful. |
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if (mark->has_monitor() && mark->monitor()->is_entered(THREAD)) { |
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lock->set_displaced_header (NULL) ; |
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return ; |
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} |
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#endif |
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// The object header will never be displaced to this lock, |
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// so it does not matter what the value is, except that it |
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// must be non-zero to avoid looking like a re-entrant lock, |
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// and must not look locked either. |
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lock->set_displaced_header(markOopDesc::unused_mark()); |
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ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD); |
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} |
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||
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// This routine is used to handle interpreter/compiler slow case |
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// We don't need to use fast path here, because it must have |
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// failed in the interpreter/compiler code. Simply use the heavy |
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// weight monitor should be ok, unless someone find otherwise. |
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void ObjectSynchronizer::slow_exit(oop object, BasicLock* lock, TRAPS) { |
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fast_exit (object, lock, THREAD) ; |
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} |
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// ----------------------------------------------------------------------------- |
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// Class Loader support to workaround deadlocks on the class loader lock objects |
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// Also used by GC |
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// complete_exit()/reenter() are used to wait on a nested lock |
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// i.e. to give up an outer lock completely and then re-enter |
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// Used when holding nested locks - lock acquisition order: lock1 then lock2 |
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// 1) complete_exit lock1 - saving recursion count |
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// 2) wait on lock2 |
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// 3) when notified on lock2, unlock lock2 |
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// 4) reenter lock1 with original recursion count |
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// 5) lock lock2 |
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// NOTE: must use heavy weight monitor to handle complete_exit/reenter() |
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intptr_t ObjectSynchronizer::complete_exit(Handle obj, TRAPS) { |
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TEVENT (complete_exit) ; |
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if (UseBiasedLocking) { |
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BiasedLocking::revoke_and_rebias(obj, false, THREAD); |
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assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
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} |
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ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); |
262 |
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return monitor->complete_exit(THREAD); |
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} |
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265 |
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// NOTE: must use heavy weight monitor to handle complete_exit/reenter() |
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void ObjectSynchronizer::reenter(Handle obj, intptr_t recursion, TRAPS) { |
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TEVENT (reenter) ; |
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if (UseBiasedLocking) { |
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BiasedLocking::revoke_and_rebias(obj, false, THREAD); |
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271 |
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
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} |
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273 |
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274 |
ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); |
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275 |
||
276 |
monitor->reenter(recursion, THREAD); |
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} |
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278 |
// ----------------------------------------------------------------------------- |
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279 |
// JNI locks on java objects |
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280 |
// NOTE: must use heavy weight monitor to handle jni monitor enter |
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281 |
void ObjectSynchronizer::jni_enter(Handle obj, TRAPS) { // possible entry from jni enter |
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282 |
// the current locking is from JNI instead of Java code |
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283 |
TEVENT (jni_enter) ; |
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284 |
if (UseBiasedLocking) { |
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285 |
BiasedLocking::revoke_and_rebias(obj, false, THREAD); |
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286 |
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
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287 |
} |
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288 |
THREAD->set_current_pending_monitor_is_from_java(false); |
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289 |
ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD); |
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290 |
THREAD->set_current_pending_monitor_is_from_java(true); |
|
291 |
} |
|
292 |
||
293 |
// NOTE: must use heavy weight monitor to handle jni monitor enter |
|
294 |
bool ObjectSynchronizer::jni_try_enter(Handle obj, Thread* THREAD) { |
|
295 |
if (UseBiasedLocking) { |
|
296 |
BiasedLocking::revoke_and_rebias(obj, false, THREAD); |
|
297 |
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
|
1 | 298 |
} |
299 |
||
6975 | 300 |
ObjectMonitor* monitor = ObjectSynchronizer::inflate_helper(obj()); |
301 |
return monitor->try_enter(THREAD); |
|
302 |
} |
|
303 |
||
304 |
||
305 |
// NOTE: must use heavy weight monitor to handle jni monitor exit |
|
306 |
void ObjectSynchronizer::jni_exit(oop obj, Thread* THREAD) { |
|
307 |
TEVENT (jni_exit) ; |
|
308 |
if (UseBiasedLocking) { |
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Handle h_obj(THREAD, obj); |
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BiasedLocking::revoke_and_rebias(h_obj, false, THREAD); |
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311 |
obj = h_obj(); |
6975 | 312 |
} |
313 |
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
|
314 |
||
315 |
ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj); |
|
316 |
// If this thread has locked the object, exit the monitor. Note: can't use |
|
317 |
// monitor->check(CHECK); must exit even if an exception is pending. |
|
318 |
if (monitor->check(THREAD)) { |
|
18025 | 319 |
monitor->exit(true, THREAD); |
1 | 320 |
} |
6975 | 321 |
} |
322 |
||
323 |
// ----------------------------------------------------------------------------- |
|
324 |
// Internal VM locks on java objects |
|
325 |
// standard constructor, allows locking failures |
|
326 |
ObjectLocker::ObjectLocker(Handle obj, Thread* thread, bool doLock) { |
|
327 |
_dolock = doLock; |
|
328 |
_thread = thread; |
|
329 |
debug_only(if (StrictSafepointChecks) _thread->check_for_valid_safepoint_state(false);) |
|
330 |
_obj = obj; |
|
1 | 331 |
|
6975 | 332 |
if (_dolock) { |
333 |
TEVENT (ObjectLocker) ; |
|
334 |
||
335 |
ObjectSynchronizer::fast_enter(_obj, &_lock, false, _thread); |
|
336 |
} |
|
337 |
} |
|
338 |
||
339 |
ObjectLocker::~ObjectLocker() { |
|
340 |
if (_dolock) { |
|
341 |
ObjectSynchronizer::fast_exit(_obj(), &_lock, _thread); |
|
342 |
} |
|
343 |
} |
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1 | 344 |
|
345 |
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6975 | 346 |
// ----------------------------------------------------------------------------- |
347 |
// Wait/Notify/NotifyAll |
|
348 |
// NOTE: must use heavy weight monitor to handle wait() |
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int ObjectSynchronizer::wait(Handle obj, jlong millis, TRAPS) { |
6975 | 350 |
if (UseBiasedLocking) { |
351 |
BiasedLocking::revoke_and_rebias(obj, false, THREAD); |
|
352 |
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
|
353 |
} |
|
354 |
if (millis < 0) { |
|
355 |
TEVENT (wait - throw IAX) ; |
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THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); |
6975 | 357 |
} |
358 |
ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); |
|
359 |
DTRACE_MONITOR_WAIT_PROBE(monitor, obj(), THREAD, millis); |
|
360 |
monitor->wait(millis, true, THREAD); |
|
361 |
||
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22551
diff
changeset
|
362 |
// This dummy call is in place to get around dtrace bug 6254741. Once |
e043208c9d93
8030808: dtrace/hotspot/Monitors/Monitors001 fails in product builds on solaris-sparc
fparain
parents:
22551
diff
changeset
|
363 |
// that's fixed we can uncomment the following line, remove the call |
e043208c9d93
8030808: dtrace/hotspot/Monitors/Monitors001 fails in product builds on solaris-sparc
fparain
parents:
22551
diff
changeset
|
364 |
// and change this function back into a "void" func. |
6975 | 365 |
// DTRACE_MONITOR_PROBE(waited, monitor, obj(), THREAD); |
22743
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22551
diff
changeset
|
366 |
return dtrace_waited_probe(monitor, obj, THREAD); |
6975 | 367 |
} |
1 | 368 |
|
6975 | 369 |
void ObjectSynchronizer::waitUninterruptibly (Handle obj, jlong millis, TRAPS) { |
370 |
if (UseBiasedLocking) { |
|
371 |
BiasedLocking::revoke_and_rebias(obj, false, THREAD); |
|
372 |
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
|
373 |
} |
|
374 |
if (millis < 0) { |
|
375 |
TEVENT (wait - throw IAX) ; |
|
376 |
THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); |
|
377 |
} |
|
378 |
ObjectSynchronizer::inflate(THREAD, obj()) -> wait(millis, false, THREAD) ; |
|
379 |
} |
|
380 |
||
381 |
void ObjectSynchronizer::notify(Handle obj, TRAPS) { |
|
382 |
if (UseBiasedLocking) { |
|
383 |
BiasedLocking::revoke_and_rebias(obj, false, THREAD); |
|
384 |
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
|
385 |
} |
|
1 | 386 |
|
6975 | 387 |
markOop mark = obj->mark(); |
388 |
if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { |
|
389 |
return; |
|
390 |
} |
|
391 |
ObjectSynchronizer::inflate(THREAD, obj())->notify(THREAD); |
|
392 |
} |
|
1 | 393 |
|
6975 | 394 |
// NOTE: see comment of notify() |
395 |
void ObjectSynchronizer::notifyall(Handle obj, TRAPS) { |
|
396 |
if (UseBiasedLocking) { |
|
397 |
BiasedLocking::revoke_and_rebias(obj, false, THREAD); |
|
398 |
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
|
399 |
} |
|
400 |
||
401 |
markOop mark = obj->mark(); |
|
402 |
if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { |
|
403 |
return; |
|
404 |
} |
|
405 |
ObjectSynchronizer::inflate(THREAD, obj())->notifyAll(THREAD); |
|
406 |
} |
|
407 |
||
408 |
// ----------------------------------------------------------------------------- |
|
409 |
// Hash Code handling |
|
410 |
// |
|
1 | 411 |
// Performance concern: |
412 |
// OrderAccess::storestore() calls release() which STs 0 into the global volatile |
|
413 |
// OrderAccess::Dummy variable. This store is unnecessary for correctness. |
|
414 |
// Many threads STing into a common location causes considerable cache migration |
|
415 |
// or "sloshing" on large SMP system. As such, I avoid using OrderAccess::storestore() |
|
416 |
// until it's repaired. In some cases OrderAccess::fence() -- which incurs local |
|
417 |
// latency on the executing processor -- is a better choice as it scales on SMP |
|
418 |
// systems. See http://blogs.sun.com/dave/entry/biased_locking_in_hotspot for a |
|
419 |
// discussion of coherency costs. Note that all our current reference platforms |
|
420 |
// provide strong ST-ST order, so the issue is moot on IA32, x64, and SPARC. |
|
421 |
// |
|
422 |
// As a general policy we use "volatile" to control compiler-based reordering |
|
423 |
// and explicit fences (barriers) to control for architectural reordering performed |
|
424 |
// by the CPU(s) or platform. |
|
425 |
||
426 |
struct SharedGlobals { |
|
427 |
// These are highly shared mostly-read variables. |
|
428 |
// To avoid false-sharing they need to be the sole occupants of a $ line. |
|
429 |
double padPrefix [8]; |
|
430 |
volatile int stwRandom ; |
|
431 |
volatile int stwCycle ; |
|
432 |
||
433 |
// Hot RW variables -- Sequester to avoid false-sharing |
|
434 |
double padSuffix [16]; |
|
435 |
volatile int hcSequence ; |
|
436 |
double padFinal [8] ; |
|
437 |
} ; |
|
438 |
||
439 |
static SharedGlobals GVars ; |
|
5710 | 440 |
static int MonitorScavengeThreshold = 1000000 ; |
441 |
static volatile int ForceMonitorScavenge = 0 ; // Scavenge required and pending |
|
1 | 442 |
|
6975 | 443 |
static markOop ReadStableMark (oop obj) { |
444 |
markOop mark = obj->mark() ; |
|
445 |
if (!mark->is_being_inflated()) { |
|
446 |
return mark ; // normal fast-path return |
|
447 |
} |
|
1 | 448 |
|
6975 | 449 |
int its = 0 ; |
450 |
for (;;) { |
|
451 |
markOop mark = obj->mark() ; |
|
452 |
if (!mark->is_being_inflated()) { |
|
453 |
return mark ; // normal fast-path return |
|
454 |
} |
|
455 |
||
456 |
// The object is being inflated by some other thread. |
|
457 |
// The caller of ReadStableMark() must wait for inflation to complete. |
|
458 |
// Avoid live-lock |
|
459 |
// TODO: consider calling SafepointSynchronize::do_call_back() while |
|
460 |
// spinning to see if there's a safepoint pending. If so, immediately |
|
461 |
// yielding or blocking would be appropriate. Avoid spinning while |
|
462 |
// there is a safepoint pending. |
|
463 |
// TODO: add inflation contention performance counters. |
|
464 |
// TODO: restrict the aggregate number of spinners. |
|
1 | 465 |
|
6975 | 466 |
++its ; |
467 |
if (its > 10000 || !os::is_MP()) { |
|
468 |
if (its & 1) { |
|
469 |
os::NakedYield() ; |
|
470 |
TEVENT (Inflate: INFLATING - yield) ; |
|
471 |
} else { |
|
472 |
// Note that the following code attenuates the livelock problem but is not |
|
473 |
// a complete remedy. A more complete solution would require that the inflating |
|
474 |
// thread hold the associated inflation lock. The following code simply restricts |
|
475 |
// the number of spinners to at most one. We'll have N-2 threads blocked |
|
476 |
// on the inflationlock, 1 thread holding the inflation lock and using |
|
477 |
// a yield/park strategy, and 1 thread in the midst of inflation. |
|
478 |
// A more refined approach would be to change the encoding of INFLATING |
|
479 |
// to allow encapsulation of a native thread pointer. Threads waiting for |
|
480 |
// inflation to complete would use CAS to push themselves onto a singly linked |
|
481 |
// list rooted at the markword. Once enqueued, they'd loop, checking a per-thread flag |
|
482 |
// and calling park(). When inflation was complete the thread that accomplished inflation |
|
483 |
// would detach the list and set the markword to inflated with a single CAS and |
|
484 |
// then for each thread on the list, set the flag and unpark() the thread. |
|
485 |
// This is conceptually similar to muxAcquire-muxRelease, except that muxRelease |
|
486 |
// wakes at most one thread whereas we need to wake the entire list. |
|
20282
7f9cbdf89af2
7195622: CheckUnhandledOops has limited usefulness now
hseigel
parents:
18025
diff
changeset
|
487 |
int ix = (cast_from_oop<intptr_t>(obj) >> 5) & (NINFLATIONLOCKS-1) ; |
6975 | 488 |
int YieldThenBlock = 0 ; |
489 |
assert (ix >= 0 && ix < NINFLATIONLOCKS, "invariant") ; |
|
490 |
assert ((NINFLATIONLOCKS & (NINFLATIONLOCKS-1)) == 0, "invariant") ; |
|
491 |
Thread::muxAcquire (InflationLocks + ix, "InflationLock") ; |
|
492 |
while (obj->mark() == markOopDesc::INFLATING()) { |
|
493 |
// Beware: NakedYield() is advisory and has almost no effect on some platforms |
|
494 |
// so we periodically call Self->_ParkEvent->park(1). |
|
495 |
// We use a mixed spin/yield/block mechanism. |
|
496 |
if ((YieldThenBlock++) >= 16) { |
|
497 |
Thread::current()->_ParkEvent->park(1) ; |
|
498 |
} else { |
|
499 |
os::NakedYield() ; |
|
500 |
} |
|
501 |
} |
|
502 |
Thread::muxRelease (InflationLocks + ix ) ; |
|
503 |
TEVENT (Inflate: INFLATING - yield/park) ; |
|
504 |
} |
|
505 |
} else { |
|
506 |
SpinPause() ; // SMP-polite spinning |
|
507 |
} |
|
508 |
} |
|
509 |
} |
|
1 | 510 |
|
511 |
// hashCode() generation : |
|
512 |
// |
|
513 |
// Possibilities: |
|
514 |
// * MD5Digest of {obj,stwRandom} |
|
515 |
// * CRC32 of {obj,stwRandom} or any linear-feedback shift register function. |
|
516 |
// * A DES- or AES-style SBox[] mechanism |
|
517 |
// * One of the Phi-based schemes, such as: |
|
518 |
// 2654435761 = 2^32 * Phi (golden ratio) |
|
519 |
// HashCodeValue = ((uintptr_t(obj) >> 3) * 2654435761) ^ GVars.stwRandom ; |
|
520 |
// * A variation of Marsaglia's shift-xor RNG scheme. |
|
521 |
// * (obj ^ stwRandom) is appealing, but can result |
|
522 |
// in undesirable regularity in the hashCode values of adjacent objects |
|
523 |
// (objects allocated back-to-back, in particular). This could potentially |
|
524 |
// result in hashtable collisions and reduced hashtable efficiency. |
|
525 |
// There are simple ways to "diffuse" the middle address bits over the |
|
526 |
// generated hashCode values: |
|
527 |
// |
|
528 |
||
529 |
static inline intptr_t get_next_hash(Thread * Self, oop obj) { |
|
530 |
intptr_t value = 0 ; |
|
531 |
if (hashCode == 0) { |
|
532 |
// This form uses an unguarded global Park-Miller RNG, |
|
533 |
// so it's possible for two threads to race and generate the same RNG. |
|
534 |
// On MP system we'll have lots of RW access to a global, so the |
|
535 |
// mechanism induces lots of coherency traffic. |
|
536 |
value = os::random() ; |
|
537 |
} else |
|
538 |
if (hashCode == 1) { |
|
539 |
// This variation has the property of being stable (idempotent) |
|
540 |
// between STW operations. This can be useful in some of the 1-0 |
|
541 |
// synchronization schemes. |
|
20282
7f9cbdf89af2
7195622: CheckUnhandledOops has limited usefulness now
hseigel
parents:
18025
diff
changeset
|
542 |
intptr_t addrBits = cast_from_oop<intptr_t>(obj) >> 3 ; |
1 | 543 |
value = addrBits ^ (addrBits >> 5) ^ GVars.stwRandom ; |
544 |
} else |
|
545 |
if (hashCode == 2) { |
|
546 |
value = 1 ; // for sensitivity testing |
|
547 |
} else |
|
548 |
if (hashCode == 3) { |
|
549 |
value = ++GVars.hcSequence ; |
|
550 |
} else |
|
551 |
if (hashCode == 4) { |
|
20282
7f9cbdf89af2
7195622: CheckUnhandledOops has limited usefulness now
hseigel
parents:
18025
diff
changeset
|
552 |
value = cast_from_oop<intptr_t>(obj) ; |
1 | 553 |
} else { |
554 |
// Marsaglia's xor-shift scheme with thread-specific state |
|
555 |
// This is probably the best overall implementation -- we'll |
|
556 |
// likely make this the default in future releases. |
|
557 |
unsigned t = Self->_hashStateX ; |
|
558 |
t ^= (t << 11) ; |
|
559 |
Self->_hashStateX = Self->_hashStateY ; |
|
560 |
Self->_hashStateY = Self->_hashStateZ ; |
|
561 |
Self->_hashStateZ = Self->_hashStateW ; |
|
562 |
unsigned v = Self->_hashStateW ; |
|
563 |
v = (v ^ (v >> 19)) ^ (t ^ (t >> 8)) ; |
|
564 |
Self->_hashStateW = v ; |
|
565 |
value = v ; |
|
566 |
} |
|
567 |
||
568 |
value &= markOopDesc::hash_mask; |
|
569 |
if (value == 0) value = 0xBAD ; |
|
570 |
assert (value != markOopDesc::no_hash, "invariant") ; |
|
571 |
TEVENT (hashCode: GENERATE) ; |
|
572 |
return value; |
|
573 |
} |
|
6975 | 574 |
// |
575 |
intptr_t ObjectSynchronizer::FastHashCode (Thread * Self, oop obj) { |
|
576 |
if (UseBiasedLocking) { |
|
577 |
// NOTE: many places throughout the JVM do not expect a safepoint |
|
578 |
// to be taken here, in particular most operations on perm gen |
|
579 |
// objects. However, we only ever bias Java instances and all of |
|
580 |
// the call sites of identity_hash that might revoke biases have |
|
581 |
// been checked to make sure they can handle a safepoint. The |
|
582 |
// added check of the bias pattern is to avoid useless calls to |
|
583 |
// thread-local storage. |
|
584 |
if (obj->mark()->has_bias_pattern()) { |
|
585 |
// Box and unbox the raw reference just in case we cause a STW safepoint. |
|
586 |
Handle hobj (Self, obj) ; |
|
587 |
// Relaxing assertion for bug 6320749. |
|
588 |
assert (Universe::verify_in_progress() || |
|
589 |
!SafepointSynchronize::is_at_safepoint(), |
|
590 |
"biases should not be seen by VM thread here"); |
|
591 |
BiasedLocking::revoke_and_rebias(hobj, false, JavaThread::current()); |
|
592 |
obj = hobj() ; |
|
593 |
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
|
594 |
} |
|
595 |
} |
|
1 | 596 |
|
6975 | 597 |
// hashCode() is a heap mutator ... |
598 |
// Relaxing assertion for bug 6320749. |
|
599 |
assert (Universe::verify_in_progress() || |
|
600 |
!SafepointSynchronize::is_at_safepoint(), "invariant") ; |
|
601 |
assert (Universe::verify_in_progress() || |
|
602 |
Self->is_Java_thread() , "invariant") ; |
|
603 |
assert (Universe::verify_in_progress() || |
|
604 |
((JavaThread *)Self)->thread_state() != _thread_blocked, "invariant") ; |
|
605 |
||
606 |
ObjectMonitor* monitor = NULL; |
|
607 |
markOop temp, test; |
|
608 |
intptr_t hash; |
|
609 |
markOop mark = ReadStableMark (obj); |
|
610 |
||
611 |
// object should remain ineligible for biased locking |
|
612 |
assert (!mark->has_bias_pattern(), "invariant") ; |
|
613 |
||
614 |
if (mark->is_neutral()) { |
|
615 |
hash = mark->hash(); // this is a normal header |
|
616 |
if (hash) { // if it has hash, just return it |
|
617 |
return hash; |
|
618 |
} |
|
619 |
hash = get_next_hash(Self, obj); // allocate a new hash code |
|
620 |
temp = mark->copy_set_hash(hash); // merge the hash code into header |
|
621 |
// use (machine word version) atomic operation to install the hash |
|
622 |
test = (markOop) Atomic::cmpxchg_ptr(temp, obj->mark_addr(), mark); |
|
623 |
if (test == mark) { |
|
624 |
return hash; |
|
625 |
} |
|
626 |
// If atomic operation failed, we must inflate the header |
|
627 |
// into heavy weight monitor. We could add more code here |
|
628 |
// for fast path, but it does not worth the complexity. |
|
629 |
} else if (mark->has_monitor()) { |
|
630 |
monitor = mark->monitor(); |
|
631 |
temp = monitor->header(); |
|
632 |
assert (temp->is_neutral(), "invariant") ; |
|
633 |
hash = temp->hash(); |
|
634 |
if (hash) { |
|
635 |
return hash; |
|
636 |
} |
|
637 |
// Skip to the following code to reduce code size |
|
638 |
} else if (Self->is_lock_owned((address)mark->locker())) { |
|
639 |
temp = mark->displaced_mark_helper(); // this is a lightweight monitor owned |
|
640 |
assert (temp->is_neutral(), "invariant") ; |
|
641 |
hash = temp->hash(); // by current thread, check if the displaced |
|
642 |
if (hash) { // header contains hash code |
|
643 |
return hash; |
|
644 |
} |
|
645 |
// WARNING: |
|
646 |
// The displaced header is strictly immutable. |
|
647 |
// It can NOT be changed in ANY cases. So we have |
|
648 |
// to inflate the header into heavyweight monitor |
|
649 |
// even the current thread owns the lock. The reason |
|
650 |
// is the BasicLock (stack slot) will be asynchronously |
|
651 |
// read by other threads during the inflate() function. |
|
652 |
// Any change to stack may not propagate to other threads |
|
653 |
// correctly. |
|
654 |
} |
|
655 |
||
656 |
// Inflate the monitor to set hash code |
|
657 |
monitor = ObjectSynchronizer::inflate(Self, obj); |
|
658 |
// Load displaced header and check it has hash code |
|
659 |
mark = monitor->header(); |
|
660 |
assert (mark->is_neutral(), "invariant") ; |
|
661 |
hash = mark->hash(); |
|
662 |
if (hash == 0) { |
|
663 |
hash = get_next_hash(Self, obj); |
|
664 |
temp = mark->copy_set_hash(hash); // merge hash code into header |
|
665 |
assert (temp->is_neutral(), "invariant") ; |
|
666 |
test = (markOop) Atomic::cmpxchg_ptr(temp, monitor, mark); |
|
667 |
if (test != mark) { |
|
668 |
// The only update to the header in the monitor (outside GC) |
|
669 |
// is install the hash code. If someone add new usage of |
|
670 |
// displaced header, please update this code |
|
671 |
hash = test->hash(); |
|
672 |
assert (test->is_neutral(), "invariant") ; |
|
673 |
assert (hash != 0, "Trivial unexpected object/monitor header usage."); |
|
674 |
} |
|
675 |
} |
|
676 |
// We finally get the hash |
|
677 |
return hash; |
|
1 | 678 |
} |
679 |
||
6975 | 680 |
// Deprecated -- use FastHashCode() instead. |
1 | 681 |
|
6975 | 682 |
intptr_t ObjectSynchronizer::identity_hash_value_for(Handle obj) { |
683 |
return FastHashCode (Thread::current(), obj()) ; |
|
1 | 684 |
} |
685 |
||
686 |
||
6975 | 687 |
bool ObjectSynchronizer::current_thread_holds_lock(JavaThread* thread, |
688 |
Handle h_obj) { |
|
689 |
if (UseBiasedLocking) { |
|
690 |
BiasedLocking::revoke_and_rebias(h_obj, false, thread); |
|
691 |
assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
|
692 |
} |
|
693 |
||
694 |
assert(thread == JavaThread::current(), "Can only be called on current thread"); |
|
695 |
oop obj = h_obj(); |
|
696 |
||
697 |
markOop mark = ReadStableMark (obj) ; |
|
1 | 698 |
|
6975 | 699 |
// Uncontended case, header points to stack |
700 |
if (mark->has_locker()) { |
|
701 |
return thread->is_lock_owned((address)mark->locker()); |
|
1 | 702 |
} |
6975 | 703 |
// Contended case, header points to ObjectMonitor (tagged pointer) |
704 |
if (mark->has_monitor()) { |
|
705 |
ObjectMonitor* monitor = mark->monitor(); |
|
706 |
return monitor->is_entered(thread) != 0 ; |
|
1 | 707 |
} |
6975 | 708 |
// Unlocked case, header in place |
709 |
assert(mark->is_neutral(), "sanity check"); |
|
710 |
return false; |
|
1 | 711 |
} |
712 |
||
6975 | 713 |
// Be aware of this method could revoke bias of the lock object. |
22551 | 714 |
// This method queries the ownership of the lock handle specified by 'h_obj'. |
6975 | 715 |
// If the current thread owns the lock, it returns owner_self. If no |
716 |
// thread owns the lock, it returns owner_none. Otherwise, it will return |
|
22551 | 717 |
// owner_other. |
6975 | 718 |
ObjectSynchronizer::LockOwnership ObjectSynchronizer::query_lock_ownership |
719 |
(JavaThread *self, Handle h_obj) { |
|
720 |
// The caller must beware this method can revoke bias, and |
|
721 |
// revocation can result in a safepoint. |
|
722 |
assert (!SafepointSynchronize::is_at_safepoint(), "invariant") ; |
|
723 |
assert (self->thread_state() != _thread_blocked , "invariant") ; |
|
1 | 724 |
|
6975 | 725 |
// Possible mark states: neutral, biased, stack-locked, inflated |
726 |
||
727 |
if (UseBiasedLocking && h_obj()->mark()->has_bias_pattern()) { |
|
728 |
// CASE: biased |
|
729 |
BiasedLocking::revoke_and_rebias(h_obj, false, self); |
|
730 |
assert(!h_obj->mark()->has_bias_pattern(), |
|
731 |
"biases should be revoked by now"); |
|
732 |
} |
|
1 | 733 |
|
6975 | 734 |
assert(self == JavaThread::current(), "Can only be called on current thread"); |
735 |
oop obj = h_obj(); |
|
736 |
markOop mark = ReadStableMark (obj) ; |
|
737 |
||
738 |
// CASE: stack-locked. Mark points to a BasicLock on the owner's stack. |
|
739 |
if (mark->has_locker()) { |
|
740 |
return self->is_lock_owned((address)mark->locker()) ? |
|
741 |
owner_self : owner_other; |
|
742 |
} |
|
1 | 743 |
|
6975 | 744 |
// CASE: inflated. Mark (tagged pointer) points to an objectMonitor. |
745 |
// The Object:ObjectMonitor relationship is stable as long as we're |
|
746 |
// not at a safepoint. |
|
747 |
if (mark->has_monitor()) { |
|
748 |
void * owner = mark->monitor()->_owner ; |
|
749 |
if (owner == NULL) return owner_none ; |
|
750 |
return (owner == self || |
|
751 |
self->is_lock_owned((address)owner)) ? owner_self : owner_other; |
|
752 |
} |
|
753 |
||
754 |
// CASE: neutral |
|
755 |
assert(mark->is_neutral(), "sanity check"); |
|
756 |
return owner_none ; // it's unlocked |
|
757 |
} |
|
1 | 758 |
|
6975 | 759 |
// FIXME: jvmti should call this |
760 |
JavaThread* ObjectSynchronizer::get_lock_owner(Handle h_obj, bool doLock) { |
|
761 |
if (UseBiasedLocking) { |
|
762 |
if (SafepointSynchronize::is_at_safepoint()) { |
|
763 |
BiasedLocking::revoke_at_safepoint(h_obj); |
|
764 |
} else { |
|
765 |
BiasedLocking::revoke_and_rebias(h_obj, false, JavaThread::current()); |
|
766 |
} |
|
767 |
assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now"); |
|
768 |
} |
|
769 |
||
770 |
oop obj = h_obj(); |
|
771 |
address owner = NULL; |
|
772 |
||
773 |
markOop mark = ReadStableMark (obj) ; |
|
774 |
||
775 |
// Uncontended case, header points to stack |
|
776 |
if (mark->has_locker()) { |
|
777 |
owner = (address) mark->locker(); |
|
778 |
} |
|
779 |
||
780 |
// Contended case, header points to ObjectMonitor (tagged pointer) |
|
781 |
if (mark->has_monitor()) { |
|
782 |
ObjectMonitor* monitor = mark->monitor(); |
|
783 |
assert(monitor != NULL, "monitor should be non-null"); |
|
784 |
owner = (address) monitor->owner(); |
|
785 |
} |
|
786 |
||
787 |
if (owner != NULL) { |
|
15853
1c4e16950e96
8007476: assert(the_owner != NULL) failed: Did not find owning Java thread for lock word address
dcubed
parents:
15475
diff
changeset
|
788 |
// owning_thread_from_monitor_owner() may also return NULL here |
6975 | 789 |
return Threads::owning_thread_from_monitor_owner(owner, doLock); |
790 |
} |
|
791 |
||
792 |
// Unlocked case, header in place |
|
793 |
// Cannot have assertion since this object may have been |
|
794 |
// locked by another thread when reaching here. |
|
795 |
// assert(mark->is_neutral(), "sanity check"); |
|
796 |
||
797 |
return NULL; |
|
798 |
} |
|
799 |
// Visitors ... |
|
800 |
||
801 |
void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure) { |
|
802 |
ObjectMonitor* block = gBlockList; |
|
803 |
ObjectMonitor* mid; |
|
804 |
while (block) { |
|
805 |
assert(block->object() == CHAINMARKER, "must be a block header"); |
|
806 |
for (int i = _BLOCKSIZE - 1; i > 0; i--) { |
|
807 |
mid = block + i; |
|
808 |
oop object = (oop) mid->object(); |
|
809 |
if (object != NULL) { |
|
810 |
closure->do_monitor(mid); |
|
811 |
} |
|
812 |
} |
|
813 |
block = (ObjectMonitor*) block->FreeNext; |
|
1 | 814 |
} |
815 |
} |
|
816 |
||
6975 | 817 |
// Get the next block in the block list. |
818 |
static inline ObjectMonitor* next(ObjectMonitor* block) { |
|
819 |
assert(block->object() == CHAINMARKER, "must be a block header"); |
|
820 |
block = block->FreeNext ; |
|
821 |
assert(block == NULL || block->object() == CHAINMARKER, "must be a block header"); |
|
822 |
return block; |
|
1 | 823 |
} |
824 |
||
825 |
||
6975 | 826 |
void ObjectSynchronizer::oops_do(OopClosure* f) { |
827 |
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); |
|
828 |
for (ObjectMonitor* block = gBlockList; block != NULL; block = next(block)) { |
|
829 |
assert(block->object() == CHAINMARKER, "must be a block header"); |
|
830 |
for (int i = 1; i < _BLOCKSIZE; i++) { |
|
831 |
ObjectMonitor* mid = &block[i]; |
|
832 |
if (mid->object() != NULL) { |
|
833 |
f->do_oop((oop*)mid->object_addr()); |
|
1 | 834 |
} |
835 |
} |
|
836 |
} |
|
837 |
} |
|
838 |
||
839 |
||
6975 | 840 |
// ----------------------------------------------------------------------------- |
1 | 841 |
// ObjectMonitor Lifecycle |
842 |
// ----------------------- |
|
843 |
// Inflation unlinks monitors from the global gFreeList and |
|
844 |
// associates them with objects. Deflation -- which occurs at |
|
845 |
// STW-time -- disassociates idle monitors from objects. Such |
|
846 |
// scavenged monitors are returned to the gFreeList. |
|
847 |
// |
|
848 |
// The global list is protected by ListLock. All the critical sections |
|
849 |
// are short and operate in constant-time. |
|
850 |
// |
|
851 |
// ObjectMonitors reside in type-stable memory (TSM) and are immortal. |
|
852 |
// |
|
853 |
// Lifecycle: |
|
854 |
// -- unassigned and on the global free list |
|
855 |
// -- unassigned and on a thread's private omFreeList |
|
856 |
// -- assigned to an object. The object is inflated and the mark refers |
|
857 |
// to the objectmonitor. |
|
858 |
// |
|
859 |
||
860 |
||
5710 | 861 |
// Constraining monitor pool growth via MonitorBound ... |
862 |
// |
|
863 |
// The monitor pool is grow-only. We scavenge at STW safepoint-time, but the |
|
864 |
// the rate of scavenging is driven primarily by GC. As such, we can find |
|
865 |
// an inordinate number of monitors in circulation. |
|
866 |
// To avoid that scenario we can artificially induce a STW safepoint |
|
867 |
// if the pool appears to be growing past some reasonable bound. |
|
868 |
// Generally we favor time in space-time tradeoffs, but as there's no |
|
869 |
// natural back-pressure on the # of extant monitors we need to impose some |
|
870 |
// type of limit. Beware that if MonitorBound is set to too low a value |
|
871 |
// we could just loop. In addition, if MonitorBound is set to a low value |
|
872 |
// we'll incur more safepoints, which are harmful to performance. |
|
873 |
// See also: GuaranteedSafepointInterval |
|
874 |
// |
|
875 |
// The current implementation uses asynchronous VM operations. |
|
876 |
// |
|
877 |
||
878 |
static void InduceScavenge (Thread * Self, const char * Whence) { |
|
879 |
// Induce STW safepoint to trim monitors |
|
880 |
// Ultimately, this results in a call to deflate_idle_monitors() in the near future. |
|
881 |
// More precisely, trigger an asynchronous STW safepoint as the number |
|
882 |
// of active monitors passes the specified threshold. |
|
883 |
// TODO: assert thread state is reasonable |
|
884 |
||
885 |
if (ForceMonitorScavenge == 0 && Atomic::xchg (1, &ForceMonitorScavenge) == 0) { |
|
6975 | 886 |
if (ObjectMonitor::Knob_Verbose) { |
5710 | 887 |
::printf ("Monitor scavenge - Induced STW @%s (%d)\n", Whence, ForceMonitorScavenge) ; |
888 |
::fflush(stdout) ; |
|
889 |
} |
|
890 |
// Induce a 'null' safepoint to scavenge monitors |
|
891 |
// Must VM_Operation instance be heap allocated as the op will be enqueue and posted |
|
892 |
// to the VMthread and have a lifespan longer than that of this activation record. |
|
893 |
// The VMThread will delete the op when completed. |
|
894 |
VMThread::execute (new VM_ForceAsyncSafepoint()) ; |
|
895 |
||
6975 | 896 |
if (ObjectMonitor::Knob_Verbose) { |
5710 | 897 |
::printf ("Monitor scavenge - STW posted @%s (%d)\n", Whence, ForceMonitorScavenge) ; |
898 |
::fflush(stdout) ; |
|
899 |
} |
|
900 |
} |
|
901 |
} |
|
5920
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
902 |
/* Too slow for general assert or debug |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
903 |
void ObjectSynchronizer::verifyInUse (Thread *Self) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
904 |
ObjectMonitor* mid; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
905 |
int inusetally = 0; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
906 |
for (mid = Self->omInUseList; mid != NULL; mid = mid->FreeNext) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
907 |
inusetally ++; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
908 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
909 |
assert(inusetally == Self->omInUseCount, "inuse count off"); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
910 |
|
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
911 |
int freetally = 0; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
912 |
for (mid = Self->omFreeList; mid != NULL; mid = mid->FreeNext) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
913 |
freetally ++; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
914 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
915 |
assert(freetally == Self->omFreeCount, "free count off"); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
916 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
917 |
*/ |
1 | 918 |
ObjectMonitor * ATTR ObjectSynchronizer::omAlloc (Thread * Self) { |
919 |
// A large MAXPRIVATE value reduces both list lock contention |
|
920 |
// and list coherency traffic, but also tends to increase the |
|
921 |
// number of objectMonitors in circulation as well as the STW |
|
922 |
// scavenge costs. As usual, we lean toward time in space-time |
|
923 |
// tradeoffs. |
|
924 |
const int MAXPRIVATE = 1024 ; |
|
925 |
for (;;) { |
|
926 |
ObjectMonitor * m ; |
|
927 |
||
928 |
// 1: try to allocate from the thread's local omFreeList. |
|
929 |
// Threads will attempt to allocate first from their local list, then |
|
930 |
// from the global list, and only after those attempts fail will the thread |
|
931 |
// attempt to instantiate new monitors. Thread-local free lists take |
|
932 |
// heat off the ListLock and improve allocation latency, as well as reducing |
|
933 |
// coherency traffic on the shared global list. |
|
934 |
m = Self->omFreeList ; |
|
935 |
if (m != NULL) { |
|
936 |
Self->omFreeList = m->FreeNext ; |
|
937 |
Self->omFreeCount -- ; |
|
938 |
// CONSIDER: set m->FreeNext = BAD -- diagnostic hygiene |
|
939 |
guarantee (m->object() == NULL, "invariant") ; |
|
5710 | 940 |
if (MonitorInUseLists) { |
941 |
m->FreeNext = Self->omInUseList; |
|
942 |
Self->omInUseList = m; |
|
943 |
Self->omInUseCount ++; |
|
5920
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
944 |
// verifyInUse(Self); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
945 |
} else { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
946 |
m->FreeNext = NULL; |
5710 | 947 |
} |
1 | 948 |
return m ; |
949 |
} |
|
950 |
||
951 |
// 2: try to allocate from the global gFreeList |
|
952 |
// CONSIDER: use muxTry() instead of muxAcquire(). |
|
953 |
// If the muxTry() fails then drop immediately into case 3. |
|
954 |
// If we're using thread-local free lists then try |
|
955 |
// to reprovision the caller's free list. |
|
956 |
if (gFreeList != NULL) { |
|
957 |
// Reprovision the thread's omFreeList. |
|
958 |
// Use bulk transfers to reduce the allocation rate and heat |
|
959 |
// on various locks. |
|
960 |
Thread::muxAcquire (&ListLock, "omAlloc") ; |
|
961 |
for (int i = Self->omFreeProvision; --i >= 0 && gFreeList != NULL; ) { |
|
5710 | 962 |
MonitorFreeCount --; |
1 | 963 |
ObjectMonitor * take = gFreeList ; |
964 |
gFreeList = take->FreeNext ; |
|
965 |
guarantee (take->object() == NULL, "invariant") ; |
|
966 |
guarantee (!take->is_busy(), "invariant") ; |
|
967 |
take->Recycle() ; |
|
5920
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
968 |
omRelease (Self, take, false) ; |
1 | 969 |
} |
970 |
Thread::muxRelease (&ListLock) ; |
|
971 |
Self->omFreeProvision += 1 + (Self->omFreeProvision/2) ; |
|
972 |
if (Self->omFreeProvision > MAXPRIVATE ) Self->omFreeProvision = MAXPRIVATE ; |
|
973 |
TEVENT (omFirst - reprovision) ; |
|
5710 | 974 |
|
975 |
const int mx = MonitorBound ; |
|
976 |
if (mx > 0 && (MonitorPopulation-MonitorFreeCount) > mx) { |
|
977 |
// We can't safely induce a STW safepoint from omAlloc() as our thread |
|
978 |
// state may not be appropriate for such activities and callers may hold |
|
979 |
// naked oops, so instead we defer the action. |
|
980 |
InduceScavenge (Self, "omAlloc") ; |
|
981 |
} |
|
982 |
continue; |
|
1 | 983 |
} |
984 |
||
985 |
// 3: allocate a block of new ObjectMonitors |
|
986 |
// Both the local and global free lists are empty -- resort to malloc(). |
|
987 |
// In the current implementation objectMonitors are TSM - immortal. |
|
988 |
assert (_BLOCKSIZE > 1, "invariant") ; |
|
17031 | 989 |
ObjectMonitor * temp = new ObjectMonitor[_BLOCKSIZE]; |
1 | 990 |
|
991 |
// NOTE: (almost) no way to recover if allocation failed. |
|
992 |
// We might be able to induce a STW safepoint and scavenge enough |
|
993 |
// objectMonitors to permit progress. |
|
994 |
if (temp == NULL) { |
|
17087
f0b76c4c93a0
8011661: Insufficient memory message says "malloc" when sometimes it should say "mmap"
ccheung
parents:
17031
diff
changeset
|
995 |
vm_exit_out_of_memory (sizeof (ObjectMonitor[_BLOCKSIZE]), OOM_MALLOC_ERROR, |
f0b76c4c93a0
8011661: Insufficient memory message says "malloc" when sometimes it should say "mmap"
ccheung
parents:
17031
diff
changeset
|
996 |
"Allocate ObjectMonitors"); |
1 | 997 |
} |
998 |
||
999 |
// Format the block. |
|
1000 |
// initialize the linked list, each monitor points to its next |
|
1001 |
// forming the single linked free list, the very first monitor |
|
1002 |
// will points to next block, which forms the block list. |
|
1003 |
// The trick of using the 1st element in the block as gBlockList |
|
1004 |
// linkage should be reconsidered. A better implementation would |
|
1005 |
// look like: class Block { Block * next; int N; ObjectMonitor Body [N] ; } |
|
1006 |
||
1007 |
for (int i = 1; i < _BLOCKSIZE ; i++) { |
|
1008 |
temp[i].FreeNext = &temp[i+1]; |
|
1009 |
} |
|
1010 |
||
1011 |
// terminate the last monitor as the end of list |
|
1012 |
temp[_BLOCKSIZE - 1].FreeNext = NULL ; |
|
1013 |
||
1014 |
// Element [0] is reserved for global list linkage |
|
1015 |
temp[0].set_object(CHAINMARKER); |
|
1016 |
||
1017 |
// Consider carving out this thread's current request from the |
|
1018 |
// block in hand. This avoids some lock traffic and redundant |
|
1019 |
// list activity. |
|
1020 |
||
1021 |
// Acquire the ListLock to manipulate BlockList and FreeList. |
|
1022 |
// An Oyama-Taura-Yonezawa scheme might be more efficient. |
|
1023 |
Thread::muxAcquire (&ListLock, "omAlloc [2]") ; |
|
5710 | 1024 |
MonitorPopulation += _BLOCKSIZE-1; |
1025 |
MonitorFreeCount += _BLOCKSIZE-1; |
|
1 | 1026 |
|
1027 |
// Add the new block to the list of extant blocks (gBlockList). |
|
1028 |
// The very first objectMonitor in a block is reserved and dedicated. |
|
1029 |
// It serves as blocklist "next" linkage. |
|
1030 |
temp[0].FreeNext = gBlockList; |
|
1031 |
gBlockList = temp; |
|
1032 |
||
1033 |
// Add the new string of objectMonitors to the global free list |
|
1034 |
temp[_BLOCKSIZE - 1].FreeNext = gFreeList ; |
|
1035 |
gFreeList = temp + 1; |
|
1036 |
Thread::muxRelease (&ListLock) ; |
|
1037 |
TEVENT (Allocate block of monitors) ; |
|
1038 |
} |
|
1039 |
} |
|
1040 |
||
1041 |
// Place "m" on the caller's private per-thread omFreeList. |
|
1042 |
// In practice there's no need to clamp or limit the number of |
|
1043 |
// monitors on a thread's omFreeList as the only time we'll call |
|
1044 |
// omRelease is to return a monitor to the free list after a CAS |
|
1045 |
// attempt failed. This doesn't allow unbounded #s of monitors to |
|
1046 |
// accumulate on a thread's free list. |
|
1047 |
// |
|
1048 |
||
5920
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1049 |
void ObjectSynchronizer::omRelease (Thread * Self, ObjectMonitor * m, bool fromPerThreadAlloc) { |
1 | 1050 |
guarantee (m->object() == NULL, "invariant") ; |
5920
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1051 |
|
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1052 |
// Remove from omInUseList |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1053 |
if (MonitorInUseLists && fromPerThreadAlloc) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1054 |
ObjectMonitor* curmidinuse = NULL; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1055 |
for (ObjectMonitor* mid = Self->omInUseList; mid != NULL; ) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1056 |
if (m == mid) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1057 |
// extract from per-thread in-use-list |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1058 |
if (mid == Self->omInUseList) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1059 |
Self->omInUseList = mid->FreeNext; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1060 |
} else if (curmidinuse != NULL) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1061 |
curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1062 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1063 |
Self->omInUseCount --; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1064 |
// verifyInUse(Self); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1065 |
break; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1066 |
} else { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1067 |
curmidinuse = mid; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1068 |
mid = mid->FreeNext; |
8fdbb85e62d3
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|
1069 |
} |
8fdbb85e62d3
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changeset
|
1070 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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changeset
|
1071 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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diff
changeset
|
1072 |
|
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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changeset
|
1073 |
// FreeNext is used for both onInUseList and omFreeList, so clear old before setting new |
8fdbb85e62d3
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changeset
|
1074 |
m->FreeNext = Self->omFreeList ; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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diff
changeset
|
1075 |
Self->omFreeList = m ; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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changeset
|
1076 |
Self->omFreeCount ++ ; |
1 | 1077 |
} |
1078 |
||
1079 |
// Return the monitors of a moribund thread's local free list to |
|
1080 |
// the global free list. Typically a thread calls omFlush() when |
|
1081 |
// it's dying. We could also consider having the VM thread steal |
|
1082 |
// monitors from threads that have not run java code over a few |
|
1083 |
// consecutive STW safepoints. Relatedly, we might decay |
|
1084 |
// omFreeProvision at STW safepoints. |
|
1085 |
// |
|
5920
8fdbb85e62d3
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|
1086 |
// Also return the monitors of a moribund thread"s omInUseList to |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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changeset
|
1087 |
// a global gOmInUseList under the global list lock so these |
8fdbb85e62d3
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diff
changeset
|
1088 |
// will continue to be scanned. |
8fdbb85e62d3
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changeset
|
1089 |
// |
1 | 1090 |
// We currently call omFlush() from the Thread:: dtor _after the thread |
1091 |
// has been excised from the thread list and is no longer a mutator. |
|
1092 |
// That means that omFlush() can run concurrently with a safepoint and |
|
1093 |
// the scavenge operator. Calling omFlush() from JavaThread::exit() might |
|
1094 |
// be a better choice as we could safely reason that that the JVM is |
|
1095 |
// not at a safepoint at the time of the call, and thus there could |
|
1096 |
// be not inopportune interleavings between omFlush() and the scavenge |
|
1097 |
// operator. |
|
1098 |
||
1099 |
void ObjectSynchronizer::omFlush (Thread * Self) { |
|
1100 |
ObjectMonitor * List = Self->omFreeList ; // Null-terminated SLL |
|
1101 |
Self->omFreeList = NULL ; |
|
1102 |
ObjectMonitor * Tail = NULL ; |
|
5710 | 1103 |
int Tally = 0; |
5920
8fdbb85e62d3
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diff
changeset
|
1104 |
if (List != NULL) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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diff
changeset
|
1105 |
ObjectMonitor * s ; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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changeset
|
1106 |
for (s = List ; s != NULL ; s = s->FreeNext) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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|
1107 |
Tally ++ ; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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diff
changeset
|
1108 |
Tail = s ; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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|
1109 |
guarantee (s->object() == NULL, "invariant") ; |
8fdbb85e62d3
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|
1110 |
guarantee (!s->is_busy(), "invariant") ; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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changeset
|
1111 |
s->set_owner (NULL) ; // redundant but good hygiene |
8fdbb85e62d3
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changeset
|
1112 |
TEVENT (omFlush - Move one) ; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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diff
changeset
|
1113 |
} |
8fdbb85e62d3
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changeset
|
1114 |
guarantee (Tail != NULL && List != NULL, "invariant") ; |
1 | 1115 |
} |
1116 |
||
5920
8fdbb85e62d3
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changeset
|
1117 |
ObjectMonitor * InUseList = Self->omInUseList; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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diff
changeset
|
1118 |
ObjectMonitor * InUseTail = NULL ; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1119 |
int InUseTally = 0; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
5712
diff
changeset
|
1120 |
if (InUseList != NULL) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
5712
diff
changeset
|
1121 |
Self->omInUseList = NULL; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1122 |
ObjectMonitor *curom; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1123 |
for (curom = InUseList; curom != NULL; curom = curom->FreeNext) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1124 |
InUseTail = curom; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1125 |
InUseTally++; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
5712
diff
changeset
|
1126 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1127 |
// TODO debug |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
5712
diff
changeset
|
1128 |
assert(Self->omInUseCount == InUseTally, "inuse count off"); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
5712
diff
changeset
|
1129 |
Self->omInUseCount = 0; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1130 |
guarantee (InUseTail != NULL && InUseList != NULL, "invariant"); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
5712
diff
changeset
|
1131 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
5712
diff
changeset
|
1132 |
|
1 | 1133 |
Thread::muxAcquire (&ListLock, "omFlush") ; |
5920
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
5712
diff
changeset
|
1134 |
if (Tail != NULL) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1135 |
Tail->FreeNext = gFreeList ; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1136 |
gFreeList = List ; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1137 |
MonitorFreeCount += Tally; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1138 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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diff
changeset
|
1139 |
|
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1140 |
if (InUseTail != NULL) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1141 |
InUseTail->FreeNext = gOmInUseList; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1142 |
gOmInUseList = InUseList; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1143 |
gOmInUseCount += InUseTally; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1144 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1145 |
|
1 | 1146 |
Thread::muxRelease (&ListLock) ; |
1147 |
TEVENT (omFlush) ; |
|
1148 |
} |
|
1149 |
||
1150 |
// Fast path code shared by multiple functions |
|
1151 |
ObjectMonitor* ObjectSynchronizer::inflate_helper(oop obj) { |
|
1152 |
markOop mark = obj->mark(); |
|
1153 |
if (mark->has_monitor()) { |
|
1154 |
assert(ObjectSynchronizer::verify_objmon_isinpool(mark->monitor()), "monitor is invalid"); |
|
1155 |
assert(mark->monitor()->header()->is_neutral(), "monitor must record a good object header"); |
|
1156 |
return mark->monitor(); |
|
1157 |
} |
|
1158 |
return ObjectSynchronizer::inflate(Thread::current(), obj); |
|
1159 |
} |
|
1160 |
||
6975 | 1161 |
|
1 | 1162 |
// Note that we could encounter some performance loss through false-sharing as |
1163 |
// multiple locks occupy the same $ line. Padding might be appropriate. |
|
1164 |
||
1165 |
||
1166 |
ObjectMonitor * ATTR ObjectSynchronizer::inflate (Thread * Self, oop object) { |
|
1167 |
// Inflate mutates the heap ... |
|
1168 |
// Relaxing assertion for bug 6320749. |
|
1169 |
assert (Universe::verify_in_progress() || |
|
1170 |
!SafepointSynchronize::is_at_safepoint(), "invariant") ; |
|
1171 |
||
1172 |
for (;;) { |
|
1173 |
const markOop mark = object->mark() ; |
|
1174 |
assert (!mark->has_bias_pattern(), "invariant") ; |
|
1175 |
||
1176 |
// The mark can be in one of the following states: |
|
1177 |
// * Inflated - just return |
|
1178 |
// * Stack-locked - coerce it to inflated |
|
1179 |
// * INFLATING - busy wait for conversion to complete |
|
1180 |
// * Neutral - aggressively inflate the object. |
|
1181 |
// * BIASED - Illegal. We should never see this |
|
1182 |
||
1183 |
// CASE: inflated |
|
1184 |
if (mark->has_monitor()) { |
|
1185 |
ObjectMonitor * inf = mark->monitor() ; |
|
1186 |
assert (inf->header()->is_neutral(), "invariant"); |
|
1187 |
assert (inf->object() == object, "invariant") ; |
|
1188 |
assert (ObjectSynchronizer::verify_objmon_isinpool(inf), "monitor is invalid"); |
|
1189 |
return inf ; |
|
1190 |
} |
|
1191 |
||
1192 |
// CASE: inflation in progress - inflating over a stack-lock. |
|
1193 |
// Some other thread is converting from stack-locked to inflated. |
|
1194 |
// Only that thread can complete inflation -- other threads must wait. |
|
1195 |
// The INFLATING value is transient. |
|
1196 |
// Currently, we spin/yield/park and poll the markword, waiting for inflation to finish. |
|
1197 |
// We could always eliminate polling by parking the thread on some auxiliary list. |
|
1198 |
if (mark == markOopDesc::INFLATING()) { |
|
1199 |
TEVENT (Inflate: spin while INFLATING) ; |
|
1200 |
ReadStableMark(object) ; |
|
1201 |
continue ; |
|
1202 |
} |
|
1203 |
||
1204 |
// CASE: stack-locked |
|
1205 |
// Could be stack-locked either by this thread or by some other thread. |
|
1206 |
// |
|
1207 |
// Note that we allocate the objectmonitor speculatively, _before_ attempting |
|
1208 |
// to install INFLATING into the mark word. We originally installed INFLATING, |
|
1209 |
// allocated the objectmonitor, and then finally STed the address of the |
|
1210 |
// objectmonitor into the mark. This was correct, but artificially lengthened |
|
1211 |
// the interval in which INFLATED appeared in the mark, thus increasing |
|
1212 |
// the odds of inflation contention. |
|
1213 |
// |
|
1214 |
// We now use per-thread private objectmonitor free lists. |
|
1215 |
// These list are reprovisioned from the global free list outside the |
|
1216 |
// critical INFLATING...ST interval. A thread can transfer |
|
1217 |
// multiple objectmonitors en-mass from the global free list to its local free list. |
|
1218 |
// This reduces coherency traffic and lock contention on the global free list. |
|
1219 |
// Using such local free lists, it doesn't matter if the omAlloc() call appears |
|
1220 |
// before or after the CAS(INFLATING) operation. |
|
1221 |
// See the comments in omAlloc(). |
|
1222 |
||
1223 |
if (mark->has_locker()) { |
|
1224 |
ObjectMonitor * m = omAlloc (Self) ; |
|
1225 |
// Optimistically prepare the objectmonitor - anticipate successful CAS |
|
1226 |
// We do this before the CAS in order to minimize the length of time |
|
1227 |
// in which INFLATING appears in the mark. |
|
1228 |
m->Recycle(); |
|
1229 |
m->_Responsible = NULL ; |
|
1230 |
m->OwnerIsThread = 0 ; |
|
1231 |
m->_recursions = 0 ; |
|
6975 | 1232 |
m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ; // Consider: maintain by type/class |
1 | 1233 |
|
1234 |
markOop cmp = (markOop) Atomic::cmpxchg_ptr (markOopDesc::INFLATING(), object->mark_addr(), mark) ; |
|
1235 |
if (cmp != mark) { |
|
5920
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diff
changeset
|
1236 |
omRelease (Self, m, true) ; |
1 | 1237 |
continue ; // Interference -- just retry |
1238 |
} |
|
1239 |
||
1240 |
// We've successfully installed INFLATING (0) into the mark-word. |
|
1241 |
// This is the only case where 0 will appear in a mark-work. |
|
1242 |
// Only the singular thread that successfully swings the mark-word |
|
1243 |
// to 0 can perform (or more precisely, complete) inflation. |
|
1244 |
// |
|
1245 |
// Why do we CAS a 0 into the mark-word instead of just CASing the |
|
1246 |
// mark-word from the stack-locked value directly to the new inflated state? |
|
1247 |
// Consider what happens when a thread unlocks a stack-locked object. |
|
1248 |
// It attempts to use CAS to swing the displaced header value from the |
|
1249 |
// on-stack basiclock back into the object header. Recall also that the |
|
1250 |
// header value (hashcode, etc) can reside in (a) the object header, or |
|
1251 |
// (b) a displaced header associated with the stack-lock, or (c) a displaced |
|
1252 |
// header in an objectMonitor. The inflate() routine must copy the header |
|
1253 |
// value from the basiclock on the owner's stack to the objectMonitor, all |
|
1254 |
// the while preserving the hashCode stability invariants. If the owner |
|
1255 |
// decides to release the lock while the value is 0, the unlock will fail |
|
1256 |
// and control will eventually pass from slow_exit() to inflate. The owner |
|
1257 |
// will then spin, waiting for the 0 value to disappear. Put another way, |
|
1258 |
// the 0 causes the owner to stall if the owner happens to try to |
|
1259 |
// drop the lock (restoring the header from the basiclock to the object) |
|
1260 |
// while inflation is in-progress. This protocol avoids races that might |
|
1261 |
// would otherwise permit hashCode values to change or "flicker" for an object. |
|
1262 |
// Critically, while object->mark is 0 mark->displaced_mark_helper() is stable. |
|
1263 |
// 0 serves as a "BUSY" inflate-in-progress indicator. |
|
1264 |
||
1265 |
||
1266 |
// fetch the displaced mark from the owner's stack. |
|
1267 |
// The owner can't die or unwind past the lock while our INFLATING |
|
1268 |
// object is in the mark. Furthermore the owner can't complete |
|
1269 |
// an unlock on the object, either. |
|
1270 |
markOop dmw = mark->displaced_mark_helper() ; |
|
1271 |
assert (dmw->is_neutral(), "invariant") ; |
|
1272 |
||
1273 |
// Setup monitor fields to proper values -- prepare the monitor |
|
1274 |
m->set_header(dmw) ; |
|
1275 |
||
1276 |
// Optimization: if the mark->locker stack address is associated |
|
1277 |
// with this thread we could simply set m->_owner = Self and |
|
2526
39a58a50be35
6699669: Hotspot server leaves synchronized block with monitor in bad state
xlu
parents:
2105
diff
changeset
|
1278 |
// m->OwnerIsThread = 1. Note that a thread can inflate an object |
1 | 1279 |
// that it has stack-locked -- as might happen in wait() -- directly |
1280 |
// with CAS. That is, we can avoid the xchg-NULL .... ST idiom. |
|
2526
39a58a50be35
6699669: Hotspot server leaves synchronized block with monitor in bad state
xlu
parents:
2105
diff
changeset
|
1281 |
m->set_owner(mark->locker()); |
1 | 1282 |
m->set_object(object); |
1283 |
// TODO-FIXME: assert BasicLock->dhw != 0. |
|
1284 |
||
1285 |
// Must preserve store ordering. The monitor state must |
|
1286 |
// be stable at the time of publishing the monitor address. |
|
1287 |
guarantee (object->mark() == markOopDesc::INFLATING(), "invariant") ; |
|
1288 |
object->release_set_mark(markOopDesc::encode(m)); |
|
1289 |
||
1290 |
// Hopefully the performance counters are allocated on distinct cache lines |
|
1291 |
// to avoid false sharing on MP systems ... |
|
6975 | 1292 |
if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ; |
1 | 1293 |
TEVENT(Inflate: overwrite stacklock) ; |
1294 |
if (TraceMonitorInflation) { |
|
1295 |
if (object->is_instance()) { |
|
1296 |
ResourceMark rm; |
|
1297 |
tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", |
|
20282
7f9cbdf89af2
7195622: CheckUnhandledOops has limited usefulness now
hseigel
parents:
18025
diff
changeset
|
1298 |
(void *) object, (intptr_t) object->mark(), |
14488 | 1299 |
object->klass()->external_name()); |
1 | 1300 |
} |
1301 |
} |
|
1302 |
return m ; |
|
1303 |
} |
|
1304 |
||
1305 |
// CASE: neutral |
|
1306 |
// TODO-FIXME: for entry we currently inflate and then try to CAS _owner. |
|
1307 |
// If we know we're inflating for entry it's better to inflate by swinging a |
|
1308 |
// pre-locked objectMonitor pointer into the object header. A successful |
|
1309 |
// CAS inflates the object *and* confers ownership to the inflating thread. |
|
1310 |
// In the current implementation we use a 2-step mechanism where we CAS() |
|
1311 |
// to inflate and then CAS() again to try to swing _owner from NULL to Self. |
|
1312 |
// An inflateTry() method that we could call from fast_enter() and slow_enter() |
|
1313 |
// would be useful. |
|
1314 |
||
1315 |
assert (mark->is_neutral(), "invariant"); |
|
1316 |
ObjectMonitor * m = omAlloc (Self) ; |
|
1317 |
// prepare m for installation - set monitor to initial state |
|
1318 |
m->Recycle(); |
|
1319 |
m->set_header(mark); |
|
1320 |
m->set_owner(NULL); |
|
1321 |
m->set_object(object); |
|
1322 |
m->OwnerIsThread = 1 ; |
|
1323 |
m->_recursions = 0 ; |
|
1324 |
m->_Responsible = NULL ; |
|
6975 | 1325 |
m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ; // consider: keep metastats by type/class |
1 | 1326 |
|
1327 |
if (Atomic::cmpxchg_ptr (markOopDesc::encode(m), object->mark_addr(), mark) != mark) { |
|
1328 |
m->set_object (NULL) ; |
|
1329 |
m->set_owner (NULL) ; |
|
1330 |
m->OwnerIsThread = 0 ; |
|
1331 |
m->Recycle() ; |
|
5920
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diff
changeset
|
1332 |
omRelease (Self, m, true) ; |
1 | 1333 |
m = NULL ; |
1334 |
continue ; |
|
1335 |
// interference - the markword changed - just retry. |
|
1336 |
// The state-transitions are one-way, so there's no chance of |
|
1337 |
// live-lock -- "Inflated" is an absorbing state. |
|
1338 |
} |
|
1339 |
||
1340 |
// Hopefully the performance counters are allocated on distinct |
|
1341 |
// cache lines to avoid false sharing on MP systems ... |
|
6975 | 1342 |
if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ; |
1 | 1343 |
TEVENT(Inflate: overwrite neutral) ; |
1344 |
if (TraceMonitorInflation) { |
|
1345 |
if (object->is_instance()) { |
|
1346 |
ResourceMark rm; |
|
1347 |
tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", |
|
20282
7f9cbdf89af2
7195622: CheckUnhandledOops has limited usefulness now
hseigel
parents:
18025
diff
changeset
|
1348 |
(void *) object, (intptr_t) object->mark(), |
14488 | 1349 |
object->klass()->external_name()); |
1 | 1350 |
} |
1351 |
} |
|
1352 |
return m ; |
|
1353 |
} |
|
1354 |
} |
|
1355 |
||
6975 | 1356 |
// Note that we could encounter some performance loss through false-sharing as |
1357 |
// multiple locks occupy the same $ line. Padding might be appropriate. |
|
1 | 1358 |
|
1359 |
||
1360 |
// Deflate_idle_monitors() is called at all safepoints, immediately |
|
1361 |
// after all mutators are stopped, but before any objects have moved. |
|
1362 |
// It traverses the list of known monitors, deflating where possible. |
|
1363 |
// The scavenged monitor are returned to the monitor free list. |
|
1364 |
// |
|
1365 |
// Beware that we scavenge at *every* stop-the-world point. |
|
1366 |
// Having a large number of monitors in-circulation negatively |
|
1367 |
// impacts the performance of some applications (e.g., PointBase). |
|
1368 |
// Broadly, we want to minimize the # of monitors in circulation. |
|
5710 | 1369 |
// |
1370 |
// We have added a flag, MonitorInUseLists, which creates a list |
|
1371 |
// of active monitors for each thread. deflate_idle_monitors() |
|
1372 |
// only scans the per-thread inuse lists. omAlloc() puts all |
|
1373 |
// assigned monitors on the per-thread list. deflate_idle_monitors() |
|
1374 |
// returns the non-busy monitors to the global free list. |
|
5920
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diff
changeset
|
1375 |
// When a thread dies, omFlush() adds the list of active monitors for |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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changeset
|
1376 |
// that thread to a global gOmInUseList acquiring the |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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diff
changeset
|
1377 |
// global list lock. deflate_idle_monitors() acquires the global |
8fdbb85e62d3
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diff
changeset
|
1378 |
// list lock to scan for non-busy monitors to the global free list. |
5710 | 1379 |
// An alternative could have used a single global inuse list. The |
1380 |
// downside would have been the additional cost of acquiring the global list lock |
|
1381 |
// for every omAlloc(). |
|
1 | 1382 |
// |
1383 |
// Perversely, the heap size -- and thus the STW safepoint rate -- |
|
1384 |
// typically drives the scavenge rate. Large heaps can mean infrequent GC, |
|
1385 |
// which in turn can mean large(r) numbers of objectmonitors in circulation. |
|
1386 |
// This is an unfortunate aspect of this design. |
|
1387 |
// |
|
1388 |
||
6975 | 1389 |
enum ManifestConstants { |
1390 |
ClearResponsibleAtSTW = 0, |
|
1391 |
MaximumRecheckInterval = 1000 |
|
1392 |
} ; |
|
5710 | 1393 |
|
1394 |
// Deflate a single monitor if not in use |
|
1395 |
// Return true if deflated, false if in use |
|
1396 |
bool ObjectSynchronizer::deflate_monitor(ObjectMonitor* mid, oop obj, |
|
1397 |
ObjectMonitor** FreeHeadp, ObjectMonitor** FreeTailp) { |
|
1398 |
bool deflated; |
|
1399 |
// Normal case ... The monitor is associated with obj. |
|
1400 |
guarantee (obj->mark() == markOopDesc::encode(mid), "invariant") ; |
|
1401 |
guarantee (mid == obj->mark()->monitor(), "invariant"); |
|
1402 |
guarantee (mid->header()->is_neutral(), "invariant"); |
|
1403 |
||
1404 |
if (mid->is_busy()) { |
|
1405 |
if (ClearResponsibleAtSTW) mid->_Responsible = NULL ; |
|
1406 |
deflated = false; |
|
1407 |
} else { |
|
1408 |
// Deflate the monitor if it is no longer being used |
|
1409 |
// It's idle - scavenge and return to the global free list |
|
1410 |
// plain old deflation ... |
|
1411 |
TEVENT (deflate_idle_monitors - scavenge1) ; |
|
1412 |
if (TraceMonitorInflation) { |
|
1413 |
if (obj->is_instance()) { |
|
1414 |
ResourceMark rm; |
|
1415 |
tty->print_cr("Deflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", |
|
20282
7f9cbdf89af2
7195622: CheckUnhandledOops has limited usefulness now
hseigel
parents:
18025
diff
changeset
|
1416 |
(void *) obj, (intptr_t) obj->mark(), obj->klass()->external_name()); |
5710 | 1417 |
} |
1418 |
} |
|
1419 |
||
1420 |
// Restore the header back to obj |
|
1421 |
obj->release_set_mark(mid->header()); |
|
1422 |
mid->clear(); |
|
1423 |
||
1424 |
assert (mid->object() == NULL, "invariant") ; |
|
1425 |
||
1426 |
// Move the object to the working free list defined by FreeHead,FreeTail. |
|
1427 |
if (*FreeHeadp == NULL) *FreeHeadp = mid; |
|
1428 |
if (*FreeTailp != NULL) { |
|
1429 |
ObjectMonitor * prevtail = *FreeTailp; |
|
5920
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1430 |
assert(prevtail->FreeNext == NULL, "cleaned up deflated?"); // TODO KK |
5710 | 1431 |
prevtail->FreeNext = mid; |
1432 |
} |
|
1433 |
*FreeTailp = mid; |
|
1434 |
deflated = true; |
|
1435 |
} |
|
1436 |
return deflated; |
|
1437 |
} |
|
1438 |
||
5920
8fdbb85e62d3
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parents:
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diff
changeset
|
1439 |
// Caller acquires ListLock |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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parents:
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diff
changeset
|
1440 |
int ObjectSynchronizer::walk_monitor_list(ObjectMonitor** listheadp, |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
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diff
changeset
|
1441 |
ObjectMonitor** FreeHeadp, ObjectMonitor** FreeTailp) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
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diff
changeset
|
1442 |
ObjectMonitor* mid; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1443 |
ObjectMonitor* next; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1444 |
ObjectMonitor* curmidinuse = NULL; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1445 |
int deflatedcount = 0; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1446 |
|
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
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diff
changeset
|
1447 |
for (mid = *listheadp; mid != NULL; ) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1448 |
oop obj = (oop) mid->object(); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1449 |
bool deflated = false; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1450 |
if (obj != NULL) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1451 |
deflated = deflate_monitor(mid, obj, FreeHeadp, FreeTailp); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1452 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1453 |
if (deflated) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
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diff
changeset
|
1454 |
// extract from per-thread in-use-list |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1455 |
if (mid == *listheadp) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1456 |
*listheadp = mid->FreeNext; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1457 |
} else if (curmidinuse != NULL) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1458 |
curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1459 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1460 |
next = mid->FreeNext; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1461 |
mid->FreeNext = NULL; // This mid is current tail in the FreeHead list |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1462 |
mid = next; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1463 |
deflatedcount++; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1464 |
} else { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1465 |
curmidinuse = mid; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1466 |
mid = mid->FreeNext; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1467 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1468 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1469 |
return deflatedcount; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1470 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1471 |
|
1 | 1472 |
void ObjectSynchronizer::deflate_idle_monitors() { |
1473 |
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); |
|
1474 |
int nInuse = 0 ; // currently associated with objects |
|
1475 |
int nInCirculation = 0 ; // extant |
|
1476 |
int nScavenged = 0 ; // reclaimed |
|
5710 | 1477 |
bool deflated = false; |
1 | 1478 |
|
1479 |
ObjectMonitor * FreeHead = NULL ; // Local SLL of scavenged monitors |
|
1480 |
ObjectMonitor * FreeTail = NULL ; |
|
1481 |
||
5710 | 1482 |
TEVENT (deflate_idle_monitors) ; |
1483 |
// Prevent omFlush from changing mids in Thread dtor's during deflation |
|
1484 |
// And in case the vm thread is acquiring a lock during a safepoint |
|
1485 |
// See e.g. 6320749 |
|
1486 |
Thread::muxAcquire (&ListLock, "scavenge - return") ; |
|
1487 |
||
1488 |
if (MonitorInUseLists) { |
|
5920
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1489 |
int inUse = 0; |
5710 | 1490 |
for (JavaThread* cur = Threads::first(); cur != NULL; cur = cur->next()) { |
5920
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1491 |
nInCirculation+= cur->omInUseCount; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1492 |
int deflatedcount = walk_monitor_list(cur->omInUseList_addr(), &FreeHead, &FreeTail); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1493 |
cur->omInUseCount-= deflatedcount; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1494 |
// verifyInUse(cur); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1495 |
nScavenged += deflatedcount; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1496 |
nInuse += cur->omInUseCount; |
5710 | 1497 |
} |
5920
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1498 |
|
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1499 |
// For moribund threads, scan gOmInUseList |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1500 |
if (gOmInUseList) { |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1501 |
nInCirculation += gOmInUseCount; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1502 |
int deflatedcount = walk_monitor_list((ObjectMonitor **)&gOmInUseList, &FreeHead, &FreeTail); |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1503 |
gOmInUseCount-= deflatedcount; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1504 |
nScavenged += deflatedcount; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1505 |
nInuse += gOmInUseCount; |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1506 |
} |
8fdbb85e62d3
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
5712
diff
changeset
|
1507 |
|
5710 | 1508 |
} else for (ObjectMonitor* block = gBlockList; block != NULL; block = next(block)) { |
1 | 1509 |
// Iterate over all extant monitors - Scavenge all idle monitors. |
1510 |
assert(block->object() == CHAINMARKER, "must be a block header"); |
|
1511 |
nInCirculation += _BLOCKSIZE ; |
|
1512 |
for (int i = 1 ; i < _BLOCKSIZE; i++) { |
|
1513 |
ObjectMonitor* mid = &block[i]; |
|
1514 |
oop obj = (oop) mid->object(); |
|
1515 |
||
1516 |
if (obj == NULL) { |
|
1517 |
// The monitor is not associated with an object. |
|
1518 |
// The monitor should either be a thread-specific private |
|
1519 |
// free list or the global free list. |
|
1520 |
// obj == NULL IMPLIES mid->is_busy() == 0 |
|
1521 |
guarantee (!mid->is_busy(), "invariant") ; |
|
1522 |
continue ; |
|
1523 |
} |
|
5710 | 1524 |
deflated = deflate_monitor(mid, obj, &FreeHead, &FreeTail); |
1525 |
||
1526 |
if (deflated) { |
|
1527 |
mid->FreeNext = NULL ; |
|
1528 |
nScavenged ++ ; |
|
1 | 1529 |
} else { |
5710 | 1530 |
nInuse ++; |
1 | 1531 |
} |
1532 |
} |
|
1533 |
} |
|
1534 |
||
5710 | 1535 |
MonitorFreeCount += nScavenged; |
1536 |
||
1537 |
// Consider: audit gFreeList to ensure that MonitorFreeCount and list agree. |
|
1538 |
||
6975 | 1539 |
if (ObjectMonitor::Knob_Verbose) { |
5710 | 1540 |
::printf ("Deflate: InCirc=%d InUse=%d Scavenged=%d ForceMonitorScavenge=%d : pop=%d free=%d\n", |
1541 |
nInCirculation, nInuse, nScavenged, ForceMonitorScavenge, |
|
1542 |
MonitorPopulation, MonitorFreeCount) ; |
|
1543 |
::fflush(stdout) ; |
|
1544 |
} |
|
1545 |
||
1546 |
ForceMonitorScavenge = 0; // Reset |
|
1547 |
||
1 | 1548 |
// Move the scavenged monitors back to the global free list. |
1549 |
if (FreeHead != NULL) { |
|
1550 |
guarantee (FreeTail != NULL && nScavenged > 0, "invariant") ; |
|
1551 |
assert (FreeTail->FreeNext == NULL, "invariant") ; |
|
1552 |
// constant-time list splice - prepend scavenged segment to gFreeList |
|
1553 |
FreeTail->FreeNext = gFreeList ; |
|
1554 |
gFreeList = FreeHead ; |
|
1555 |
} |
|
5710 | 1556 |
Thread::muxRelease (&ListLock) ; |
1 | 1557 |
|
6975 | 1558 |
if (ObjectMonitor::_sync_Deflations != NULL) ObjectMonitor::_sync_Deflations->inc(nScavenged) ; |
1559 |
if (ObjectMonitor::_sync_MonExtant != NULL) ObjectMonitor::_sync_MonExtant ->set_value(nInCirculation); |
|
1 | 1560 |
|
1561 |
// TODO: Add objectMonitor leak detection. |
|
1562 |
// Audit/inventory the objectMonitors -- make sure they're all accounted for. |
|
1563 |
GVars.stwRandom = os::random() ; |
|
1564 |
GVars.stwCycle ++ ; |
|
1565 |
} |
|
1566 |
||
6975 | 1567 |
// Monitor cleanup on JavaThread::exit |
1 | 1568 |
|
6975 | 1569 |
// Iterate through monitor cache and attempt to release thread's monitors |
1570 |
// Gives up on a particular monitor if an exception occurs, but continues |
|
1571 |
// the overall iteration, swallowing the exception. |
|
1572 |
class ReleaseJavaMonitorsClosure: public MonitorClosure { |
|
1573 |
private: |
|
1574 |
TRAPS; |
|
1 | 1575 |
|
6975 | 1576 |
public: |
1577 |
ReleaseJavaMonitorsClosure(Thread* thread) : THREAD(thread) {} |
|
1578 |
void do_monitor(ObjectMonitor* mid) { |
|
1579 |
if (mid->owner() == THREAD) { |
|
1580 |
(void)mid->complete_exit(CHECK); |
|
1 | 1581 |
} |
1582 |
} |
|
6975 | 1583 |
}; |
1 | 1584 |
|
6975 | 1585 |
// Release all inflated monitors owned by THREAD. Lightweight monitors are |
1586 |
// ignored. This is meant to be called during JNI thread detach which assumes |
|
1587 |
// all remaining monitors are heavyweight. All exceptions are swallowed. |
|
1588 |
// Scanning the extant monitor list can be time consuming. |
|
1589 |
// A simple optimization is to add a per-thread flag that indicates a thread |
|
1590 |
// called jni_monitorenter() during its lifetime. |
|
1 | 1591 |
// |
6975 | 1592 |
// Instead of No_Savepoint_Verifier it might be cheaper to |
1593 |
// use an idiom of the form: |
|
1594 |
// auto int tmp = SafepointSynchronize::_safepoint_counter ; |
|
1595 |
// <code that must not run at safepoint> |
|
1596 |
// guarantee (((tmp ^ _safepoint_counter) | (tmp & 1)) == 0) ; |
|
1597 |
// Since the tests are extremely cheap we could leave them enabled |
|
1598 |
// for normal product builds. |
|
1 | 1599 |
|
6975 | 1600 |
void ObjectSynchronizer::release_monitors_owned_by_thread(TRAPS) { |
1601 |
assert(THREAD == JavaThread::current(), "must be current Java thread"); |
|
1602 |
No_Safepoint_Verifier nsv ; |
|
1603 |
ReleaseJavaMonitorsClosure rjmc(THREAD); |
|
1604 |
Thread::muxAcquire(&ListLock, "release_monitors_owned_by_thread"); |
|
1605 |
ObjectSynchronizer::monitors_iterate(&rjmc); |
|
1606 |
Thread::muxRelease(&ListLock); |
|
1607 |
THREAD->clear_pending_exception(); |
|
1 | 1608 |
} |
1609 |
||
1610 |
//------------------------------------------------------------------------------ |
|
1611 |
// Non-product code |
|
1612 |
||
1613 |
#ifndef PRODUCT |
|
1614 |
||
1615 |
// Verify all monitors in the monitor cache, the verification is weak. |
|
1616 |
void ObjectSynchronizer::verify() { |
|
1617 |
ObjectMonitor* block = gBlockList; |
|
1618 |
ObjectMonitor* mid; |
|
1619 |
while (block) { |
|
1620 |
assert(block->object() == CHAINMARKER, "must be a block header"); |
|
1621 |
for (int i = 1; i < _BLOCKSIZE; i++) { |
|
1622 |
mid = block + i; |
|
1623 |
oop object = (oop) mid->object(); |
|
1624 |
if (object != NULL) { |
|
1625 |
mid->verify(); |
|
1626 |
} |
|
1627 |
} |
|
1628 |
block = (ObjectMonitor*) block->FreeNext; |
|
1629 |
} |
|
1630 |
} |
|
1631 |
||
1632 |
// Check if monitor belongs to the monitor cache |
|
1633 |
// The list is grow-only so it's *relatively* safe to traverse |
|
1634 |
// the list of extant blocks without taking a lock. |
|
1635 |
||
1636 |
int ObjectSynchronizer::verify_objmon_isinpool(ObjectMonitor *monitor) { |
|
1637 |
ObjectMonitor* block = gBlockList; |
|
1638 |
||
1639 |
while (block) { |
|
1640 |
assert(block->object() == CHAINMARKER, "must be a block header"); |
|
1641 |
if (monitor > &block[0] && monitor < &block[_BLOCKSIZE]) { |
|
1642 |
address mon = (address) monitor; |
|
1643 |
address blk = (address) block; |
|
1644 |
size_t diff = mon - blk; |
|
1645 |
assert((diff % sizeof(ObjectMonitor)) == 0, "check"); |
|
1646 |
return 1; |
|
1647 |
} |
|
1648 |
block = (ObjectMonitor*) block->FreeNext; |
|
1649 |
} |
|
1650 |
return 0; |
|
1651 |
} |
|
1652 |
||
1653 |
#endif |