--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.cpp Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,350 @@
+/*
+ * Copyright 2001-2006 Sun Microsystems, Inc. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+# include "incls/_precompiled.incl"
+# include "incls/_concurrentMarkSweepThread.cpp.incl"
+
+// ======= Concurrent Mark Sweep Thread ========
+
+// The CMS thread is created when Concurrent Mark Sweep is used in the
+// older of two generations in a generational memory system.
+
+ConcurrentMarkSweepThread*
+ ConcurrentMarkSweepThread::_cmst = NULL;
+CMSCollector* ConcurrentMarkSweepThread::_collector = NULL;
+bool ConcurrentMarkSweepThread::_should_terminate = false;
+int ConcurrentMarkSweepThread::_CMS_flag = CMS_nil;
+
+volatile jint ConcurrentMarkSweepThread::_pending_yields = 0;
+volatile jint ConcurrentMarkSweepThread::_pending_decrements = 0;
+
+volatile bool ConcurrentMarkSweepThread::_icms_enabled = false;
+volatile bool ConcurrentMarkSweepThread::_should_run = false;
+// When icms is enabled, the icms thread is stopped until explicitly
+// started.
+volatile bool ConcurrentMarkSweepThread::_should_stop = true;
+
+SurrogateLockerThread*
+ ConcurrentMarkSweepThread::_slt = NULL;
+SurrogateLockerThread::SLT_msg_type
+ ConcurrentMarkSweepThread::_sltBuffer = SurrogateLockerThread::empty;
+Monitor*
+ ConcurrentMarkSweepThread::_sltMonitor = NULL;
+
+ConcurrentMarkSweepThread::ConcurrentMarkSweepThread(CMSCollector* collector)
+ : ConcurrentGCThread() {
+ assert(UseConcMarkSweepGC, "UseConcMarkSweepGC should be set");
+ assert(_cmst == NULL, "CMS thread already created");
+ _cmst = this;
+ assert(_collector == NULL, "Collector already set");
+ _collector = collector;
+
+ set_name("Concurrent Mark-Sweep GC Thread");
+
+ if (os::create_thread(this, os::cgc_thread)) {
+ // XXX: need to set this to low priority
+ // unless "agressive mode" set; priority
+ // should be just less than that of VMThread.
+ os::set_priority(this, NearMaxPriority);
+ if (!DisableStartThread) {
+ os::start_thread(this);
+ }
+ }
+ _sltMonitor = SLT_lock;
+ set_icms_enabled(CMSIncrementalMode);
+}
+
+void ConcurrentMarkSweepThread::run() {
+ assert(this == cmst(), "just checking");
+
+ this->record_stack_base_and_size();
+ this->initialize_thread_local_storage();
+ this->set_active_handles(JNIHandleBlock::allocate_block());
+ // From this time Thread::current() should be working.
+ assert(this == Thread::current(), "just checking");
+ if (BindCMSThreadToCPU && !os::bind_to_processor(CPUForCMSThread)) {
+ warning("Couldn't bind CMS thread to processor %u", CPUForCMSThread);
+ }
+ // Wait until Universe::is_fully_initialized()
+ {
+ CMSLoopCountWarn loopX("CMS::run", "waiting for "
+ "Universe::is_fully_initialized()", 2);
+ MutexLockerEx x(CGC_lock, true);
+ set_CMS_flag(CMS_cms_wants_token);
+ // Wait until Universe is initialized and all initialization is completed.
+ while (!is_init_completed() && !Universe::is_fully_initialized() &&
+ !_should_terminate) {
+ CGC_lock->wait(true, 200);
+ loopX.tick();
+ }
+ // Wait until the surrogate locker thread that will do
+ // pending list locking on our behalf has been created.
+ // We cannot start the SLT thread ourselves since we need
+ // to be a JavaThread to do so.
+ CMSLoopCountWarn loopY("CMS::run", "waiting for SLT installation", 2);
+ while (_slt == NULL && !_should_terminate) {
+ CGC_lock->wait(true, 200);
+ loopY.tick();
+ }
+ clear_CMS_flag(CMS_cms_wants_token);
+ }
+
+ while (!_should_terminate) {
+ sleepBeforeNextCycle();
+ if (_should_terminate) break;
+ _collector->collect_in_background(false); // !clear_all_soft_refs
+ }
+ assert(_should_terminate, "just checking");
+ // Check that the state of any protocol for synchronization
+ // between background (CMS) and foreground collector is "clean"
+ // (i.e. will not potentially block the foreground collector,
+ // requiring action by us).
+ verify_ok_to_terminate();
+ // Signal that it is terminated
+ {
+ MutexLockerEx mu(Terminator_lock,
+ Mutex::_no_safepoint_check_flag);
+ assert(_cmst == this, "Weird!");
+ _cmst = NULL;
+ Terminator_lock->notify();
+ }
+
+ // Thread destructor usually does this..
+ ThreadLocalStorage::set_thread(NULL);
+}
+
+#ifndef PRODUCT
+void ConcurrentMarkSweepThread::verify_ok_to_terminate() const {
+ assert(!(CGC_lock->owned_by_self() || cms_thread_has_cms_token() ||
+ cms_thread_wants_cms_token()),
+ "Must renounce all worldly possessions and desires for nirvana");
+ _collector->verify_ok_to_terminate();
+}
+#endif
+
+// create and start a new ConcurrentMarkSweep Thread for given CMS generation
+ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::start(CMSCollector* collector) {
+ if (!_should_terminate) {
+ assert(cmst() == NULL, "start() called twice?");
+ ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);
+ assert(cmst() == th, "Where did the just-created CMS thread go?");
+ return th;
+ }
+ return NULL;
+}
+
+void ConcurrentMarkSweepThread::stop() {
+ if (CMSIncrementalMode) {
+ // Disable incremental mode and wake up the thread so it notices the change.
+ disable_icms();
+ start_icms();
+ }
+ // it is ok to take late safepoints here, if needed
+ {
+ MutexLockerEx x(Terminator_lock);
+ _should_terminate = true;
+ }
+ { // Now post a notify on CGC_lock so as to nudge
+ // CMS thread(s) that might be slumbering in
+ // sleepBeforeNextCycle.
+ MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
+ CGC_lock->notify_all();
+ }
+ { // Now wait until (all) CMS thread(s) have exited
+ MutexLockerEx x(Terminator_lock);
+ while(cmst() != NULL) {
+ Terminator_lock->wait();
+ }
+ }
+}
+
+void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {
+ assert(tc != NULL, "Null ThreadClosure");
+ if (_cmst != NULL) {
+ tc->do_thread(_cmst);
+ }
+ assert(Universe::is_fully_initialized(),
+ "Called too early, make sure heap is fully initialized");
+ if (_collector != NULL) {
+ AbstractWorkGang* gang = _collector->conc_workers();
+ if (gang != NULL) {
+ gang->threads_do(tc);
+ }
+ }
+}
+
+void ConcurrentMarkSweepThread::print_on(outputStream* st) const {
+ st->print("\"%s\" ", name());
+ Thread::print_on(st);
+ st->cr();
+}
+
+void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {
+ if (_cmst != NULL) {
+ _cmst->print_on(st);
+ }
+ if (_collector != NULL) {
+ AbstractWorkGang* gang = _collector->conc_workers();
+ if (gang != NULL) {
+ gang->print_worker_threads_on(st);
+ }
+ }
+}
+
+void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {
+ assert(UseConcMarkSweepGC, "just checking");
+
+ MutexLockerEx x(CGC_lock,
+ Mutex::_no_safepoint_check_flag);
+ if (!is_cms_thread) {
+ assert(Thread::current()->is_VM_thread(), "Not a VM thread");
+ CMSSynchronousYieldRequest yr;
+ while (CMS_flag_is_set(CMS_cms_has_token)) {
+ // indicate that we want to get the token
+ set_CMS_flag(CMS_vm_wants_token);
+ CGC_lock->wait(true);
+ }
+ // claim the token and proceed
+ clear_CMS_flag(CMS_vm_wants_token);
+ set_CMS_flag(CMS_vm_has_token);
+ } else {
+ assert(Thread::current()->is_ConcurrentGC_thread(),
+ "Not a CMS thread");
+ // The following barrier assumes there's only one CMS thread.
+ // This will need to be modified is there are more CMS threads than one.
+ while (CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token)) {
+ set_CMS_flag(CMS_cms_wants_token);
+ CGC_lock->wait(true);
+ }
+ // claim the token
+ clear_CMS_flag(CMS_cms_wants_token);
+ set_CMS_flag(CMS_cms_has_token);
+ }
+}
+
+void ConcurrentMarkSweepThread::desynchronize(bool is_cms_thread) {
+ assert(UseConcMarkSweepGC, "just checking");
+
+ MutexLockerEx x(CGC_lock,
+ Mutex::_no_safepoint_check_flag);
+ if (!is_cms_thread) {
+ assert(Thread::current()->is_VM_thread(), "Not a VM thread");
+ assert(CMS_flag_is_set(CMS_vm_has_token), "just checking");
+ clear_CMS_flag(CMS_vm_has_token);
+ if (CMS_flag_is_set(CMS_cms_wants_token)) {
+ // wake-up a waiting CMS thread
+ CGC_lock->notify();
+ }
+ assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),
+ "Should have been cleared");
+ } else {
+ assert(Thread::current()->is_ConcurrentGC_thread(),
+ "Not a CMS thread");
+ assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");
+ clear_CMS_flag(CMS_cms_has_token);
+ if (CMS_flag_is_set(CMS_vm_wants_token)) {
+ // wake-up a waiting VM thread
+ CGC_lock->notify();
+ }
+ assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
+ "Should have been cleared");
+ }
+}
+
+// Wait until the next synchronous GC or a timeout, whichever is earlier.
+void ConcurrentMarkSweepThread::wait_on_cms_lock(long t) {
+ MutexLockerEx x(CGC_lock,
+ Mutex::_no_safepoint_check_flag);
+ set_CMS_flag(CMS_cms_wants_token); // to provoke notifies
+ CGC_lock->wait(Mutex::_no_safepoint_check_flag, t);
+ clear_CMS_flag(CMS_cms_wants_token);
+ assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
+ "Should not be set");
+}
+
+void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {
+ while (!_should_terminate) {
+ if (CMSIncrementalMode) {
+ icms_wait();
+ return;
+ } else {
+ // Wait until the next synchronous GC or a timeout, whichever is earlier
+ wait_on_cms_lock(CMSWaitDuration);
+ }
+ // Check if we should start a CMS collection cycle
+ if (_collector->shouldConcurrentCollect()) {
+ return;
+ }
+ // .. collection criterion not yet met, let's go back
+ // and wait some more
+ }
+}
+
+// Incremental CMS
+void ConcurrentMarkSweepThread::start_icms() {
+ assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
+ MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
+ trace_state("start_icms");
+ _should_run = true;
+ iCMS_lock->notify_all();
+}
+
+void ConcurrentMarkSweepThread::stop_icms() {
+ assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
+ MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
+ if (!_should_stop) {
+ trace_state("stop_icms");
+ _should_stop = true;
+ _should_run = false;
+ asynchronous_yield_request();
+ iCMS_lock->notify_all();
+ }
+}
+
+void ConcurrentMarkSweepThread::icms_wait() {
+ assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
+ if (_should_stop && icms_enabled()) {
+ MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
+ trace_state("pause_icms");
+ _collector->stats().stop_cms_timer();
+ while(!_should_run && icms_enabled()) {
+ iCMS_lock->wait(Mutex::_no_safepoint_check_flag);
+ }
+ _collector->stats().start_cms_timer();
+ _should_stop = false;
+ trace_state("pause_icms end");
+ }
+}
+
+// Note: this method, although exported by the ConcurrentMarkSweepThread,
+// which is a non-JavaThread, can only be called by a JavaThread.
+// Currently this is done at vm creation time (post-vm-init) by the
+// main/Primordial (Java)Thread.
+// XXX Consider changing this in the future to allow the CMS thread
+// itself to create this thread?
+void ConcurrentMarkSweepThread::makeSurrogateLockerThread(TRAPS) {
+ assert(UseConcMarkSweepGC, "SLT thread needed only for CMS GC");
+ assert(_slt == NULL, "SLT already created");
+ _slt = SurrogateLockerThread::make(THREAD);
+}