Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2001, 2006, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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  */

 # 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);

 }