hotspot/src/share/vm/gc_implementation/shared/concurrentGCThread.cpp - platform/libcore - Git at Google

 /*
  * Copyright (c) 2001, 2009, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */

 // CopyrightVersion 1.2

 # include "incls/_precompiled.incl"
 # include "incls/_concurrentGCThread.cpp.incl"

 int  ConcurrentGCThread::_CGC_flag            = CGC_nil;

 SuspendibleThreadSet ConcurrentGCThread::_sts;

 ConcurrentGCThread::ConcurrentGCThread() :
   _should_terminate(false), _has_terminated(false) {
   _sts.initialize();
 };

 void ConcurrentGCThread::stopWorldAndDo(VoidClosure* op) {
   MutexLockerEx x(Heap_lock,
                   Mutex::_no_safepoint_check_flag);
   // warning("CGC: about to try stopping world");
   SafepointSynchronize::begin();
   // warning("CGC: successfully stopped world");
   op->do_void();
   SafepointSynchronize::end();
   // warning("CGC: successfully restarted world");
 }

 void ConcurrentGCThread::safepoint_synchronize() {
   _sts.suspend_all();
 }

 void ConcurrentGCThread::safepoint_desynchronize() {
   _sts.resume_all();
 }

 void ConcurrentGCThread::create_and_start() {
   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 (!_should_terminate && !DisableStartThread) {
       os::start_thread(this);
     }
   }
 }

 void ConcurrentGCThread::initialize_in_thread() {
   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");
 }

 void ConcurrentGCThread::wait_for_universe_init() {
   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
   while (!is_init_completed() && !_should_terminate) {
     CGC_lock->wait(Mutex::_no_safepoint_check_flag, 200);
   }
 }

 void ConcurrentGCThread::terminate() {
   // Signal that it is terminated
   {
     MutexLockerEx mu(Terminator_lock,
                      Mutex::_no_safepoint_check_flag);
     _has_terminated = true;
     Terminator_lock->notify();
   }

   // Thread destructor usually does this..
   ThreadLocalStorage::set_thread(NULL);
 }


 void SuspendibleThreadSet::initialize_work() {
   MutexLocker x(STS_init_lock);
   if (!_initialized) {
     _m             = new Monitor(Mutex::leaf,
                                  "SuspendibleThreadSetLock", true);
     _async         = 0;
     _async_stop    = false;
     _async_stopped = 0;
     _initialized   = true;
   }
 }

 void SuspendibleThreadSet::join() {
   initialize();
   MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
   while (_async_stop) _m->wait(Mutex::_no_safepoint_check_flag);
   _async++;
   assert(_async > 0, "Huh.");
 }

 void SuspendibleThreadSet::leave() {
   assert(_initialized, "Must be initialized.");
   MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
   _async--;
   assert(_async >= 0, "Huh.");
   if (_async_stop) _m->notify_all();
 }

 void SuspendibleThreadSet::yield(const char* id) {
   assert(_initialized, "Must be initialized.");
   if (_async_stop) {
     MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
     if (_async_stop) {
       _async_stopped++;
       assert(_async_stopped > 0, "Huh.");
       if (_async_stopped == _async) {
         if (ConcGCYieldTimeout > 0) {
           double now = os::elapsedTime();
           guarantee((now - _suspend_all_start) * 1000.0 <
                     (double)ConcGCYieldTimeout,
                     "Long delay; whodunit?");
         }
       }
       _m->notify_all();
       while (_async_stop) _m->wait(Mutex::_no_safepoint_check_flag);
       _async_stopped--;
       assert(_async >= 0, "Huh");
       _m->notify_all();
     }
   }
 }

 void SuspendibleThreadSet::suspend_all() {
   initialize();  // If necessary.
   if (ConcGCYieldTimeout > 0) {
     _suspend_all_start = os::elapsedTime();
   }
   MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
   assert(!_async_stop, "Only one at a time.");
   _async_stop = true;
   while (_async_stopped < _async) _m->wait(Mutex::_no_safepoint_check_flag);
 }

 void SuspendibleThreadSet::resume_all() {
   assert(_initialized, "Must be initialized.");
   MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
   assert(_async_stopped == _async, "Huh.");
   _async_stop = false;
   _m->notify_all();
 }

 static void _sltLoop(JavaThread* thread, TRAPS) {
   SurrogateLockerThread* slt = (SurrogateLockerThread*)thread;
   slt->loop();
 }

 SurrogateLockerThread::SurrogateLockerThread() :
   JavaThread(&_sltLoop),
   _monitor(Mutex::nonleaf, "SLTMonitor"),
   _buffer(empty)
 {}

 SurrogateLockerThread* SurrogateLockerThread::make(TRAPS) {
   klassOop k =
     SystemDictionary::resolve_or_fail(vmSymbolHandles::java_lang_Thread(),
                                       true, CHECK_NULL);
   instanceKlassHandle klass (THREAD, k);
   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK_NULL);

   const char thread_name[] = "Surrogate Locker Thread (Concurrent GC)";
   Handle string = java_lang_String::create_from_str(thread_name, CHECK_NULL);

   // Initialize thread_oop to put it into the system threadGroup
   Handle thread_group (THREAD, Universe::system_thread_group());
   JavaValue result(T_VOID);
   JavaCalls::call_special(&result, thread_oop,
                           klass,
                           vmSymbolHandles::object_initializer_name(),
                           vmSymbolHandles::threadgroup_string_void_signature(),
                           thread_group,
                           string,
                           CHECK_NULL);

   SurrogateLockerThread* res;
   {
     MutexLocker mu(Threads_lock);
     res = new SurrogateLockerThread();

     // At this point it may be possible that no osthread was created for the
     // JavaThread due to lack of memory. We would have to throw an exception
     // in that case. However, since this must work and we do not allow
     // exceptions anyway, check and abort if this fails.
     if (res == NULL || res->osthread() == NULL) {
       vm_exit_during_initialization("java.lang.OutOfMemoryError",
                                     "unable to create new native thread");
     }
     java_lang_Thread::set_thread(thread_oop(), res);
     java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
     java_lang_Thread::set_daemon(thread_oop());

     res->set_threadObj(thread_oop());
     Threads::add(res);
     Thread::start(res);
   }
   os::yield(); // This seems to help with initial start-up of SLT
   return res;
 }

 void SurrogateLockerThread::manipulatePLL(SLT_msg_type msg) {
   MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag);
   assert(_buffer == empty, "Should be empty");
   assert(msg != empty, "empty message");
   _buffer = msg;
   while (_buffer != empty) {
     _monitor.notify();
     _monitor.wait(Mutex::_no_safepoint_check_flag);
   }
 }

 // ======= Surrogate Locker Thread =============

 void SurrogateLockerThread::loop() {
   BasicLock pll_basic_lock;
   SLT_msg_type msg;
   debug_only(unsigned int owned = 0;)

   while (/* !isTerminated() */ 1) {
     {
       MutexLocker x(&_monitor);
       // Since we are a JavaThread, we can't be here at a safepoint.
       assert(!SafepointSynchronize::is_at_safepoint(),
              "SLT is a JavaThread");
       // wait for msg buffer to become non-empty
       while (_buffer == empty) {
         _monitor.notify();
         _monitor.wait();
       }
       msg = _buffer;
     }
     switch(msg) {
       case acquirePLL: {
         instanceRefKlass::acquire_pending_list_lock(&pll_basic_lock);
         debug_only(owned++;)
         break;
       }
       case releaseAndNotifyPLL: {
         assert(owned > 0, "Don't have PLL");
         instanceRefKlass::release_and_notify_pending_list_lock(&pll_basic_lock);
         debug_only(owned--;)
         break;
       }
       case empty:
       default: {
         guarantee(false,"Unexpected message in _buffer");
         break;
       }
     }
     {
       MutexLocker x(&_monitor);
       // Since we are a JavaThread, we can't be here at a safepoint.
       assert(!SafepointSynchronize::is_at_safepoint(),
              "SLT is a JavaThread");
       _buffer = empty;
       _monitor.notify();
     }
   }
   assert(!_monitor.owned_by_self(), "Should unlock before exit.");
 }


 // ===== STS Access From Outside CGCT =====

 void ConcurrentGCThread::stsYield(const char* id) {
   assert( Thread::current()->is_ConcurrentGC_thread(),
           "only a conc GC thread can call this" );
   _sts.yield(id);
 }

 bool ConcurrentGCThread::stsShouldYield() {
   assert( Thread::current()->is_ConcurrentGC_thread(),
           "only a conc GC thread can call this" );
   return _sts.should_yield();
 }

 void ConcurrentGCThread::stsJoin() {
   assert( Thread::current()->is_ConcurrentGC_thread(),
           "only a conc GC thread can call this" );
   _sts.join();
 }

 void ConcurrentGCThread::stsLeave() {
   assert( Thread::current()->is_ConcurrentGC_thread(),
           "only a conc GC thread can call this" );
   _sts.leave();
 }
	/*
	* Copyright (c) 2001, 2009, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*
	*/

	// CopyrightVersion 1.2

	# include "incls/_precompiled.incl"
	# include "incls/_concurrentGCThread.cpp.incl"

	int ConcurrentGCThread::_CGC_flag = CGC_nil;

	SuspendibleThreadSet ConcurrentGCThread::_sts;

	ConcurrentGCThread::ConcurrentGCThread() :
	_should_terminate(false), _has_terminated(false) {
	_sts.initialize();
	};

	void ConcurrentGCThread::stopWorldAndDo(VoidClosure* op) {
	MutexLockerEx x(Heap_lock,
	Mutex::_no_safepoint_check_flag);
	// warning("CGC: about to try stopping world");
	SafepointSynchronize::begin();
	// warning("CGC: successfully stopped world");
	op->do_void();
	SafepointSynchronize::end();
	// warning("CGC: successfully restarted world");
	}

	void ConcurrentGCThread::safepoint_synchronize() {
	_sts.suspend_all();
	}

	void ConcurrentGCThread::safepoint_desynchronize() {
	_sts.resume_all();
	}

	void ConcurrentGCThread::create_and_start() {
	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 (!_should_terminate && !DisableStartThread) {
	os::start_thread(this);
	}
	}
	}

	void ConcurrentGCThread::initialize_in_thread() {
	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");
	}

	void ConcurrentGCThread::wait_for_universe_init() {
	MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
	while (!is_init_completed() && !_should_terminate) {
	CGC_lock->wait(Mutex::_no_safepoint_check_flag, 200);
	}
	}

	void ConcurrentGCThread::terminate() {
	// Signal that it is terminated
	{
	MutexLockerEx mu(Terminator_lock,
	Mutex::_no_safepoint_check_flag);
	_has_terminated = true;
	Terminator_lock->notify();
	}

	// Thread destructor usually does this..
	ThreadLocalStorage::set_thread(NULL);
	}


	void SuspendibleThreadSet::initialize_work() {
	MutexLocker x(STS_init_lock);
	if (!_initialized) {
	_m = new Monitor(Mutex::leaf,
	"SuspendibleThreadSetLock", true);
	_async = 0;
	_async_stop = false;
	_async_stopped = 0;
	_initialized = true;
	}
	}

	void SuspendibleThreadSet::join() {
	initialize();
	MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
	while (_async_stop) _m->wait(Mutex::_no_safepoint_check_flag);
	_async++;
	assert(_async > 0, "Huh.");
	}

	void SuspendibleThreadSet::leave() {
	assert(_initialized, "Must be initialized.");
	MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
	_async--;
	assert(_async >= 0, "Huh.");
	if (_async_stop) _m->notify_all();
	}

	void SuspendibleThreadSet::yield(const char* id) {
	assert(_initialized, "Must be initialized.");
	if (_async_stop) {
	MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
	if (_async_stop) {
	_async_stopped++;
	assert(_async_stopped > 0, "Huh.");
	if (_async_stopped == _async) {
	if (ConcGCYieldTimeout > 0) {
	double now = os::elapsedTime();
	guarantee((now - _suspend_all_start) * 1000.0 <
	(double)ConcGCYieldTimeout,
	"Long delay; whodunit?");
	}
	}
	_m->notify_all();
	while (_async_stop) _m->wait(Mutex::_no_safepoint_check_flag);
	_async_stopped--;
	assert(_async >= 0, "Huh");
	_m->notify_all();
	}
	}
	}

	void SuspendibleThreadSet::suspend_all() {
	initialize(); // If necessary.
	if (ConcGCYieldTimeout > 0) {
	_suspend_all_start = os::elapsedTime();
	}
	MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
	assert(!_async_stop, "Only one at a time.");
	_async_stop = true;
	while (_async_stopped < _async) _m->wait(Mutex::_no_safepoint_check_flag);
	}

	void SuspendibleThreadSet::resume_all() {
	assert(_initialized, "Must be initialized.");
	MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
	assert(_async_stopped == _async, "Huh.");
	_async_stop = false;
	_m->notify_all();
	}

	static void _sltLoop(JavaThread* thread, TRAPS) {
	SurrogateLockerThread* slt = (SurrogateLockerThread*)thread;
	slt->loop();
	}

	SurrogateLockerThread::SurrogateLockerThread() :
	JavaThread(&_sltLoop),
	_monitor(Mutex::nonleaf, "SLTMonitor"),
	_buffer(empty)
	{}

	SurrogateLockerThread* SurrogateLockerThread::make(TRAPS) {
	klassOop k =
	SystemDictionary::resolve_or_fail(vmSymbolHandles::java_lang_Thread(),
	true, CHECK_NULL);
	instanceKlassHandle klass (THREAD, k);
	instanceHandle thread_oop = klass->allocate_instance_handle(CHECK_NULL);

	const char thread_name[] = "Surrogate Locker Thread (Concurrent GC)";
	Handle string = java_lang_String::create_from_str(thread_name, CHECK_NULL);

	// Initialize thread_oop to put it into the system threadGroup
	Handle thread_group (THREAD, Universe::system_thread_group());
	JavaValue result(T_VOID);
	JavaCalls::call_special(&result, thread_oop,
	klass,
	vmSymbolHandles::object_initializer_name(),
	vmSymbolHandles::threadgroup_string_void_signature(),
	thread_group,
	string,
	CHECK_NULL);

	SurrogateLockerThread* res;
	{
	MutexLocker mu(Threads_lock);
	res = new SurrogateLockerThread();

	// At this point it may be possible that no osthread was created for the
	// JavaThread due to lack of memory. We would have to throw an exception
	// in that case. However, since this must work and we do not allow
	// exceptions anyway, check and abort if this fails.
	if (res == NULL \|\| res->osthread() == NULL) {
	vm_exit_during_initialization("java.lang.OutOfMemoryError",
	"unable to create new native thread");
	}
	java_lang_Thread::set_thread(thread_oop(), res);
	java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
	java_lang_Thread::set_daemon(thread_oop());

	res->set_threadObj(thread_oop());
	Threads::add(res);
	Thread::start(res);
	}
	os::yield(); // This seems to help with initial start-up of SLT
	return res;
	}

	void SurrogateLockerThread::manipulatePLL(SLT_msg_type msg) {
	MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag);
	assert(_buffer == empty, "Should be empty");
	assert(msg != empty, "empty message");
	_buffer = msg;
	while (_buffer != empty) {
	_monitor.notify();
	_monitor.wait(Mutex::_no_safepoint_check_flag);
	}
	}

	// ======= Surrogate Locker Thread =============

	void SurrogateLockerThread::loop() {
	BasicLock pll_basic_lock;
	SLT_msg_type msg;
	debug_only(unsigned int owned = 0;)

	while (/* !isTerminated() */ 1) {
	{
	MutexLocker x(&_monitor);
	// Since we are a JavaThread, we can't be here at a safepoint.
	assert(!SafepointSynchronize::is_at_safepoint(),
	"SLT is a JavaThread");
	// wait for msg buffer to become non-empty
	while (_buffer == empty) {
	_monitor.notify();
	_monitor.wait();
	}
	msg = _buffer;
	}
	switch(msg) {
	case acquirePLL: {
	instanceRefKlass::acquire_pending_list_lock(&pll_basic_lock);
	debug_only(owned++;)
	break;
	}
	case releaseAndNotifyPLL: {
	assert(owned > 0, "Don't have PLL");
	instanceRefKlass::release_and_notify_pending_list_lock(&pll_basic_lock);
	debug_only(owned--;)
	break;
	}
	case empty:
	default: {
	guarantee(false,"Unexpected message in _buffer");
	break;
	}
	}
	{
	MutexLocker x(&_monitor);
	// Since we are a JavaThread, we can't be here at a safepoint.
	assert(!SafepointSynchronize::is_at_safepoint(),
	"SLT is a JavaThread");
	_buffer = empty;
	_monitor.notify();
	}
	}
	assert(!_monitor.owned_by_self(), "Should unlock before exit.");
	}


	// ===== STS Access From Outside CGCT =====

	void ConcurrentGCThread::stsYield(const char* id) {
	assert( Thread::current()->is_ConcurrentGC_thread(),
	"only a conc GC thread can call this" );
	_sts.yield(id);
	}

	bool ConcurrentGCThread::stsShouldYield() {
	assert( Thread::current()->is_ConcurrentGC_thread(),
	"only a conc GC thread can call this" );
	return _sts.should_yield();
	}

	void ConcurrentGCThread::stsJoin() {
	assert( Thread::current()->is_ConcurrentGC_thread(),
	"only a conc GC thread can call this" );
	_sts.join();
	}

	void ConcurrentGCThread::stsLeave() {
	assert( Thread::current()->is_ConcurrentGC_thread(),
	"only a conc GC thread can call this" );
	_sts.leave();
	}