hotspot/src/share/vm/gc/g1/satbMarkQueue.cpp - platform/libcore - Git at Google

 /*
  * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */

 #include "precompiled.hpp"
 #include "gc/g1/g1CollectedHeap.inline.hpp"
 #include "gc/g1/satbMarkQueue.hpp"
 #include "gc/shared/collectedHeap.hpp"
 #include "memory/allocation.inline.hpp"
 #include "oops/oop.inline.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "runtime/safepoint.hpp"
 #include "runtime/thread.hpp"
 #include "runtime/vmThread.hpp"

 SATBMarkQueue::SATBMarkQueue(SATBMarkQueueSet* qset, bool permanent) :
   // SATB queues are only active during marking cycles. We create
   // them with their active field set to false. If a thread is
   // created during a cycle and its SATB queue needs to be activated
   // before the thread starts running, we'll need to set its active
   // field to true. This is done in JavaThread::initialize_queues().
   PtrQueue(qset, permanent, false /* active */)
 { }

 void SATBMarkQueue::flush() {
   // Filter now to possibly save work later.  If filtering empties the
   // buffer then flush_impl can deallocate the buffer.
   filter();
   flush_impl();
 }

 // Return true if a SATB buffer entry refers to an object that
 // requires marking.
 //
 // The entry must point into the G1 heap.  In particular, it must not
 // be a NULL pointer.  NULL pointers are pre-filtered and never
 // inserted into a SATB buffer.
 //
 // An entry that is below the NTAMS pointer for the containing heap
 // region requires marking. Such an entry must point to a valid object.
 //
 // An entry that is at least the NTAMS pointer for the containing heap
 // region might be any of the following, none of which should be marked.
 //
 // * A reference to an object allocated since marking started.
 //   According to SATB, such objects are implicitly kept live and do
 //   not need to be dealt with via SATB buffer processing.
 //
 // * A reference to a young generation object. Young objects are
 //   handled separately and are not marked by concurrent marking.
 //
 // * A stale reference to a young generation object. If a young
 //   generation object reference is recorded and not filtered out
 //   before being moved by a young collection, the reference becomes
 //   stale.
 //
 // * A stale reference to an eagerly reclaimed humongous object.  If a
 //   humongous object is recorded and then reclaimed, the reference
 //   becomes stale.
 //
 // The stale reference cases are implicitly handled by the NTAMS
 // comparison. Because of the possibility of stale references, buffer
 // processing must be somewhat circumspect and not assume entries
 // in an unfiltered buffer refer to valid objects.

 inline bool requires_marking(const void* entry, G1CollectedHeap* heap) {
   // Includes rejection of NULL pointers.
   assert(heap->is_in_reserved(entry),
          "Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry));

   HeapRegion* region = heap->heap_region_containing(entry);
   assert(region != NULL, "No region for " PTR_FORMAT, p2i(entry));
   if (entry >= region->next_top_at_mark_start()) {
     return false;
   }

   assert(((oop)entry)->is_oop(true /* ignore mark word */),
          "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry));

   return true;
 }

 inline bool retain_entry(const void* entry, G1CollectedHeap* heap) {
   return requires_marking(entry, heap) && !heap->isMarkedNext((oop)entry);
 }

 // This method removes entries from a SATB buffer that will not be
 // useful to the concurrent marking threads.  Entries are retained if
 // they require marking and are not already marked. Retained entries
 // are compacted toward the top of the buffer.

 void SATBMarkQueue::filter() {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   void** buf = _buf;

   if (buf == NULL) {
     // nothing to do
     return;
   }

   // Two-fingered compaction toward the end.
   void** src = &buf[index()];
   void** dst = &buf[capacity()];
   assert(src <= dst, "invariant");
   for ( ; src < dst; ++src) {
     // Search low to high for an entry to keep.
     void* entry = *src;
     if (retain_entry(entry, g1h)) {
       // Found keeper.  Search high to low for an entry to discard.
       while (src < --dst) {
         if (!retain_entry(*dst, g1h)) {
           *dst = entry;         // Replace discard with keeper.
           break;
         }
       }
       // If discard search failed (src == dst), the outer loop will also end.
     }
   }
   // dst points to the lowest retained entry, or the end of the buffer
   // if all the entries were filtered out.
   set_index(dst - buf);
 }

 // This method will first apply the above filtering to the buffer. If
 // post-filtering a large enough chunk of the buffer has been cleared
 // we can re-use the buffer (instead of enqueueing it) and we can just
 // allow the mutator to carry on executing using the same buffer
 // instead of replacing it.

 bool SATBMarkQueue::should_enqueue_buffer() {
   assert(_lock == NULL || _lock->owned_by_self(),
          "we should have taken the lock before calling this");

   // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering.

   // This method should only be called if there is a non-NULL buffer
   // that is full.
   assert(index() == 0, "pre-condition");
   assert(_buf != NULL, "pre-condition");

   filter();

   size_t cap = capacity();
   size_t percent_used = ((cap - index()) * 100) / cap;
   bool should_enqueue = percent_used > G1SATBBufferEnqueueingThresholdPercent;
   return should_enqueue;
 }

 void SATBMarkQueue::apply_closure_and_empty(SATBBufferClosure* cl) {
   assert(SafepointSynchronize::is_at_safepoint(),
          "SATB queues must only be processed at safepoints");
   if (_buf != NULL) {
     cl->do_buffer(&_buf[index()], size());
     reset();
   }
 }

 #ifndef PRODUCT
 // Helpful for debugging

 static void print_satb_buffer(const char* name,
                               void** buf,
                               size_t index,
                               size_t capacity) {
   tty->print_cr("  SATB BUFFER [%s] buf: " PTR_FORMAT " index: " SIZE_FORMAT
                 " capacity: " SIZE_FORMAT,
                 name, p2i(buf), index, capacity);
 }

 void SATBMarkQueue::print(const char* name) {
   print_satb_buffer(name, _buf, index(), capacity());
 }

 #endif // PRODUCT

 SATBMarkQueueSet::SATBMarkQueueSet() :
   PtrQueueSet(),
   _shared_satb_queue(this, true /* permanent */) { }

 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
                                   int process_completed_threshold,
                                   Mutex* lock) {
   PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
   _shared_satb_queue.set_lock(lock);
 }

 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
   t->satb_mark_queue().handle_zero_index();
 }

 #ifdef ASSERT
 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
   log_error(gc, verify)("Expected SATB active state: %s", expected_active ? "ACTIVE" : "INACTIVE");
   log_error(gc, verify)("Actual SATB active states:");
   log_error(gc, verify)("  Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
   for (JavaThread* t = Threads::first(); t; t = t->next()) {
     log_error(gc, verify)("  Thread \"%s\" queue: %s", t->name(), t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
   }
   log_error(gc, verify)("  Shared queue: %s", shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
 }

 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
   // Verify queue set state
   if (is_active() != expected_active) {
     dump_active_states(expected_active);
     guarantee(false, "SATB queue set has an unexpected active state");
   }

   // Verify thread queue states
   for (JavaThread* t = Threads::first(); t; t = t->next()) {
     if (t->satb_mark_queue().is_active() != expected_active) {
       dump_active_states(expected_active);
       guarantee(false, "Thread SATB queue has an unexpected active state");
     }
   }

   // Verify shared queue state
   if (shared_satb_queue()->is_active() != expected_active) {
     dump_active_states(expected_active);
     guarantee(false, "Shared SATB queue has an unexpected active state");
   }
 }
 #endif // ASSERT

 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 #ifdef ASSERT
   verify_active_states(expected_active);
 #endif // ASSERT
   _all_active = active;
   for (JavaThread* t = Threads::first(); t; t = t->next()) {
     t->satb_mark_queue().set_active(active);
   }
   shared_satb_queue()->set_active(active);
 }

 void SATBMarkQueueSet::filter_thread_buffers() {
   for(JavaThread* t = Threads::first(); t; t = t->next()) {
     t->satb_mark_queue().filter();
   }
   shared_satb_queue()->filter();
 }

 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {
   BufferNode* nd = NULL;
   {
     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
     if (_completed_buffers_head != NULL) {
       nd = _completed_buffers_head;
       _completed_buffers_head = nd->next();
       if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
       _n_completed_buffers--;
       if (_n_completed_buffers == 0) _process_completed = false;
     }
   }
   if (nd != NULL) {
     void **buf = BufferNode::make_buffer_from_node(nd);
     size_t index = nd->index();
     size_t size = buffer_size();
     assert(index <= size, "invariant");
     cl->do_buffer(buf + index, size - index);
     deallocate_buffer(nd);
     return true;
   } else {
     return false;
   }
 }

 #ifndef PRODUCT
 // Helpful for debugging

 #define SATB_PRINTER_BUFFER_SIZE 256

 void SATBMarkQueueSet::print_all(const char* msg) {
   char buffer[SATB_PRINTER_BUFFER_SIZE];
   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

   tty->cr();
   tty->print_cr("SATB BUFFERS [%s]", msg);

   BufferNode* nd = _completed_buffers_head;
   int i = 0;
   while (nd != NULL) {
     void** buf = BufferNode::make_buffer_from_node(nd);
     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
     print_satb_buffer(buffer, buf, nd->index(), buffer_size());
     nd = nd->next();
     i += 1;
   }

   for (JavaThread* t = Threads::first(); t; t = t->next()) {
     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
     t->satb_mark_queue().print(buffer);
   }

   shared_satb_queue()->print("Shared");

   tty->cr();
 }
 #endif // PRODUCT

 void SATBMarkQueueSet::abandon_partial_marking() {
   BufferNode* buffers_to_delete = NULL;
   {
     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
     while (_completed_buffers_head != NULL) {
       BufferNode* nd = _completed_buffers_head;
       _completed_buffers_head = nd->next();
       nd->set_next(buffers_to_delete);
       buffers_to_delete = nd;
     }
     _completed_buffers_tail = NULL;
     _n_completed_buffers = 0;
     DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
   }
   while (buffers_to_delete != NULL) {
     BufferNode* nd = buffers_to_delete;
     buffers_to_delete = nd->next();
     deallocate_buffer(nd);
   }
   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
   // So we can safely manipulate these queues.
   for (JavaThread* t = Threads::first(); t; t = t->next()) {
     t->satb_mark_queue().reset();
   }
  shared_satb_queue()->reset();
 }
	/*
	* Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*
	*/

	#include "precompiled.hpp"
	#include "gc/g1/g1CollectedHeap.inline.hpp"
	#include "gc/g1/satbMarkQueue.hpp"
	#include "gc/shared/collectedHeap.hpp"
	#include "memory/allocation.inline.hpp"
	#include "oops/oop.inline.hpp"
	#include "runtime/mutexLocker.hpp"
	#include "runtime/safepoint.hpp"
	#include "runtime/thread.hpp"
	#include "runtime/vmThread.hpp"

	SATBMarkQueue::SATBMarkQueue(SATBMarkQueueSet* qset, bool permanent) :
	// SATB queues are only active during marking cycles. We create
	// them with their active field set to false. If a thread is
	// created during a cycle and its SATB queue needs to be activated
	// before the thread starts running, we'll need to set its active
	// field to true. This is done in JavaThread::initialize_queues().
	PtrQueue(qset, permanent, false /* active */)
	{ }

	void SATBMarkQueue::flush() {
	// Filter now to possibly save work later. If filtering empties the
	// buffer then flush_impl can deallocate the buffer.
	filter();
	flush_impl();
	}

	// Return true if a SATB buffer entry refers to an object that
	// requires marking.
	//
	// The entry must point into the G1 heap. In particular, it must not
	// be a NULL pointer. NULL pointers are pre-filtered and never
	// inserted into a SATB buffer.
	//
	// An entry that is below the NTAMS pointer for the containing heap
	// region requires marking. Such an entry must point to a valid object.
	//
	// An entry that is at least the NTAMS pointer for the containing heap
	// region might be any of the following, none of which should be marked.
	//
	// * A reference to an object allocated since marking started.
	// According to SATB, such objects are implicitly kept live and do
	// not need to be dealt with via SATB buffer processing.
	//
	// * A reference to a young generation object. Young objects are
	// handled separately and are not marked by concurrent marking.
	//
	// * A stale reference to a young generation object. If a young
	// generation object reference is recorded and not filtered out
	// before being moved by a young collection, the reference becomes
	// stale.
	//
	// * A stale reference to an eagerly reclaimed humongous object. If a
	// humongous object is recorded and then reclaimed, the reference
	// becomes stale.
	//
	// The stale reference cases are implicitly handled by the NTAMS
	// comparison. Because of the possibility of stale references, buffer
	// processing must be somewhat circumspect and not assume entries
	// in an unfiltered buffer refer to valid objects.

	inline bool requires_marking(const void* entry, G1CollectedHeap* heap) {
	// Includes rejection of NULL pointers.
	assert(heap->is_in_reserved(entry),
	"Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry));

	HeapRegion* region = heap->heap_region_containing(entry);
	assert(region != NULL, "No region for " PTR_FORMAT, p2i(entry));
	if (entry >= region->next_top_at_mark_start()) {
	return false;
	}

	assert(((oop)entry)->is_oop(true /* ignore mark word */),
	"Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry));

	return true;
	}

	inline bool retain_entry(const void* entry, G1CollectedHeap* heap) {
	return requires_marking(entry, heap) && !heap->isMarkedNext((oop)entry);
	}

	// This method removes entries from a SATB buffer that will not be
	// useful to the concurrent marking threads. Entries are retained if
	// they require marking and are not already marked. Retained entries
	// are compacted toward the top of the buffer.

	void SATBMarkQueue::filter() {
	G1CollectedHeap* g1h = G1CollectedHeap::heap();
	void** buf = _buf;

	if (buf == NULL) {
	// nothing to do
	return;
	}

	// Two-fingered compaction toward the end.
	void** src = &buf[index()];
	void** dst = &buf[capacity()];
	assert(src <= dst, "invariant");
	for ( ; src < dst; ++src) {
	// Search low to high for an entry to keep.
	void* entry = *src;
	if (retain_entry(entry, g1h)) {
	// Found keeper. Search high to low for an entry to discard.
	while (src < --dst) {
	if (!retain_entry(*dst, g1h)) {
	*dst = entry; // Replace discard with keeper.
	break;
	}
	}
	// If discard search failed (src == dst), the outer loop will also end.
	}
	}
	// dst points to the lowest retained entry, or the end of the buffer
	// if all the entries were filtered out.
	set_index(dst - buf);
	}

	// This method will first apply the above filtering to the buffer. If
	// post-filtering a large enough chunk of the buffer has been cleared
	// we can re-use the buffer (instead of enqueueing it) and we can just
	// allow the mutator to carry on executing using the same buffer
	// instead of replacing it.

	bool SATBMarkQueue::should_enqueue_buffer() {
	assert(_lock == NULL \|\| _lock->owned_by_self(),
	"we should have taken the lock before calling this");

	// If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering.

	// This method should only be called if there is a non-NULL buffer
	// that is full.
	assert(index() == 0, "pre-condition");
	assert(_buf != NULL, "pre-condition");

	filter();

	size_t cap = capacity();
	size_t percent_used = ((cap - index()) * 100) / cap;
	bool should_enqueue = percent_used > G1SATBBufferEnqueueingThresholdPercent;
	return should_enqueue;
	}

	void SATBMarkQueue::apply_closure_and_empty(SATBBufferClosure* cl) {
	assert(SafepointSynchronize::is_at_safepoint(),
	"SATB queues must only be processed at safepoints");
	if (_buf != NULL) {
	cl->do_buffer(&_buf[index()], size());
	reset();
	}
	}

	#ifndef PRODUCT
	// Helpful for debugging

	static void print_satb_buffer(const char* name,
	void** buf,
	size_t index,
	size_t capacity) {
	tty->print_cr(" SATB BUFFER [%s] buf: " PTR_FORMAT " index: " SIZE_FORMAT
	" capacity: " SIZE_FORMAT,
	name, p2i(buf), index, capacity);
	}

	void SATBMarkQueue::print(const char* name) {
	print_satb_buffer(name, _buf, index(), capacity());
	}

	#endif // PRODUCT

	SATBMarkQueueSet::SATBMarkQueueSet() :
	PtrQueueSet(),
	_shared_satb_queue(this, true /* permanent */) { }

	void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
	int process_completed_threshold,
	Mutex* lock) {
	PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
	_shared_satb_queue.set_lock(lock);
	}

	void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
	t->satb_mark_queue().handle_zero_index();
	}

	#ifdef ASSERT
	void SATBMarkQueueSet::dump_active_states(bool expected_active) {
	log_error(gc, verify)("Expected SATB active state: %s", expected_active ? "ACTIVE" : "INACTIVE");
	log_error(gc, verify)("Actual SATB active states:");
	log_error(gc, verify)(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
	for (JavaThread* t = Threads::first(); t; t = t->next()) {
	log_error(gc, verify)(" Thread \"%s\" queue: %s", t->name(), t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
	}
	log_error(gc, verify)(" Shared queue: %s", shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
	}

	void SATBMarkQueueSet::verify_active_states(bool expected_active) {
	// Verify queue set state
	if (is_active() != expected_active) {
	dump_active_states(expected_active);
	guarantee(false, "SATB queue set has an unexpected active state");
	}

	// Verify thread queue states
	for (JavaThread* t = Threads::first(); t; t = t->next()) {
	if (t->satb_mark_queue().is_active() != expected_active) {
	dump_active_states(expected_active);
	guarantee(false, "Thread SATB queue has an unexpected active state");
	}
	}

	// Verify shared queue state
	if (shared_satb_queue()->is_active() != expected_active) {
	dump_active_states(expected_active);
	guarantee(false, "Shared SATB queue has an unexpected active state");
	}
	}
	#endif // ASSERT

	void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
	assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
	#ifdef ASSERT
	verify_active_states(expected_active);
	#endif // ASSERT
	_all_active = active;
	for (JavaThread* t = Threads::first(); t; t = t->next()) {
	t->satb_mark_queue().set_active(active);
	}
	shared_satb_queue()->set_active(active);
	}

	void SATBMarkQueueSet::filter_thread_buffers() {
	for(JavaThread* t = Threads::first(); t; t = t->next()) {
	t->satb_mark_queue().filter();
	}
	shared_satb_queue()->filter();
	}

	bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {
	BufferNode* nd = NULL;
	{
	MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
	if (_completed_buffers_head != NULL) {
	nd = _completed_buffers_head;
	_completed_buffers_head = nd->next();
	if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
	_n_completed_buffers--;
	if (_n_completed_buffers == 0) _process_completed = false;
	}
	}
	if (nd != NULL) {
	void **buf = BufferNode::make_buffer_from_node(nd);
	size_t index = nd->index();
	size_t size = buffer_size();
	assert(index <= size, "invariant");
	cl->do_buffer(buf + index, size - index);
	deallocate_buffer(nd);
	return true;
	} else {
	return false;
	}
	}

	#ifndef PRODUCT
	// Helpful for debugging

	#define SATB_PRINTER_BUFFER_SIZE 256

	void SATBMarkQueueSet::print_all(const char* msg) {
	char buffer[SATB_PRINTER_BUFFER_SIZE];
	assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

	tty->cr();
	tty->print_cr("SATB BUFFERS [%s]", msg);

	BufferNode* nd = _completed_buffers_head;
	int i = 0;
	while (nd != NULL) {
	void** buf = BufferNode::make_buffer_from_node(nd);
	jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
	print_satb_buffer(buffer, buf, nd->index(), buffer_size());
	nd = nd->next();
	i += 1;
	}

	for (JavaThread* t = Threads::first(); t; t = t->next()) {
	jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
	t->satb_mark_queue().print(buffer);
	}

	shared_satb_queue()->print("Shared");

	tty->cr();
	}
	#endif // PRODUCT

	void SATBMarkQueueSet::abandon_partial_marking() {
	BufferNode* buffers_to_delete = NULL;
	{
	MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
	while (_completed_buffers_head != NULL) {
	BufferNode* nd = _completed_buffers_head;
	_completed_buffers_head = nd->next();
	nd->set_next(buffers_to_delete);
	buffers_to_delete = nd;
	}
	_completed_buffers_tail = NULL;
	_n_completed_buffers = 0;
	DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
	}
	while (buffers_to_delete != NULL) {
	BufferNode* nd = buffers_to_delete;
	buffers_to_delete = nd->next();
	deallocate_buffer(nd);
	}
	assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
	// So we can safely manipulate these queues.
	for (JavaThread* t = Threads::first(); t; t = t->next()) {
	t->satb_mark_queue().reset();
	}
	shared_satb_queue()->reset();
	}