heap/GCThread.cpp

   1 /*
   2  * Copyright (C) 2012, 2015 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  23  * THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "GCThread.h"
  28
  29 #include "CopyVisitor.h"
  30 #include "CopyVisitorInlines.h"
  31 #include "GCThreadSharedData.h"
  32 #include "JSCInlines.h"
  33 #include "SlotVisitor.h"
  34 #include <wtf/MainThread.h>
  35
  36 namespace JSC {
  37
  38 GCThread::GCThread(GCThreadSharedData& shared, std::unique_ptr<SlotVisitor> slotVisitor, std::unique_ptr<CopyVisitor> copyVisitor)
  39     : m_threadID(0)
  40     , m_shared(shared)
  41     , m_slotVisitor(WTF::move(slotVisitor))
  42     , m_copyVisitor(WTF::move(copyVisitor))
  43 {
  44 }
  45
  46 ThreadIdentifier GCThread::threadID()
  47 {
  48     ASSERT(m_threadID);
  49     return m_threadID;
  50 }
  51
  52 void GCThread::initializeThreadID(ThreadIdentifier threadID)
  53 {
  54     ASSERT(!m_threadID);
  55     m_threadID = threadID;
  56 }
  57
  58 SlotVisitor* GCThread::slotVisitor()
  59 {
  60     ASSERT(m_slotVisitor);
  61     return m_slotVisitor.get();
  62 }
  63
  64 CopyVisitor* GCThread::copyVisitor()
  65 {
  66     ASSERT(m_copyVisitor);
  67     return m_copyVisitor.get();
  68 }
  69
  70 GCPhase GCThread::waitForNextPhase()
  71 {
  72     std::unique_lock<std::mutex> lock(m_shared.m_phaseMutex);
  73     m_shared.m_phaseConditionVariable.wait(lock, [this] { return !m_shared.m_gcThreadsShouldWait; });
  74
  75     m_shared.m_numberOfActiveGCThreads--;
  76     if (!m_shared.m_numberOfActiveGCThreads)
  77         m_shared.m_activityConditionVariable.notify_one();
  78
  79     m_shared.m_phaseConditionVariable.wait(lock, [this] { return m_shared.m_currentPhase != NoPhase; });
  80     m_shared.m_numberOfActiveGCThreads++;
  81     return m_shared.m_currentPhase;
  82 }
  83
  84 void GCThread::gcThreadMain()
  85 {
  86     GCPhase currentPhase;
  87 #if ENABLE(PARALLEL_GC)
  88     WTF::registerGCThread();
  89 #endif
  90     // Wait for the main thread to finish creating and initializing us. The main thread grabs this lock before
  91     // creating this thread. We aren't guaranteed to have a valid threadID until the main thread releases this lock.
  92     {
  93         std::lock_guard<std::mutex> lock(m_shared.m_phaseMutex);
  94     }
  95     {
  96         ParallelModeEnabler enabler(*m_slotVisitor);
  97         while ((currentPhase = waitForNextPhase()) != Exit) {
  98             // Note: Each phase is responsible for its own termination conditions. The comments below describe
  99             // how each phase reaches termination.
 100             switch (currentPhase) {
 101             case Mark:
 102                 m_slotVisitor->drainFromShared(SlotVisitor::SlaveDrain);
 103                 // GCThreads only return from drainFromShared() if the main thread sets the m_parallelMarkersShouldExit
 104                 // flag in the GCThreadSharedData. The only way the main thread sets that flag is if it realizes
 105                 // that all of the various subphases in Heap::markRoots() have been fully finished and there is
 106                 // no more marking work to do and all of the GCThreads are idle, meaning no more work can be generated.
 107                 break;
 108             case Copy:
 109                 // We don't have to call startCopying() because it's called for us on the main thread to avoid a
 110                 // race condition.
 111                 m_copyVisitor->copyFromShared();
 112                 // We know we're done copying when we return from copyFromShared() because we would
 113                 // only do so if there were no more chunks of copying work left to do. When there is no
 114                 // more copying work to do, the main thread will wait in CopiedSpace::doneCopying() until
 115                 // all of the blocks that the GCThreads borrowed have been returned. doneCopying()
 116                 // returns our borrowed CopiedBlock, allowing the copying phase to finish.
 117                 m_copyVisitor->doneCopying();
 118
 119                 WTF::releaseFastMallocFreeMemoryForThisThread();
 120
 121                 break;
 122             case NoPhase:
 123                 RELEASE_ASSERT_NOT_REACHED();
 124                 break;
 125             case Exit:
 126                 RELEASE_ASSERT_NOT_REACHED();
 127                 break;
 128             }
 129         }
 130     }
 131 }
 132
 133 void GCThread::gcThreadStartFunc(void* data)
 134 {
 135     GCThread* thread = static_cast<GCThread*>(data);
 136     thread->gcThreadMain();
 137 }
 138
 139 } // namespace JSC