heap/GCThread.cpp

   1 /*
   2  * Copyright (C) 2012 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 #include <wtf/PassOwnPtr.h>
  36
  37 namespace JSC {
  38
  39 GCThread::GCThread(GCThreadSharedData& shared, SlotVisitor* slotVisitor, CopyVisitor* copyVisitor)
  40     : m_threadID(0)
  41     , m_shared(shared)
  42     , m_slotVisitor(WTF::adoptPtr(slotVisitor))
  43     , m_copyVisitor(WTF::adoptPtr(copyVisitor))
  44 {
  45 }
  46
  47 ThreadIdentifier GCThread::threadID()
  48 {
  49     ASSERT(m_threadID);
  50     return m_threadID;
  51 }
  52
  53 void GCThread::initializeThreadID(ThreadIdentifier threadID)
  54 {
  55     ASSERT(!m_threadID);
  56     m_threadID = threadID;
  57 }
  58
  59 SlotVisitor* GCThread::slotVisitor()
  60 {
  61     ASSERT(m_slotVisitor);
  62     return m_slotVisitor.get();
  63 }
  64
  65 CopyVisitor* GCThread::copyVisitor()
  66 {
  67     ASSERT(m_copyVisitor);
  68     return m_copyVisitor.get();
  69 }
  70
  71 GCPhase GCThread::waitForNextPhase()
  72 {
  73     std::unique_lock<std::mutex> lock(m_shared.m_phaseMutex);
  74     m_shared.m_phaseConditionVariable.wait(lock, [this] { return !m_shared.m_gcThreadsShouldWait; });
  75
  76     m_shared.m_numberOfActiveGCThreads--;
  77     if (!m_shared.m_numberOfActiveGCThreads)
  78         m_shared.m_activityConditionVariable.notify_one();
  79
  80     m_shared.m_phaseConditionVariable.wait(lock, [this] { return m_shared.m_currentPhase != NoPhase; });
  81     m_shared.m_numberOfActiveGCThreads++;
  82     return m_shared.m_currentPhase;
  83 }
  84
  85 void GCThread::gcThreadMain()
  86 {
  87     GCPhase currentPhase;
  88 #if ENABLE(PARALLEL_GC)
  89     WTF::registerGCThread();
  90 #endif
  91     // Wait for the main thread to finish creating and initializing us. The main thread grabs this lock before
  92     // creating this thread. We aren't guaranteed to have a valid threadID until the main thread releases this lock.
  93     {
  94         std::lock_guard<std::mutex> lock(m_shared.m_phaseMutex);
  95     }
  96     {
  97         ParallelModeEnabler enabler(*m_slotVisitor);
  98         while ((currentPhase = waitForNextPhase()) != Exit) {
  99             // Note: Each phase is responsible for its own termination conditions. The comments below describe
 100             // how each phase reaches termination.
 101             switch (currentPhase) {
 102             case Mark:
 103                 m_slotVisitor->drainFromShared(SlotVisitor::SlaveDrain);
 104                 // GCThreads only return from drainFromShared() if the main thread sets the m_parallelMarkersShouldExit
 105                 // flag in the GCThreadSharedData. The only way the main thread sets that flag is if it realizes
 106                 // that all of the various subphases in Heap::markRoots() have been fully finished and there is
 107                 // no more marking work to do and all of the GCThreads are idle, meaning no more work can be generated.
 108                 break;
 109             case Copy:
 110                 // We don't have to call startCopying() because it's called for us on the main thread to avoid a
 111                 // race condition.
 112                 m_copyVisitor->copyFromShared();
 113                 // We know we're done copying when we return from copyFromShared() because we would
 114                 // only do so if there were no more chunks of copying work left to do. When there is no
 115                 // more copying work to do, the main thread will wait in CopiedSpace::doneCopying() until
 116                 // all of the blocks that the GCThreads borrowed have been returned. doneCopying()
 117                 // returns our borrowed CopiedBlock, allowing the copying phase to finish.
 118                 m_copyVisitor->doneCopying();
 119                 break;
 120             case NoPhase:
 121                 RELEASE_ASSERT_NOT_REACHED();
 122                 break;
 123             case Exit:
 124                 RELEASE_ASSERT_NOT_REACHED();
 125                 break;
 126             }
 127         }
 128     }
 129 }
 130
 131 void GCThread::gcThreadStartFunc(void* data)
 132 {
 133     GCThread* thread = static_cast<GCThread*>(data);
 134     thread->gcThreadMain();
 135 }
 136
 137 } // namespace JSC