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
37namespace JSC {
38
39GCThread::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
47ThreadIdentifier GCThread::threadID()
48{
49    ASSERT(m_threadID);
50    return m_threadID;
51}
52
53void GCThread::initializeThreadID(ThreadIdentifier threadID)
54{
55    ASSERT(!m_threadID);
56    m_threadID = threadID;
57}
58
59SlotVisitor* GCThread::slotVisitor()
60{
61    ASSERT(m_slotVisitor);
62    return m_slotVisitor.get();
63}
64
65CopyVisitor* GCThread::copyVisitor()
66{
67    ASSERT(m_copyVisitor);
68    return m_copyVisitor.get();
69}
70
71GCPhase 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
85void 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
131void GCThread::gcThreadStartFunc(void* data)
132{
133    GCThread* thread = static_cast<GCThread*>(data);
134    thread->gcThreadMain();
135}
136
137} // namespace JSC
138