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 "SlotVisitor.h"
33#include <wtf/MainThread.h>
34#include <wtf/PassOwnPtr.h>
35
36namespace JSC {
37
38GCThread::GCThread(GCThreadSharedData& shared, SlotVisitor* slotVisitor, CopyVisitor* copyVisitor)
39    : m_threadID(0)
40    , m_shared(shared)
41    , m_slotVisitor(WTF::adoptPtr(slotVisitor))
42    , m_copyVisitor(WTF::adoptPtr(copyVisitor))
43{
44}
45
46ThreadIdentifier GCThread::threadID()
47{
48    ASSERT(m_threadID);
49    return m_threadID;
50}
51
52void GCThread::initializeThreadID(ThreadIdentifier threadID)
53{
54    ASSERT(!m_threadID);
55    m_threadID = threadID;
56}
57
58SlotVisitor* GCThread::slotVisitor()
59{
60    ASSERT(m_slotVisitor);
61    return m_slotVisitor.get();
62}
63
64CopyVisitor* GCThread::copyVisitor()
65{
66    ASSERT(m_copyVisitor);
67    return m_copyVisitor.get();
68}
69
70GCPhase GCThread::waitForNextPhase()
71{
72    MutexLocker locker(m_shared.m_phaseLock);
73    while (m_shared.m_gcThreadsShouldWait)
74        m_shared.m_phaseCondition.wait(m_shared.m_phaseLock);
75
76    m_shared.m_numberOfActiveGCThreads--;
77    if (!m_shared.m_numberOfActiveGCThreads)
78        m_shared.m_activityCondition.signal();
79
80    while (m_shared.m_currentPhase == NoPhase)
81        m_shared.m_phaseCondition.wait(m_shared.m_phaseLock);
82    m_shared.m_numberOfActiveGCThreads++;
83    return m_shared.m_currentPhase;
84}
85
86void GCThread::gcThreadMain()
87{
88    GCPhase currentPhase;
89#if ENABLE(PARALLEL_GC)
90    WTF::registerGCThread();
91#endif
92    // Wait for the main thread to finish creating and initializing us. The main thread grabs this lock before
93    // creating this thread. We aren't guaranteed to have a valid threadID until the main thread releases this lock.
94    {
95        MutexLocker locker(m_shared.m_phaseLock);
96    }
97    {
98        ParallelModeEnabler enabler(*m_slotVisitor);
99        while ((currentPhase = waitForNextPhase()) != Exit) {
100            // Note: Each phase is responsible for its own termination conditions. The comments below describe
101            // how each phase reaches termination.
102            switch (currentPhase) {
103            case Mark:
104                m_slotVisitor->drainFromShared(SlotVisitor::SlaveDrain);
105                // GCThreads only return from drainFromShared() if the main thread sets the m_parallelMarkersShouldExit
106                // flag in the GCThreadSharedData. The only way the main thread sets that flag is if it realizes
107                // that all of the various subphases in Heap::markRoots() have been fully finished and there is
108                // no more marking work to do and all of the GCThreads are idle, meaning no more work can be generated.
109                break;
110            case Copy:
111                // We don't have to call startCopying() because it's called for us on the main thread to avoid a
112                // race condition.
113                m_copyVisitor->copyFromShared();
114                // We know we're done copying when we return from copyFromShared() because we would
115                // only do so if there were no more chunks of copying work left to do. When there is no
116                // more copying work to do, the main thread will wait in CopiedSpace::doneCopying() until
117                // all of the blocks that the GCThreads borrowed have been returned. doneCopying()
118                // returns our borrowed CopiedBlock, allowing the copying phase to finish.
119                m_copyVisitor->doneCopying();
120                break;
121            case NoPhase:
122                RELEASE_ASSERT_NOT_REACHED();
123                break;
124            case Exit:
125                RELEASE_ASSERT_NOT_REACHED();
126                break;
127            }
128        }
129    }
130}
131
132void GCThread::gcThreadStartFunc(void* data)
133{
134    GCThread* thread = static_cast<GCThread*>(data);
135    thread->gcThreadMain();
136}
137
138} // namespace JSC
139