JavaScriptCore-1218.tar.gz

[apple/javascriptcore.git] / heap / GCThread.cpp

diff --git a/heap/GCThread.cpp b/heap/GCThread.cpp
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+/*
+ * Copyright (C) 2012 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "GCThread.h"
+
+#include "CopyVisitor.h"
+#include "CopyVisitorInlines.h"
+#include "GCThreadSharedData.h"
+#include "SlotVisitor.h"
+#include <wtf/MainThread.h>
+#include <wtf/PassOwnPtr.h>
+
+namespace JSC {
+
+GCThread::GCThread(GCThreadSharedData& shared, SlotVisitor* slotVisitor, CopyVisitor* copyVisitor)
+    : m_threadID(0)
+    , m_shared(shared)
+    , m_slotVisitor(WTF::adoptPtr(slotVisitor))
+    , m_copyVisitor(WTF::adoptPtr(copyVisitor))
+{
+}
+
+ThreadIdentifier GCThread::threadID()
+{
+    ASSERT(m_threadID);
+    return m_threadID;
+}
+
+void GCThread::initializeThreadID(ThreadIdentifier threadID)
+{
+    ASSERT(!m_threadID);
+    m_threadID = threadID;
+}
+
+SlotVisitor* GCThread::slotVisitor()
+{
+    ASSERT(m_slotVisitor);
+    return m_slotVisitor.get();
+}
+
+CopyVisitor* GCThread::copyVisitor()
+{
+    ASSERT(m_copyVisitor);
+    return m_copyVisitor.get();
+}
+
+GCPhase GCThread::waitForNextPhase()
+{
+    MutexLocker locker(m_shared.m_phaseLock);
+    while (m_shared.m_gcThreadsShouldWait)
+        m_shared.m_phaseCondition.wait(m_shared.m_phaseLock);
+
+    m_shared.m_numberOfActiveGCThreads--;
+    if (!m_shared.m_numberOfActiveGCThreads)
+        m_shared.m_activityCondition.signal();
+
+    while (m_shared.m_currentPhase == NoPhase)
+        m_shared.m_phaseCondition.wait(m_shared.m_phaseLock);
+    m_shared.m_numberOfActiveGCThreads++;
+    return m_shared.m_currentPhase;
+}
+
+void GCThread::gcThreadMain()
+{
+    GCPhase currentPhase;
+#if ENABLE(PARALLEL_GC)
+    WTF::registerGCThread();
+#endif
+    // Wait for the main thread to finish creating and initializing us. The main thread grabs this lock before 
+    // creating this thread. We aren't guaranteed to have a valid threadID until the main thread releases this lock.
+    {
+        MutexLocker locker(m_shared.m_phaseLock);
+    }
+    {
+        ParallelModeEnabler enabler(*m_slotVisitor);
+        while ((currentPhase = waitForNextPhase()) != Exit) {
+            // Note: Each phase is responsible for its own termination conditions. The comments below describe 
+            // how each phase reaches termination.
+            switch (currentPhase) {
+            case Mark:
+                m_slotVisitor->drainFromShared(SlotVisitor::SlaveDrain);
+                // GCThreads only return from drainFromShared() if the main thread sets the m_parallelMarkersShouldExit 
+                // flag in the GCThreadSharedData. The only way the main thread sets that flag is if it realizes 
+                // that all of the various subphases in Heap::markRoots() have been fully finished and there is 
+                // no more marking work to do and all of the GCThreads are idle, meaning no more work can be generated.
+                break;
+            case Copy:
+                // We don't have to call startCopying() because it's called for us on the main thread to avoid a 
+                // race condition.
+                m_copyVisitor->copyFromShared();
+                // We know we're done copying when we return from copyFromShared() because we would 
+                // only do so if there were no more chunks of copying work left to do. When there is no 
+                // more copying work to do, the main thread will wait in CopiedSpace::doneCopying() until 
+                // all of the blocks that the GCThreads borrowed have been returned. doneCopying() 
+                // returns our borrowed CopiedBlock, allowing the copying phase to finish.
+                m_copyVisitor->doneCopying();
+                break;
+            case NoPhase:
+                RELEASE_ASSERT_NOT_REACHED();
+                break;
+            case Exit:
+                RELEASE_ASSERT_NOT_REACHED();
+                break;
+            }
+        }
+    }
+}
+
+void GCThread::gcThreadStartFunc(void* data)
+{
+    GCThread* thread = static_cast<GCThread*>(data);
+    thread->gcThreadMain();
+}
+
+} // namespace JSC