Make |Heap::findGCInfo()| threadsafe.

Source/platform/heap/ThreadState.cpp

Index: Source/platform/heap/ThreadState.cpp
diff --git a/Source/platform/heap/ThreadState.cpp b/Source/platform/heap/ThreadState.cpp
index 87d0c40e847b614df6ebce10370292c8826cf9dc..3761aea84af0a8873aeb7c48d5c2525ed57d9275 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -96,7 +96,7 @@ uint8_t ThreadState::s_mainThreadStateStorage[sizeof(ThreadState)];
 SafePointBarrier* ThreadState::s_safePointBarrier = 0;
 bool ThreadState::s_inGC = false;
 
-static Mutex& threadAttachMutex()
+Mutex& ThreadState::threadAttachMutex()
 {
     AtomicallyInitializedStatic(Mutex&, mutex = *new Mutex);
     return mutex;
@@ -123,7 +123,7 @@ public:
         ASSERT(ThreadState::current()->isAtSafePoint());
 
         // Lock threadAttachMutex() to prevent threads from attaching.
-        threadAttachMutex().lock();
+        ThreadState::threadAttachMutex().lock();
 
         ThreadState::AttachedThreadStateSet& threads = ThreadState::attachedThreads();
 
@@ -182,7 +182,7 @@ public:
                 interruptors[i]->clearInterrupt();
         }
 
-        threadAttachMutex().unlock();
+        ThreadState::threadAttachMutex().unlock();
         ASSERT(ThreadState::current()->isAtSafePoint());
     }
 
@@ -315,7 +315,7 @@ void ThreadState::shutdown()
 void ThreadState::attachMainThread()
 {
     RELEASE_ASSERT(!Heap::s_shutdownCalled);
-    MutexLocker locker(threadAttachMutex());
+    MutexLocker locker(ThreadState::threadAttachMutex());
     ThreadState* state = new(s_mainThreadStateStorage) ThreadState();
     attachedThreads().add(state);
 }
@@ -331,7 +331,7 @@ void ThreadState::detachMainThread()
         state->enterSafePointWithoutPointers();
 
     {
-        MutexLocker locker(threadAttachMutex());
+        MutexLocker locker(ThreadState::threadAttachMutex());
         state->leaveSafePoint();
         ASSERT(attachedThreads().contains(state));
         attachedThreads().remove(state);
@@ -345,7 +345,7 @@ void ThreadState::shutdownHeapIfNecessary()
     // We don't need to enter a safe point before acquiring threadAttachMutex
     // because this thread is already detached.
 
-    MutexLocker locker(threadAttachMutex());
+    MutexLocker locker(ThreadState::threadAttachMutex());
     // We start shutting down the heap if there is no running thread
     // and Heap::shutdown() is already called.
     if (!attachedThreads().size() && Heap::s_shutdownCalled)
@@ -355,7 +355,7 @@ void ThreadState::shutdownHeapIfNecessary()
 void ThreadState::attach()
 {
     RELEASE_ASSERT(!Heap::s_shutdownCalled);
-    MutexLocker locker(threadAttachMutex());
+    MutexLocker locker(ThreadState::threadAttachMutex());
     ThreadState* state = new ThreadState();
     attachedThreads().add(state);
 }
@@ -397,7 +397,7 @@ void ThreadState::detach()
         state->enterSafePointWithoutPointers();
 
     {
-        MutexLocker locker(threadAttachMutex());
+        MutexLocker locker(ThreadState::threadAttachMutex());
         state->leaveSafePoint();
         ASSERT(attachedThreads().contains(state));
         attachedThreads().remove(state);
@@ -860,7 +860,7 @@ void ThreadState::addInterruptor(Interruptor* interruptor)
     SafePointScope scope(HeapPointersOnStack, SafePointScope::AllowNesting);
 
     {
-        MutexLocker locker(threadAttachMutex());
+        MutexLocker locker(ThreadState::threadAttachMutex());
         m_interruptors.append(interruptor);
     }
 }
@@ -870,7 +870,7 @@ void ThreadState::removeInterruptor(Interruptor* interruptor)
     SafePointScope scope(HeapPointersOnStack, SafePointScope::AllowNesting);
 
     {
-        MutexLocker locker(threadAttachMutex());
+        MutexLocker locker(ThreadState::threadAttachMutex());
         size_t index = m_interruptors.find(interruptor);
         RELEASE_ASSERT(index >= 0);
         m_interruptors.remove(index);