Oilpan: simplify away StoppingOtherThreads pseudo GCState.

Source/platform/heap/ThreadState.cpp

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 708 matching lines @@
 
 #define UNEXPECTED_GCSTATE(s) case ThreadState::s: RELEASE_ASSERT_WITH_MESSAGE(false, "Unexpected transition while in GCState " #s); return
 
 void unexpectedGCState(ThreadState::GCState gcState)
 {
     switch (gcState) {
         UNEXPECTED_GCSTATE(NoGCScheduled);
         UNEXPECTED_GCSTATE(IdleGCScheduled);
         UNEXPECTED_GCSTATE(PreciseGCScheduled);
         UNEXPECTED_GCSTATE(FullGCScheduled);
-        UNEXPECTED_GCSTATE(StoppingOtherThreads);
         UNEXPECTED_GCSTATE(GCRunning);
         UNEXPECTED_GCSTATE(EagerSweepScheduled);
         UNEXPECTED_GCSTATE(LazySweepScheduled);
         UNEXPECTED_GCSTATE(Sweeping);
         UNEXPECTED_GCSTATE(SweepingAndIdleGCScheduled);
         UNEXPECTED_GCSTATE(SweepingAndPreciseGCScheduled);
     default:
         ASSERT_NOT_REACHED();
         return;
     }
 }
 
 #undef UNEXPECTED_GCSTATE
 
 } // namespace
 
 #define VERIFY_STATE_TRANSITION(condition) if (UNLIKELY(!(condition))) unexpectedGCState(m_gcState)
 
 void ThreadState::setGCState(GCState gcState)
 {
     switch (gcState) {
     case NoGCScheduled:
         checkThread();
-        VERIFY_STATE_TRANSITION(m_gcState == StoppingOtherThreads || m_gcState == Sweeping || m_gcState == SweepingAndIdleGCScheduled);
+        VERIFY_STATE_TRANSITION(m_gcState == Sweeping || m_gcState == SweepingAndIdleGCScheduled);
         break;
     case IdleGCScheduled:
     case PreciseGCScheduled:
     case FullGCScheduled:
         checkThread();
-        VERIFY_STATE_TRANSITION(m_gcState == NoGCScheduled || m_gcState == IdleGCScheduled || m_gcState == PreciseGCScheduled || m_gcState == FullGCScheduled || m_gcState == StoppingOtherThreads || m_gcState == SweepingAndIdleGCScheduled || m_gcState == SweepingAndPreciseGCScheduled);
+        VERIFY_STATE_TRANSITION(m_gcState == NoGCScheduled || m_gcState == IdleGCScheduled || m_gcState == PreciseGCScheduled || m_gcState == FullGCScheduled || m_gcState == SweepingAndIdleGCScheduled || m_gcState == SweepingAndPreciseGCScheduled);
         completeSweep();
         break;
-    case StoppingOtherThreads:
-        checkThread();
-        VERIFY_STATE_TRANSITION(m_gcState == NoGCScheduled || m_gcState == IdleGCScheduled || m_gcState == PreciseGCScheduled || m_gcState == FullGCScheduled || m_gcState == Sweeping || m_gcState == SweepingAndIdleGCScheduled || m_gcState == SweepingAndPreciseGCScheduled);
-        break;
     case GCRunning:
         ASSERT(!isInGC());
         VERIFY_STATE_TRANSITION(m_gcState != GCRunning);
         break;
     case EagerSweepScheduled:
     case LazySweepScheduled:
         ASSERT(isInGC());
         VERIFY_STATE_TRANSITION(m_gcState == GCRunning);
         break;
     case Sweeping:
         checkThread();
-        VERIFY_STATE_TRANSITION(m_gcState == StoppingOtherThreads || m_gcState == EagerSweepScheduled || m_gcState == LazySweepScheduled);
+        VERIFY_STATE_TRANSITION(m_gcState == EagerSweepScheduled || m_gcState == LazySweepScheduled);
         break;
     case SweepingAndIdleGCScheduled:
     case SweepingAndPreciseGCScheduled:
         checkThread();
-        VERIFY_STATE_TRANSITION(m_gcState == StoppingOtherThreads || m_gcState == Sweeping || m_gcState == SweepingAndIdleGCScheduled || m_gcState == SweepingAndPreciseGCScheduled);
+        VERIFY_STATE_TRANSITION(m_gcState == Sweeping || m_gcState == SweepingAndIdleGCScheduled || m_gcState == SweepingAndPreciseGCScheduled);
         break;
     default:
         ASSERT_NOT_REACHED();
     }
     m_gcState = gcState;
 }
 
 #undef VERIFY_STATE_TRANSITION
 
 ThreadState::GCState ThreadState::gcState() const
@@ skipping 11 matching lines @@
         Heap::setEstimatedLiveObjectSize(Heap::estimatedLiveObjectSize() / 2);
     }
 }
 
 void ThreadState::runScheduledGC(StackState stackState)
 {
     checkThread();
     if (stackState != NoHeapPointersOnStack)
         return;
 
+    // If a safe point is entered while initiating a GC, we clearly do
+    // not want to do another as part that -- the safe point is only
+    // entered after checking if a scheduled GC ought to run first.
+    // Prevent that from happening by marking GCs as forbidden while
+    // one is initiated and later running.
+    if (isGCForbidden())
+        return;
+
     switch (gcState()) {
     case FullGCScheduled:
         Heap::collectAllGarbage();
         break;
     case PreciseGCScheduled:
         Heap::collectGarbage(NoHeapPointersOnStack, GCWithoutSweep, Heap::PreciseGC);
         break;
     case IdleGCScheduled:
         // Idle time GC will be scheduled by Blink Scheduler.
         break;
@@ skipping 279 matching lines @@
 #endif
 
 void ThreadState::enterSafePoint(StackState stackState, void* scopeMarker)
 {
     checkThread();
 #ifdef ADDRESS_SANITIZER
     if (stackState == HeapPointersOnStack)
         scopeMarker = adjustScopeMarkerForAdressSanitizer(scopeMarker);
 #endif
     ASSERT(stackState == NoHeapPointersOnStack || scopeMarker);
-    ASSERT(!isGCForbidden());
     runScheduledGC(stackState);
     ASSERT(!m_atSafePoint);
     m_atSafePoint = true;
     m_stackState = stackState;
     m_safePointScopeMarker = scopeMarker;
     s_safePointBarrier->enterSafePoint(this);
 }
 
 void ThreadState::leaveSafePoint(SafePointAwareMutexLocker* locker)
 {
@@ skipping 228 matching lines @@
         json->beginArray(it->key.ascii().data());
         for (size_t age = 0; age <= maxHeapObjectAge; ++age)
             json->pushInteger(it->value.ages[age]);
         json->endArray();
     }
     TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(TRACE_DISABLED_BY_DEFAULT("blink_gc"), statsName, this, json.release());
 }
 #endif
 
 } // namespace blink