Fix for issue 25236

runtime/vm/thread.cc

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/thread.h"
 
 #include "vm/dart_api_state.h"
 #include "vm/growable_array.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
@@ skipping 154 matching lines @@
 
 
 RawGrowableObjectArray* Thread::pending_functions() {
   if (pending_functions_ == GrowableObjectArray::null()) {
     pending_functions_ = GrowableObjectArray::New(Heap::kOld);
   }
   return pending_functions_;
 }
 
 
-void Thread::EnterIsolate(Isolate* isolate) {
+bool Thread::EnterIsolate(Isolate* isolate) {
   const bool kIsMutatorThread = true;
   const bool kDontBypassSafepoints = false;
   ThreadRegistry* tr = isolate->thread_registry();
   Thread* thread = tr->Schedule(
       isolate, kIsMutatorThread, kDontBypassSafepoints);
-  isolate->MakeCurrentThreadMutator(thread);
-  thread->set_vm_tag(VMTag::kVMTagId);
-  ASSERT(thread->store_buffer_block_ == NULL);
-  thread->StoreBufferAcquire();
+  if (thread != NULL) {
+    isolate->MakeCurrentThreadMutator(thread);
+    thread->set_vm_tag(VMTag::kVMTagId);
+    ASSERT(thread->store_buffer_block_ == NULL);
+    thread->StoreBufferAcquire();
+    return true;
+  }
+  return false;
 }
 
 
 void Thread::ExitIsolate() {
   Thread* thread = Thread::Current();
   ASSERT(thread != NULL);
   ASSERT(thread->IsMutatorThread());
 #if defined(DEBUG)
   ASSERT(!thread->IsAnyReusableHandleScopeActive());
 #endif  // DEBUG
   // Clear since GC will not visit the thread once it is unscheduled.
   thread->ClearReusableHandles();
   thread->StoreBufferRelease();
   Isolate* isolate = thread->isolate();
   ASSERT(isolate != NULL);
   if (isolate->is_runnable()) {
     thread->set_vm_tag(VMTag::kIdleTagId);
   } else {
     thread->set_vm_tag(VMTag::kLoadWaitTagId);
   }
   const bool kIsMutatorThread = true;
   const bool kDontBypassSafepoints = false;
   ThreadRegistry* tr = isolate->thread_registry();
   tr->Unschedule(thread, kIsMutatorThread, kDontBypassSafepoints);
   isolate->ClearMutatorThread();
 }
 
 
-void Thread::EnterIsolateAsHelper(Isolate* isolate, bool bypass_safepoint) {
+bool Thread::EnterIsolateAsHelper(Isolate* isolate, bool bypass_safepoint) {
   const bool kIsNotMutatorThread = false;
   ThreadRegistry* tr = isolate->thread_registry();
   Thread* thread = tr->Schedule(isolate, kIsNotMutatorThread, bypass_safepoint);
-  ASSERT(thread->store_buffer_block_ == NULL);
-  // TODO(koda): Use StoreBufferAcquire once we properly flush before Scavenge.
-  thread->store_buffer_block_ =
-      thread->isolate()->store_buffer()->PopEmptyBlock();
-  // This thread should not be the main mutator.
-  ASSERT(!thread->IsMutatorThread());
+  if (thread != NULL) {
+    ASSERT(thread->store_buffer_block_ == NULL);
+    // TODO(koda): Use StoreBufferAcquire once we properly flush
+    // before Scavenge.
+    thread->store_buffer_block_ =
+        thread->isolate()->store_buffer()->PopEmptyBlock();
+    // This thread should not be the main mutator.
+    ASSERT(!thread->IsMutatorThread());
+    return true;
+  }
+  return false;
 }
 
 
 void Thread::ExitIsolateAsHelper(bool bypass_safepoint) {
   Thread* thread = Thread::Current();
   ASSERT(thread != NULL);
   ASSERT(!thread->IsMutatorThread());
   thread->StoreBufferRelease();
   Isolate* isolate = thread->isolate();
   ASSERT(isolate != NULL);
@@ skipping 216 matching lines @@
 
 DisableThreadInterruptsScope::~DisableThreadInterruptsScope() {
   if (thread() != NULL) {
     OSThread* os_thread = thread()->os_thread();
     ASSERT(os_thread != NULL);
     os_thread->EnableThreadInterrupts();
   }
 }
 
 }  // namespace dart