Fix for issue 26511 (VM hangs waiting for all threads that are not already at

runtime/vm/lockers.cc

 // Copyright (c) 2016, 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 "platform/assert.h"
 #include "vm/lockers.h"
 #include "vm/safepoint.h"
 
 namespace dart {
 
 
 static void updateThreadState(Thread* thread) {
   // First try a fast update of the thread state to indicate it is not at a
   // safepoint anymore.
-  uword old_state = Thread::SetAtSafepoint(true, 0);
+  uint32_t old_state = Thread::SetAtSafepoint(true, 0);
   uword addr =
       reinterpret_cast<uword>(thread) + Thread::safepoint_state_offset();
-  if (AtomicOperations::CompareAndSwapWord(
-          reinterpret_cast<uword*>(addr), old_state, 0) != old_state) {
+  if (AtomicOperations::CompareAndSwapUint32(
+          reinterpret_cast<uint32_t*>(addr), old_state, 0) != old_state) {
     // Fast update failed which means we could potentially be in the middle
     // of a safepoint operation and need to block for it.
     SafepointHandler* handler = thread->isolate()->safepoint_handler();
     handler->ExitSafepointUsingLock(thread);
   }
   thread->set_execution_state(Thread::kThreadInVM);
 }
 
 
 Monitor::WaitResult MonitorLocker::WaitWithSafepointCheck(Thread* thread,
                                                           int64_t millis) {
   ASSERT(thread == Thread::Current());
   thread->set_execution_state(Thread::kThreadInBlockedState);
   thread->EnterSafepoint();
   Monitor::WaitResult result = monitor_->Wait(millis);
   // First try a fast update of the thread state to indicate it is not at a
   // safepoint anymore.
-  uword old_state = Thread::SetAtSafepoint(true, 0);
+  uint32_t old_state = Thread::SetAtSafepoint(true, 0);
   uword addr =
       reinterpret_cast<uword>(thread) + Thread::safepoint_state_offset();
-  if (AtomicOperations::CompareAndSwapWord(
-          reinterpret_cast<uword*>(addr), old_state, 0) != old_state) {
+  if (AtomicOperations::CompareAndSwapUint32(
+          reinterpret_cast<uint32_t*>(addr), old_state, 0) != old_state) {
     // Fast update failed which means we could potentially be in the middle
     // of a safepoint operation and need to block for it.
     monitor_->Exit();
     SafepointHandler* handler = thread->isolate()->safepoint_handler();
     handler->ExitSafepointUsingLock(thread);
     monitor_->Enter();
   }
   thread->set_execution_state(Thread::kThreadInVM);
   return result;
 }
@@ skipping 39 matching lines @@
 
 
 Monitor::WaitResult SafepointMonitorLocker::Wait(int64_t millis) {
   Thread* thread = Thread::Current();
   if (thread != NULL) {
     thread->set_execution_state(Thread::kThreadInBlockedState);
     thread->EnterSafepoint();
     Monitor::WaitResult result = monitor_->Wait(millis);
     // First try a fast update of the thread state to indicate it is not at a
     // safepoint anymore.
-    uword old_state = Thread::SetAtSafepoint(true, 0);
+    uint32_t old_state = Thread::SetAtSafepoint(true, 0);
     uword addr =
         reinterpret_cast<uword>(thread) + Thread::safepoint_state_offset();
-    if (AtomicOperations::CompareAndSwapWord(
-            reinterpret_cast<uword*>(addr), old_state, 0) != old_state) {
+    if (AtomicOperations::CompareAndSwapUint32(
+            reinterpret_cast<uint32_t*>(addr), old_state, 0) != old_state) {
       // Fast update failed which means we could potentially be in the middle
       // of a safepoint operation and need to block for it.
       monitor_->Exit();
       SafepointHandler* handler = thread->isolate()->safepoint_handler();
       handler->ExitSafepointUsingLock(thread);
       monitor_->Enter();
     }
     thread->set_execution_state(Thread::kThreadInVM);
     return result;
   } else {
     return monitor_->Wait(millis);
   }
 }
 
 }  // namespace dart