Make NoReloadScope thread safe

runtime/vm/isolate.cc

 // Copyright (c) 2013, 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/isolate.h"
 
 #include "include/dart_api.h"
 #include "include/dart_native_api.h"
 #include "platform/assert.h"
 #include "platform/text_buffer.h"
+#include "vm/atomic.h"
 #include "vm/class_finalizer.h"
 #include "vm/code_observers.h"
 #include "vm/compiler.h"
 #include "vm/compiler_stats.h"
 #include "vm/dart_api_message.h"
 #include "vm/dart_api_state.h"
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/deopt_instructions.h"
 #include "vm/flags.h"
@@ skipping 114 matching lines @@
 NoOOBMessageScope::NoOOBMessageScope(Thread* thread) : StackResource(thread) {
   thread->DeferOOBMessageInterrupts();
 }
 
 
 NoOOBMessageScope::~NoOOBMessageScope() {
   thread()->RestoreOOBMessageInterrupts();
 }
 
 
-
 NoReloadScope::NoReloadScope(Isolate* isolate, Thread* thread)
     : StackResource(thread),
       isolate_(isolate) {
   ASSERT(isolate_ != NULL);
-  isolate_->no_reload_scope_depth_++;
-  ASSERT(isolate_->no_reload_scope_depth_ >= 0);
+  AtomicOperations::FetchAndIncrement(&(isolate_->no_reload_scope_depth_));
 }
 
 
 NoReloadScope::~NoReloadScope() {
-  isolate_->no_reload_scope_depth_--;
-  ASSERT(isolate_->no_reload_scope_depth_ >= 0);
+  uintptr_t previous_value =
+      AtomicOperations::FetchAndDecrement(&(isolate_->no_reload_scope_depth_));
+  // If the previous value was 0 we have underflowed.
+  ASSERT(previous_value != 0);
 }
 
 
 void Isolate::RegisterClass(const Class& cls) {
   NOT_IN_PRODUCT(
     if (IsReloading()) {
       reload_context()->RegisterClass(cls);
       return;
     }
   )
@@ skipping 899 matching lines @@
     }
     lib.InitExportedNamesCache();
   }
   TokenStream::CloseSharedTokenList(this);
 }
 
 
 bool Isolate::CanReload() const {
 #ifndef PRODUCT
   return !ServiceIsolate::IsServiceIsolateDescendant(this) &&
-         is_runnable() && !IsReloading() && (no_reload_scope_depth_ == 0) &&
+         is_runnable() && !IsReloading() &&
+         (AtomicOperations::LoadRelaxed(&no_reload_scope_depth_) == 0) &&
          IsolateCreationEnabled();
 #else
   return false;
 #endif
 }
 
 
 #ifndef PRODUCT
 bool Isolate::ReloadSources(JSONStream* js,
                             bool force_reload,
@@ skipping 1805 matching lines @@
 void IsolateSpawnState::DecrementSpawnCount() {
   ASSERT(spawn_count_monitor_ != NULL);
   ASSERT(spawn_count_ != NULL);
   MonitorLocker ml(spawn_count_monitor_);
   ASSERT(*spawn_count_ > 0);
   *spawn_count_ = *spawn_count_ - 1;
   ml.Notify();
 }
 
 }  // namespace dart