Fix data race on Debug::thread_local_.current_debug_scope_

src/debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/api.h"
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 545 matching lines @@
   thread_local_.break_id_ = 0;
   thread_local_.break_frame_id_ = StackFrame::NO_ID;
   thread_local_.last_step_action_ = StepNone;
   thread_local_.last_statement_position_ = RelocInfo::kNoPosition;
   thread_local_.step_count_ = 0;
   thread_local_.last_fp_ = 0;
   thread_local_.queued_step_count_ = 0;
   thread_local_.step_into_fp_ = 0;
   thread_local_.step_out_fp_ = 0;
   // TODO(isolates): frames_are_dropped_?
-  thread_local_.current_debug_scope_ = NULL;
+  base::NoBarrier_Store(&thread_local_.current_debug_scope_,
+                        static_cast<base::AtomicWord>(NULL));
   thread_local_.restarter_frame_function_pointer_ = NULL;
 }
 
 
 char* Debug::ArchiveDebug(char* storage) {
   char* to = storage;
   MemCopy(to, reinterpret_cast<char*>(&thread_local_), sizeof(ThreadLocal));
   ThreadInit();
   return storage + ArchiveSpacePerThread();
 }
@@ skipping 2505 matching lines @@
 }
 
 
 DebugScope::DebugScope(Debug* debug)
     : debug_(debug),
       prev_(debug->debugger_entry()),
       save_(debug_->isolate_),
       no_termination_exceptons_(debug_->isolate_,
                                 StackGuard::TERMINATE_EXECUTION) {
   // Link recursive debugger entry.
-  debug_->thread_local_.current_debug_scope_ = this;
+  base::NoBarrier_Store(&debug_->thread_local_.current_debug_scope_,
+                        reinterpret_cast<base::AtomicWord>(this));
 
   // Store the previous break id and frame id.
   break_id_ = debug_->break_id();
   break_frame_id_ = debug_->break_frame_id();
 
   // Create the new break info. If there is no JavaScript frames there is no
   // break frame id.
   JavaScriptFrameIterator it(isolate());
   bool has_js_frames = !it.done();
   debug_->thread_local_.break_frame_id_ = has_js_frames ? it.frame()->id()
@@ skipping 16 matching lines @@
     // JavaScript. This can happen if the v8::Debug::Call is used in which
     // case the exception should end up in the calling code.
     if (!isolate()->has_pending_exception()) debug_->ClearMirrorCache();
 
     // If there are commands in the queue when leaving the debugger request
     // that these commands are processed.
     if (debug_->has_commands()) isolate()->stack_guard()->RequestDebugCommand();
   }
 
   // Leaving this debugger entry.
-  debug_->thread_local_.current_debug_scope_ = prev_;
+  base::NoBarrier_Store(&debug_->thread_local_.current_debug_scope_,
+                        reinterpret_cast<base::AtomicWord>(prev_));
 
   // Restore to the previous break state.
   debug_->thread_local_.break_frame_id_ = break_frame_id_;
   debug_->thread_local_.break_id_ = break_id_;
 
   debug_->UpdateState();
 }
 
 
 MessageImpl MessageImpl::NewEvent(DebugEvent event,
@@ skipping 242 matching lines @@
   logger_->DebugEvent("Put", message.text());
 }
 
 
 void LockingCommandMessageQueue::Clear() {
   base::LockGuard<base::Mutex> lock_guard(&mutex_);
   queue_.Clear();
 }
 
 } }  // namespace v8::internal