[v8-dev] [v8] r15219 committed - Fix data race in v8::internal::UnboundQueue...

Wed, 19 Jun 2013 23:25:21 -0700 

Revision: 15219
Author:   [email protected]
Date:     Wed Jun 19 23:23:34 2013
Log:      Fix data race in v8::internal::UnboundQueue

This change modifies memory accesses to ensure proper load/store ordering.

BUG=249750
[email protected], [email protected]

Review URL: https://codereview.chromium.org/17294004
http://code.google.com/p/v8/source/detail?r=15219

Modified:
 /branches/bleeding_edge/src/cpu-profiler.cc
 /branches/bleeding_edge/src/optimizing-compiler-thread.cc
 /branches/bleeding_edge/src/unbound-queue-inl.h
 /branches/bleeding_edge/src/unbound-queue.h

=======================================
--- /branches/bleeding_edge/src/cpu-profiler.cc Mon Jun  3 02:46:32 2013
+++ /branches/bleeding_edge/src/cpu-profiler.cc Wed Jun 19 23:23:34 2013
@@ -191,9 +191,8 @@


 bool ProfilerEventsProcessor::ProcessCodeEvent(unsigned* dequeue_order) {
-  if (!events_buffer_.IsEmpty()) {
-    CodeEventsContainer record;
-    events_buffer_.Dequeue(&record);
+  CodeEventsContainer record;
+  if (events_buffer_.Dequeue(&record)) {
     switch (record.generic.type) {
 #define PROFILER_TYPE_CASE(type, clss)                          \
       case CodeEventRecord::type:                               \
=======================================
--- /branches/bleeding_edge/src/optimizing-compiler-thread.cc Mon Jun 3 08:32:22 2013 +++ /branches/bleeding_edge/src/optimizing-compiler-thread.cc Wed Jun 19 23:23:34 2013 
@@ -128,9 +128,8 @@
   ASSERT(!IsOptimizerThread());
   HandleScope handle_scope(isolate_);
   int functions_installed = 0;
-  while (!output_queue_.IsEmpty()) {
-    OptimizingCompiler* compiler;
-    output_queue_.Dequeue(&compiler);
+  OptimizingCompiler* compiler;
+  while (output_queue_.Dequeue(&compiler)) {
     Compiler::InstallOptimizedCode(compiler);
     functions_installed++;
   }
=======================================
--- /branches/bleeding_edge/src/unbound-queue-inl.h     Wed Jun 19 23:16:24 2013
+++ /branches/bleeding_edge/src/unbound-queue-inl.h     Wed Jun 19 23:23:34 2013
@@ -68,11 +68,12 @@


 template<typename Record>
-void UnboundQueue<Record>::Dequeue(Record* rec) {
-  ASSERT(divider_ != last_);
+bool UnboundQueue<Record>::Dequeue(Record* rec) {
+  if (divider_ == Acquire_Load(&last_)) return false;
   Node* next = reinterpret_cast<Node*>(divider_)->next;
   *rec = next->value;
   Release_Store(&divider_, reinterpret_cast<AtomicWord>(next));
+  return true;
 }


@@ -81,13 +82,22 @@
   Node*& next = reinterpret_cast<Node*>(last_)->next;
   next = new Node(rec);
   Release_Store(&last_, reinterpret_cast<AtomicWord>(next));
-  while (first_ != reinterpret_cast<Node*>(divider_)) DeleteFirst();
+
+  while (first_ != reinterpret_cast<Node*>(Acquire_Load(&divider_))) {
+    DeleteFirst();
+  }
 }


 template<typename Record>
-Record* UnboundQueue<Record>::Peek() {
-  ASSERT(divider_ != last_);
+bool UnboundQueue<Record>::IsEmpty() const {
+  return NoBarrier_Load(&divider_) == NoBarrier_Load(&last_);
+}
+
+
+template<typename Record>
+Record* UnboundQueue<Record>::Peek() const {
+  if (divider_ == Acquire_Load(&last_)) return NULL;
   Node* next = reinterpret_cast<Node*>(divider_)->next;
   return &next->value;
 }
=======================================
--- /branches/bleeding_edge/src/unbound-queue.h Thu May  5 23:50:20 2011
+++ /branches/bleeding_edge/src/unbound-queue.h Wed Jun 19 23:23:34 2013
@@ -46,10 +46,10 @@
   inline UnboundQueue();
   inline ~UnboundQueue();

-  INLINE(void Dequeue(Record* rec));
+  INLINE(bool Dequeue(Record* rec));
   INLINE(void Enqueue(const Record& rec));
-  INLINE(bool IsEmpty()) { return divider_ == last_; }
-  INLINE(Record* Peek());
+  INLINE(bool IsEmpty() const);
+  INLINE(Record* Peek() const);

  private:
   INLINE(void DeleteFirst());

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