Add multithreading test for SamplingCircularQueue, fix implementation.

src/circular-queue.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 58 matching lines @@
 // possible that it can catch up and overwrite a chunk that a consumer
 // is currently reading, resulting in a corrupt record being read.
 class SamplingCircularQueue {
  public:
   // Executed on the application thread.
   SamplingCircularQueue(int record_size_in_bytes,
                         int desired_chunk_size_in_bytes,
                         int buffer_size_in_chunks);
   ~SamplingCircularQueue();
 
-  // Executed on the producer (sampler) or application thread.
-  void SetUpProducer();
   // Enqueue returns a pointer to a memory location for storing the next
   // record.
   INLINE(void* Enqueue());
-  void TearDownProducer();
 
   // Executed on the consumer (analyzer) thread.
-  void SetUpConsumer();
   // StartDequeue returns a pointer to a memory location for retrieving
   // the next record. After the record had been read by a consumer,
   // FinishDequeue must be called. Until that moment, subsequent calls
   // to StartDequeue will return the same pointer.
   void* StartDequeue();
   void FinishDequeue();
   // Due to a presence of slipping between the producer and the consumer,
   // the queue must be notified whether producing has been finished in order
   // to process remaining records from the buffer.
   void FlushResidualRecords();
-  void TearDownConsumer();
 
   typedef AtomicWord Cell;
   // Reserved values for the first cell of a record.
   static const Cell kClear = 0;  // Marks clean (processed) chunks.
   static const Cell kEnd = -1;   // Marks the end of the buffer.
 
  private:
+  struct ProducerPosition {
+    Cell* enqueue_pos;
+  };
   struct ConsumerPosition {
     Cell* dequeue_chunk_pos;
     Cell* dequeue_chunk_poll_pos;
     Cell* dequeue_pos;
     Cell* dequeue_end_pos;
   };
 
   INLINE(void WrapPositionIfNeeded(Cell** pos));
 
   const int record_size_;
   const int chunk_size_in_bytes_;
   const int chunk_size_;
   const int buffer_size_;
   const int producer_consumer_distance_;
   Cell* buffer_;
-  // Store producer and consumer data in TLS to avoid modifying the
-  // same CPU cache line from two threads simultaneously.
-  Thread::LocalStorageKey consumer_key_;
-  Thread::LocalStorageKey producer_key_;
+  byte* positions_;
+  ProducerPosition* producer_pos_;
+  ConsumerPosition* consumer_pos_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_CIRCULAR_QUEUE_H_