Fix data race in SamplingCircularQueue

test/cctest/test-circular-queue.cc

 // 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 24 matching lines @@
 
 
 TEST(SamplingCircularQueue) {
   typedef SamplingCircularQueue::Cell Record;
   const int kRecordsPerChunk = 4;
   SamplingCircularQueue scq(sizeof(Record),
                             kRecordsPerChunk * sizeof(Record),
                             3);
 
   // Check that we are using non-reserved values.
-  CHECK_NE(SamplingCircularQueue::kClear, 1);
-  CHECK_NE(SamplingCircularQueue::kEnd, 1);
   // Fill up the first chunk.
   CHECK_EQ(NULL, scq.StartDequeue());
   for (Record i = 1; i < 1 + kRecordsPerChunk; ++i) {
     Record* rec = reinterpret_cast<Record*>(scq.Enqueue());
     CHECK_NE(NULL, rec);
     *rec = i;
     CHECK_EQ(NULL, scq.StartDequeue());
   }
 
   // Fill up the second chunk. Consumption must still be unavailable.
@@ skipping 89 matching lines @@
   const int kRecordsPerChunk = 4;
   SamplingCircularQueue scq(sizeof(Record),
                             kRecordsPerChunk * sizeof(Record),
                             3);
   i::Semaphore* semaphore = i::OS::CreateSemaphore(0);
   // Don't poll ahead, making possible to check data in the buffer
   // immediately after enqueuing.
   scq.FlushResidualRecords();
 
   // Check that we are using non-reserved values.
-  CHECK_NE(SamplingCircularQueue::kClear, 1);
-  CHECK_NE(SamplingCircularQueue::kEnd, 1);
   ProducerThread producer1(&scq, kRecordsPerChunk, 1, semaphore);
   ProducerThread producer2(&scq, kRecordsPerChunk, 10, semaphore);
   ProducerThread producer3(&scq, kRecordsPerChunk, 20, semaphore);
 
   CHECK_EQ(NULL, scq.StartDequeue());
   producer1.Start();
   semaphore->Wait();
   for (Record i = 1; i < 1 + kRecordsPerChunk; ++i) {
     Record* rec = reinterpret_cast<Record*>(scq.StartDequeue());
     CHECK_NE(NULL, rec);
@@ skipping 24 matching lines @@
     CHECK_EQ(static_cast<int64_t>(i), static_cast<int64_t>(*rec));
     CHECK_EQ(rec, reinterpret_cast<Record*>(scq.StartDequeue()));
     scq.FinishDequeue();
     CHECK_NE(rec, reinterpret_cast<Record*>(scq.StartDequeue()));
   }
 
   CHECK_EQ(NULL, scq.StartDequeue());
 
   delete semaphore;
 }