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  1. Couchbase Server
  2. MB-19252

ep-engine: data races in Stream::readyQueueMemory

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    Description

      As detected by TSan. This variable is only used to generate stream statistics, so the impact of it being incorrect should be limited to the %s:stream_%d_ready_queue_memory stream stat.

      WARNING: ThreadSanitizer: data race (pid=17244)
      		 
        Read of size 8 at 0x7d480000b370 by main thread (mutexes: write M24165, write M969, read M24121):
      		 
          #0 Stream::getReadyQueueMemory() /home/daver/repos/couchbase/server/ep-engine/src/dcp-stream.cc:234 (ep.so+0x00000028f51e)
      		 
          #1 ActiveStream::addStats(void (*)(char const*, unsigned short, char const*, unsigned int, void const*), void const*) /home/daver/repos/couchbase/server/ep-engine/src/dcp-stream.cc:563 (ep.so+0x00000029452f)
      		 
          #2 DcpProducer::addStats(void (*)(char const*, unsigned short, char const*, unsigned int, void const*), void const*) /home/daver/repos/couchbase/server/ep-engine/src/dcp-producer.cc:551 (ep.so+0x00000027f1a0)
      		 
          #3 ConnStatBuilder::operator()(SingleThreadedRCPtr<ConnHandler>&) /home/daver/repos/couchbase/server/ep-engine/src/ep_engine.cc:3696 (ep.so+0x000000182d54)
      		 
       
      		 
        Previous write of size 8 at 0x7d480000b370 by thread T16 (mutexes: write M24143):
      		 
          #0 Stream::pushToReadyQ(DcpResponse*) /home/daver/repos/couchbase/server/ep-engine/src/dcp-stream.cc:211 (ep.so+0x00000028f4a6)
      		 
          #1 ActiveStream::backfillReceived(Item*) /home/daver/repos/couchbase/server/ep-engine/src/dcp-stream.cc:407 (ep.so+0x00000028d6e5)
      		 
          #2 CacheCallback::callback(CacheLookup&) /home/daver/repos/couchbase/server/ep-engine/src/dcp-stream.cc:87 (ep.so+0x00000028d4b3)
      		 
          #3 CouchKVStore::recordDbDump(_db*, _docinfo*, void*) /home/daver/repos/couchbase/server/ep-engine/src/couch-kvstore/couch-kvstore.cc:1563 (ep.so+0x00000031dec5)

      Note: Already fixed in watson: http://review.couchbase.org/54314:

      We are also not acquiring lock in the function getReadyQueueMemory. Given that it is just a read instead of acquiring the streamMutex lock, the readyQueueMemory variable can be made an atomic.

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          Task - A task that needs to be done. MB-19323 3.1.6 release

          • Major - Major loss of function.
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              drigby Dave Rigby (Inactive)
              drigby Dave Rigby (Inactive)
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