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  1. Couchbase Server
  2. MB-19253

ep-engine: Benign data race on ExecutorThread::getTaskableName

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    • Untriaged
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    Description

      As reported by ThreadSanitizer (see below), there is a race between setting the current task associated with a ExecutorThread and reading the name of that thread.

      Unfortunately there doesn't seem to be a straightforward way to solve this without adding a new mutex; currentTask (the variable the race is on) is a SingleThreadedRCPtr, which is non-trivial to make thread-safe (i.e. atomic).

      ThreadSanitizer report:

          
      WARNING: ThreadSanitizer: data race (pid=27332)
      		 
            Read of size 8 at 0x7d340000c8f0 by main thread (mutexes: write M19366):
      		 
              #0 ExecutorThread::getTaskableName() const /home/couchbase/couchbase/ep-engine/src/atomic.h:309 (ep.so+0x0000000e6178)
      		 
              #1 EventuallyPersistentEngine::getStats(void const*, char const*, int, void (*)(char const*, unsigned short, char const*, unsigned int, void const*)) /home/couchbase/couchbase/ep-engine/src/ep_engine.cc:4346 (ep.so+0x0000000bc4dd)
      		 
              #2 EvpGetStats(engine_interface*, void const*, char const*, int, void (*)(char const*, unsigned short, char const*, unsigned int, void const*)) /home/couchbase/couchbase/ep-engine/src/ep_engine.cc:213 (ep.so+0x0000000ab49e)
      		 
              #3 mock_get_stats(engine_interface*, void const*, char const*, int, void (*)(char const*, unsigned short, char const*, unsigned int, void const*)) /home/couchbase/couchbase/memcached/programs/engine_testapp/engine_testapp.cc:239 (engine_testapp+0x0000004c54a
      		 
      d)
      		 
              #4 test_worker_stats(engine_interface*, engine_interface_v1*) /home/couchbase/couchbase/ep-engine/tests/ep_testsuite.cc:8901 (ep_testsuite.so+0x000000039768)
      		 
              #5 execute_test(test, char const*, char const*) /home/couchbase/couchbase/memcached/programs/engine_testapp/engine_testapp.cc:1090 (engine_testapp+0x0000004c40b2)
      		 
              #6 __libc_start_main /build/buildd/eglibc-2.15/csu/libc-start.c:226 (libc.so.6+0x00000002176c)
      		 
          
            Previous write of size 8 at 0x7d340000c8f0 by thread T5:
      		 
              #0 ExecutorThread::run() /home/couchbase/couchbase/ep-engine/src/atomic.h:322 (ep.so+0x0000000e9906)
      		 
              #1 launch_executor_thread(void*) /home/couchbase/couchbase/ep-engine/src/executorthread.cc:33 (ep.so+0x0000000e9795)
      		 
              #2 platform_thread_wrap /home/couchbase/.ccache/tmp/cb_pthread.tmp.00b591814417.18511.i (libplatform.so.0.1.0+0x000000003d91)

      Note: already fixed in Watson - see: http://review.couchbase.org/55829

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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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                Resolved:

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