Status: New
Owner: ----
New issue 3160 by [email protected]: Data race between Thread::Join() and
ThreadEntry()
http://code.google.com/p/v8/issues/detail?id=3160
/usr/local/google/v8-bleeding/out/x64.release/cctest
test-cpu-profiler/CodeEvents --nobreak-on-abort --nofold-constants
--testing_serialization_file=/usr/local/google/v8-bleeding/out/.serdes/serdes_CodeEvents
==================
WARNING: ThreadSanitizer: data race (pid=15477)
Read of size 8 at 0x7d040000b770 by main thread:
#0 v8::internal::Thread::Join()
/usr/local/google/v8-bleeding/out/../src/platform-posix.cc:652
(cctest+0x00000121fb82)
#1 v8::internal::ProfilerEventsProcessor::StopSynchronously()
/usr/local/google/v8-bleeding/out/../src/cpu-profiler.cc:83
(cctest+0x000000cb77f6)
#2 TestCodeEvents()
/usr/local/google/v8-bleeding/out/../test/cctest/test-cpu-profiler.cc:164
(cctest+0x000000aef33c)
#3 CcTest::Run()
/usr/local/google/v8-bleeding/out/../test/cctest/cctest.cc:83
(cctest+0x000000a19f4b)
#4 main /usr/local/google/v8-bleeding/out/../test/cctest/cctest.cc:178
(cctest+0x000000a1a489)
Previous write of size 8 at 0x7d040000b770 by thread T6:
[failed to restore the stack]
Location is heap block of size 8 at 0x7d040000b770 allocated by main
thread:
#0 malloc
/usr/local/google/asan/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:469
(cctest+0x0000009b702d)
#1 v8::internal::Malloced::New(unsigned long)
/usr/local/google/v8-bleeding/out/../src/allocation.cc:43
(cctest+0x000000c13fc5)
#2 operator new
/usr/local/google/v8-bleeding/out/../src/allocation.h:44
(cctest+0x00000121f8b0)
#3 v8::internal::Thread::Thread(v8::internal::Thread::Options const&)
/usr/local/google/v8-bleeding/out/../src/platform-posix.cc:570
(cctest+0x00000121f8b0)
#4
v8::internal::ProfilerEventsProcessor::ProfilerEventsProcessor(v8::internal::ProfileGenerator*,
v8::internal::Sampler*, v8::internal::TimeDelta)
/usr/local/google/v8-bleeding/out/../src/cpu-profiler.cc:55
(cctest+0x000000cb71af)
#5 TestCodeEvents()
/usr/local/google/v8-bleeding/out/../test/cctest/test-cpu-profiler.cc:144
(cctest+0x000000aef0e8)
#6 CcTest::Run()
/usr/local/google/v8-bleeding/out/../test/cctest/cctest.cc:83
(cctest+0x000000a19f4b)
#7 main /usr/local/google/v8-bleeding/out/../test/cctest/cctest.cc:178
(cctest+0x000000a1a489)
Thread T6 'v8:ProfEvntProc' (tid=15484, running) created by main thread
at:
#0 pthread_create
/usr/local/google/asan/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:865
(cctest+0x0000009baee6)
#1 v8::internal::Thread::Start()
/usr/local/google/v8-bleeding/out/../src/platform-posix.cc:642
(cctest+0x00000121fabc)
#2 TestCodeEvents()
/usr/local/google/v8-bleeding/out/../test/cctest/test-cpu-profiler.cc:146
(cctest+0x000000aef0f0)
#3 CcTest::Run()
/usr/local/google/v8-bleeding/out/../test/cctest/cctest.cc:83
(cctest+0x000000a19f4b)
#4 main /usr/local/google/v8-bleeding/out/../test/cctest/cctest.cc:178
(cctest+0x000000a1a489)
SUMMARY: ThreadSanitizer: data race
/usr/local/google/v8-bleeding/out/../src/platform-posix.cc:652
v8::internal::Thread::Join()
================================================
Despite the previous write stack is missing, I can tell that's the write of
pthread_self() into thread->data()->thread_ in ThreadEntry()
(src/platform-posix.cc) - the report disappears when I remove that write.
This write isn't synchronized with accesses to thread_ from other threads
(including the write performed by pthread_create() in the parent thread),
so it may be dangerous for a third thread to read thread_ before the caller
of pthread_create() has returned. This makes the value of
thread->data()->thread_ written in ThreadEntry() only useful in the child
thread that performs ThreadEntry() - but there's pthread_self() for that,
maybe use it instead?
One may also possibly imagine a pthread_create implementation (or a
compiler optimization of NPTL, Linuxthreads or Bionic threads) that assumes
nobody is writing to the first parameter (e.g. it may re-read that from
memory).
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