Re: [Boost-users] thread lock-guard race condition

Subject: Re: [Boost-users] thread lock-guard race condition
From: Brian Budge (brian.budge_at_[hidden])
Date: 2010-11-25 00:00:01

If I recall, helgrind is not quite as fully-developed as the rest of
the valgrind suite, and I do think it can give false positives for
race conditions.

  Brian

On Wed, Nov 24, 2010 at 7:48 PM, Boost lzw <boostlzw_at_[hidden]> wrote:
> Hi, Phil,
>
> Valgrind user manual give no more information than " Applications that use
> the Boost.Thread library should run fine under DRD." I ran your code using
> DRD tool  of valgrind and got race warnings too.
>
> I then ran the following thread_group.cpp code distributed with boost_1_42,
> debugged it with valgrind --tool=drd, and it gave race warnings (more errors
> than your code) too:
>
> int count = 0;
> boost::mutex mutex;
>
> void increment_count()
> {
>     boost::mutex::scoped_lock lock(mutex);
>     std::cout << "count = " << ++count << std::endl;
> }
>
> int main(int argc, char* argv[])
> {
>     boost::thread_group threads;
>     for (int i = 0; i < 10; ++i)
>         threads.create_thread(&increment_count);
>     threads.join_all();
> }
>
> This suggests that valgrind might give false race warnings for boost thread
> code. Although I am not 100% sure of it. BTW, what other debugging tools are
> available to us for debugging boost threaded code?
>
> Robert
>
>
> On Wed, Nov 24, 2010 at 11:05 AM, Kraus Philipp <philipp.kraus_at_[hidden]>
> wrote:
>>
>> Hello,
>> I have written this little example:
>> boost::mutex mutex;
>> void thread()
>> {
>>     for (int i = 0; i < 5; ++i)
>>     {
>>         boost::this_thread::sleep(boost::posix_time::seconds(3));
>>         boost::lock_guard<boost::mutex> lock(mutex);
>>         std::cout << "Thread " << boost::this_thread::get_id() << ": " <<
>> i << std::endl;
>>     }
>> }
>> int main(int argc, char *argv[]) {
>>     boost::thread t1(thread);
>>     boost::thread t2(thread);
>>     t1.join();
>>     t2.join();
>> }
>> I compile the code with pthread option on the gcc (4.0.1). In the first
>> case the program works, but if I use the helgrind tool of valgrind I'll get
>> this errors (sorry for the long messages).
>> I would like to understand what I have done wrong. I hope I understand the
>> lock_guard in the correct way: If I create the lock with the mutex variable
>> the thread, that creates the lock runs down the next lines. All other
>> threads that run into the lock_guard line blocks until the lock variable of
>> the first thread call the destructor (which should be on every loop
>> iteration).
>> Thanks for help
>> Phil
>>
>> ------Valgrind Logs-----------
>>
>> ==19846== Thread #1 is the program's root thread
>> ==19846== Thread #3 & #2 was created
>> ==19846==    at 0x15A1FDE: __bsdthread_create (in
>> /usr/lib/libSystem.B.dylib)
>> ==19846==    by 0x378F4: pthread_create_WRK (hg_intercepts.c:257)
>> ==19846==    by 0x379C8: pthread_create (hg_intercepts.c:294)
>> ==19846==    by 0x55C06: boost::thread::start_thread() (in
>> libboost_thread.dylib)
>> ==19846==    by 0x9FED: boost::thread::thread<void (*)()>(void (*)(),
>> boost::disable_if<boost::is_convertible<void (*&)(),
>> boost::detail::thread_move_t<void (*)()> >, boost::thread::dummy*>::type)
>> (in ./main)
>> ==19846==    by 0x2A82: main (in ./main)
>> This message is show for thread #1, #2 and #3
>> ==19846== Possible data race during read of size 4 at 0x5e008 by thread #3
>> ==19846==    at 0x56381: void boost::call_once<void
>> (*)()>(boost::once_flag&, void (*)()) (in libboost_thread.dylib)
>> ==19846==    by 0x545AC: thread_proxy (in libboost_thread.dylib)
>> ==19846==    by 0x37828: mythread_wrapper (hg_intercepts.c:221)
>> ==19846==    by 0x15A2154: _pthread_start (in /usr/lib/libSystem.B.dylib)
>> ==19846==    by 0x15A2011: thread_start (in /usr/lib/libSystem.B.dylib)
>> ==19846==  This conflicts with a previous write of size 4 by thread #2
>> ==19846==    at 0x5647F: void boost::call_once<void
>> (*)()>(boost::once_flag&, void (*)()) (in /libboost_thread.dylib)
>> ==19846==    by 0x545AC: thread_proxy (in /libboost_thread.dylib)
>> ==19846==    by 0x37828: mythread_wrapper (hg_intercepts.c:221)
>> ==19846==    by 0x15A2154: _pthread_start (in /usr/lib/libSystem.B.dylib)
>> ==19846==    by 0x15A2011: thread_start (in /usr/lib/libSystem.B.dylib)
>> ==19846== Thread #2: Bug in libpthread: recursive write lock granted on
>> mutex/wrlock which does not support recursion
>> ==19846==    at 0x385D2: pthread_cond_timedwait_WRK (hg_intercepts.c:764)
>> ==19846==    by 0x386B0: pthread_cond_timedwait$* (hg_intercepts.c:798)
>> ==19846==    by 0x5AABB:
>> boost::condition_variable::timed_wait(boost::unique_lock<boost::mutex>&,
>> boost::posix_time::ptime const&) (in libboost_thread.dylib)
>> ==19846==    by 0x54DC5:
>> boost::this_thread::sleep(boost::posix_time::ptime const&) (in
>> libboost_thread.dylib)
>> ==19846==    by 0xEE31: void
>> boost::this_thread::sleep<boost::posix_time::seconds>(boost::posix_time::seconds
>> const&) (in ./main)
>> ==19846==    by 0x23F8: thread() (in ./main)
>> ==19846==    by 0x545CC: thread_proxy (in libboost_thread.dylib)
>> ==19846==    by 0x37828: mythread_wrapper (hg_intercepts.c:221)
>> ==19846==    by 0x15A2154: _pthread_start (in /usr/lib/libSystem.B.dylib)
>> ==19846==    by 0x15A2011: thread_start (in /usr/lib/libSystem.B.dylib)
>> The next message is shown for the thread #2 & #3
>> ==19846== Thread #3: lock order "0x2500668 before 0x25005C8" violated
>> ==19846==    at 0x37E1B: pthread_mutex_lock (hg_intercepts.c:496)
>> ==19846==    by 0x5ABA3:
>> boost::condition_variable::timed_wait(boost::unique_lock<boost::mutex>&,
>> boost::posix_time::ptime const&) (in libboost_thread.dylib)
>> ==19846==    by 0x54DC5:
>> boost::this_thread::sleep(boost::posix_time::ptime const&) (in
>> libboost_thread.dylib)
>> ==19846==    by 0xEE31: void
>> boost::this_thread::sleep<boost::posix_time::seconds>(boost::posix_time::seconds
>> const&) (in ./main)
>> ==19846==    by 0x23F8: thread() (in ./main)
>> ==19846==    by 0x545CC: thread_proxy (in libboost_thread.dylib)
>> ==19846==    by 0x37828: mythread_wrapper (hg_intercepts.c:221)
>> ==19846==    by 0x15A2154: _pthread_start (in /usr/lib/libSystem.B.dylib)
>> ==19846==    by 0x15A2011: thread_start (in /usr/lib/libSystem.B.dylib)
>> ==19846==   Required order was established by acquisition of lock at
>> 0x2500668
>> ==19846==    at 0x37E1B: pthread_mutex_lock (hg_intercepts.c:496)
>> ==19846==    by 0x15A3452: _pthread_cond_wait (in
>> /usr/lib/libSystem.B.dylib)
>> ==19846==    by 0x15C89F7: pthread_cond_timedwait$UNIX2003 (in
>> /usr/lib/libSystem.B.dylib)
>> ==19846==    by 0x38575: pthread_cond_timedwait_WRK (hg_intercepts.c:760)
>> ==19846==    by 0x386B0: pthread_cond_timedwait$* (hg_intercepts.c:798)
>> ==19846==    by 0x5AABB:
>> boost::condition_variable::timed_wait(boost::unique_lock<boost::mutex>&,
>> boost::posix_time::ptime const&) (in libboost_thread.dylib)
>> ==19846==    by 0x54DC5:
>> boost::this_thread::sleep(boost::posix_time::ptime const&) (in
>> libboost_thread.dylib)
>> ==19846==    by 0xEE31: void
>> boost::this_thread::sleep<boost::posix_time::seconds>(boost::posix_time::seconds
>> const&) (in ./main)
>> ==19846==    by 0x23F8: thread() (in ./main)
>> ==19846==    by 0x545CC: thread_proxy (in libboost_thread.dylib)
>> ==19846==    by 0x37828: mythread_wrapper (hg_intercepts.c:221)
>> ==19846==    by 0x15A2154: _pthread_start (in /usr/lib/libSystem.B.dylib)
>> ==19846==   followed by a later acquisition of lock at 0x25005C8
>> ==19846==    at 0x37E1B: pthread_mutex_lock (hg_intercepts.c:496)
>> ==19846==    by 0x53E6A: boost::this_thread::interruption_point() (in
>> libboost_thread.dylib)
>> ==19846==    by 0x5AAC2:
>> boost::condition_variable::timed_wait(boost::unique_lock<boost::mutex>&,
>> boost::posix_time::ptime const&) (in /libboost_thread.dylib)
>> ==19846==    by 0x54DC5:
>> boost::this_thread::sleep(boost::posix_time::ptime const&) (in
>> libboost_thread.dylib)
>> ==19846==    by 0xEE31: void
>> boost::this_thread::sleep<boost::posix_time::seconds>(boost::posix_time::seconds
>> const&) (in ./main)
>> ==19846==    by 0x23F8: thread() (in ./main)
>> ==19846==    by 0x545CC: thread_proxy (in libboost_thread.dylib)
>> ==19846==    by 0x37828: mythread_wrapper (hg_intercepts.c:221)
>> ==19846==    by 0x15A2154: _pthread_start (in /usr/lib/libSystem.B.dylib)
>> ==19846==    by 0x15A2011: thread_start (in /usr/lib/libSystem.B.dylib)
>>
>>
>>
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>
>
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