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

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 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 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_guardboost::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 (*)(), boost::disable_if >, 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(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(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$* (hg_intercepts.c:798) ==19846==    by 0x5AABB: boost::condition_variable::timed_wait(boost::unique_lockboost::mutex&, boost::posix_time::ptime const&) (in libboost_thread.dylib) ==19846==    by 0x54DC5: boost::this_thread::sleep(boost::posix_time::ptime const&) (in libboost_thread.dylib) ==19846==    by 0xEE31: void boost::this_thread::sleepboost::posix_time::seconds(boost::posix_time::seconds const&) (in ./main) ==19846==    by 0x23F8: thread() (in ./main) ==19846==    by 0x545CC: thread_proxy (in libboost_thread.dylib) ==19846==    by 0x37828: mythread_wrapper (hg_intercepts.c:221) ==19846==    by 0x15A2154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==19846==    by 0x15A2011: thread_start (in /usr/lib/libSystem.B.dylib) The next message is shown for the thread #2 & #3 ==19846== Thread #3: lock order "0x2500668 before 0x25005C8" violated ==19846==    at 0x37E1B: pthread_mutex_lock (hg_intercepts.c:496) ==19846==    by 0x5ABA3: boost::condition_variable::timed_wait(boost::unique_lockboost::mutex&, boost::posix_time::ptime const&) (in libboost_thread.dylib) ==19846==    by 0x54DC5: boost::this_thread::sleep(boost::posix_time::ptime const&) (in libboost_thread.dylib) ==19846==    by 0xEE31: void boost::this_thread::sleepboost::posix_time::seconds(boost::posix_time::seconds const&) (in ./main) ==19846==    by 0x23F8: thread() (in ./main) ==19846==    by 0x545CC: thread_proxy (in libboost_thread.dylib) ==19846==    by 0x37828: mythread_wrapper (hg_intercepts.c:221) ==19846==    by 0x15A2154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==19846==    by 0x15A2011: thread_start (in /usr/lib/libSystem.B.dylib) ==19846==   Required order was established by acquisition of lock at 0x2500668 ==19846==    at 0x37E1B: pthread_mutex_lock (hg_intercepts.c:496) ==19846==    by 0x15A3452: _pthread_cond_wait (in /usr/lib/libSystem.B.dylib) ==19846==    by 0x15C89F7: pthread_cond_timedwait$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_lockboost::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::sleepboost::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_lockboost::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::sleepboost::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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