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

Subject: Re: [Boost-users] thread lock-guard race condition
From: Kraus Philipp (philipp.kraus_at_[hidden])
Date: 2010-11-25 04:12:24

Hi Robert,

Am 25.11.2010 um 04:48 schrieb Boost lzw:

> 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:

Yes, the same things here. I tested the code with Boost 1.44 and 1.45  
on OSX and Gentoo Linux. }

> This suggests that valgrind might give false race warnings for boost  
> thread code. Although I am not 100% sure of it.

If there are only false-positivies, I would ignore this error. I think  
so, because the code works fine and in my data structures are no errors

Thx

Phil

>
> 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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