Hi! > > Hmm, so you did hit the small window for race condition between the new > > thread signals the main thread that it's executed and the next call to > > the mutex_lock on the tested mutex? > > Yes, I'm assuming this is reason why I see it sporadically failing on > different distros/kernels. I see it happening the most on IBM z/VM (s390) > guests which have overcommitted resources, which affects scheduling. > > It takes longer, but I could trigger it on x86_64 too.
I think that I know where the problem may come from. We are starting the threads in reverse order by priority, so the lowest one can actually be preempted by the higher priority one before the lock is taken, which makes sense. > > I do not like this solution much, but this is not easy to do properly. > > One posibility is to pinpoint the threads on one cpu via the affinity() > > interface (open_posix_testsuite/include/affinity.h) then we can wait in > > the main thread until the thread with lowest priority is executed and > > safely say that the rest is locked on the mutex allready (as they run > > with FIFO scheduling). > > I was considering this too, but there are some problems: > > 1. pthread_setaffinity_np is not portable / sched_setaffinity is Linux only This is the reason we have the open_posix_testsuite/include/affinity.h, it's not portable but some test cannot be written without it and it's implemented on most POSIX OSes, so we keep the unportable chunks in one place. > 2. linux default sched_rt_runtime_us gives 0.05s to be used by > SCHED_OTHER (non-RT tasks) (Documentation/scheduler/sched-rt-group.txt) > If we set also main thread to use SCHED_FIFO, then this shouldn't be > problem. That shouldn't be much of problem, the main thread would pick up once the realtime threads are locked on mutexes/cond vars. Or am I mistaken here? -- Cyril Hrubis [email protected] ------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk _______________________________________________ Ltp-list mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/ltp-list
