setitimer vs. threads: SIGALRM returned to which thread? (process master or individual child)
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From: Davide Libenzi on 11 Apr 2010 18:10 On Sun, 11 Apr 2010, Andi Kleen wrote: > "Frantisek Rysanek" <Frantisek.Rysanek(a)post.cz> writes: > > > Yes, it used to be quite a relief to have Linux do the management of > > timers for me. Now I have two options to choose from: > > 1) write my own "timer queueing" (timekeeping) code to order the > > timers for me in the master thread > > 2) find another function, similar to setitimer(), that would function > > the way setitimer() used to work in the old days... > > POSIX timers (timer_create et.al.) allow specifying the signal. > > So if you use custom RT signals for each threads and block them in the > threads you don't want them it should work. This would limit the > maximum number of threads though because there's only a limited > range of RT signals. > > There are probably other ways to do this too, e.g. with some clever > use of timerfd_create in recent kernels. Definitely timerfd allows you to handle the timer event wherever you like, independently from signals. Much much simpler routing. But if you need to be compatible with multiple unixes, of even older linux kernel, you are out of luck with timerfd. - Davide -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Thomas Gleixner on 11 Apr 2010 18:20
On Sun, 11 Apr 2010, Andi Kleen wrote: > "Frantisek Rysanek" <Frantisek.Rysanek(a)post.cz> writes: > > > Yes, it used to be quite a relief to have Linux do the management of > > timers for me. Now I have two options to choose from: > > 1) write my own "timer queueing" (timekeeping) code to order the > > timers for me in the master thread > > 2) find another function, similar to setitimer(), that would function > > the way setitimer() used to work in the old days... > > POSIX timers (timer_create et.al.) allow specifying the signal. > > So if you use custom RT signals for each threads and block them in the > threads you don't want them it should work. This would limit the > maximum number of threads though because there's only a limited > range of RT signals. > > There are probably other ways to do this too, e.g. with some clever > use of timerfd_create in recent kernels. > > Or you could overwrite the clone in the thread library to not > set signal sharing semantics. This might have other bad side effects > though. Nonsense. Just use the right flags when creating the posix timer. posix timers support per thread delivery of a signal, i.e. you can use the same signal for all threads. sigev.sigev_notify = SIGEV_THREAD_ID | SIGEV_SIGNAL; sigev.sigev_signo = YOUR_SIGNAL; sigev.sigev_notify_thread_id = gettid(); timer_create(CLOCK_MONOTONIC, &sigev, &timer); That signal for that timer will not be delivered to any other thread than the one specified in sigev.sigev_notify_thread_id as long as that thread has not exited w/o canceling the timer. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |