From 3478ccc01b516a59a48272635d860d3beaa0dd93 Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Wed, 19 Jun 2013 10:18:18 +0000 Subject: call sched_yield repeatedly when terminating threads This should allow the threads we're terminating to more quickly enter a safe state where they're allowed to exit. On SMP systems, we need to yield the signalling thread more times to increase the probability the interrupted thread can run (and exit). --- thrpool.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/thrpool.c b/thrpool.c index a0c0bc2..7d62b59 100644 --- a/thrpool.c +++ b/thrpool.c @@ -66,6 +66,24 @@ void mog_thr_test_quit(void) } } +/* + * sched_yield may migrate us to the same CPU as the task we're waiting + * on, so just keep yielding for every CPU we have as this throttles + * our ability to spam SIGURG. This means the threads we're trying to + * gracefully kill off can finish their work and check their mog_do_quit + * flag sooner + */ +static void yield_all(void) +{ + static unsigned long nproc_all; + unsigned long i; + + if (!nproc_all) + nproc_all = num_processors(NPROC_ALL) * 2; + for (i = 0; i < nproc_all; i++) + pthread_yield(); +} + /* * we no longer rely on pthreads cancellation, so our explicit checks for * thread quitting requires us to continuously signal a thread for death @@ -81,7 +99,7 @@ static void poke(pthread_t thr, int sig) * we lower thread counts or shut down */ while ((err = pthread_kill(thr, sig)) == 0) - sched_yield(); + yield_all(); assert(err == ESRCH && "pthread_kill() usage bug"); } @@ -97,7 +115,7 @@ thr_create_fail_retry(struct mog_thrpool *tp, size_t size, syslog(LOG_ERR, "pthread_create: %m (tries: %lu)", *nr_eagain); } - sched_yield(); + yield_all(); return true; } else { errno = err; -- cgit v1.2.3-24-ge0c7