From af409e4bdfa25bbab911a706a9f123d98be54c23 Mon Sep 17 00:00:00 2001 From: Ivan Maidanski Date: Fri, 17 Nov 2017 21:32:40 +0300 Subject: [PATCH] Workaround hangs in sigsuspend and sem_wait if compiled with TSan Issue #181 (bdwgc). * pthread_stop_world.c [!GC_OPENBSD_UTHREADS && !NACL && THREAD_SANITIZER] (GC_suspend_handler_inner): Call pthread_sigmask(SIG_SETMASK) with an empty set (thus unmask all signals); add comment. * pthread_stop_world.c [!GC_OPENBSD_UTHREADS && !NACL && THREAD_SANITIZER] (GC_stop_world): Call sem_trywait() repeatedly (with a delay of 100 microseconds) while getting EAGAIN error (instead of a sem_wait call). --- pthread_stop_world.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/pthread_stop_world.c b/pthread_stop_world.c index cfb4c1ae8..0f965726b 100644 --- a/pthread_stop_world.c +++ b/pthread_stop_world.c @@ -310,6 +310,16 @@ STATIC void GC_suspend_handler_inner(ptr_t dummy GC_ATTR_UNUSED, me -> backing_store_ptr = GC_save_regs_in_stack(); # endif +# ifdef THREAD_SANITIZER + /* TSan disables signals around signal handlers. */ + { + sigset_t set; + sigemptyset(&set); + if (pthread_sigmask(SIG_SETMASK, &set, NULL) != 0) + ABORT("pthread_sigmask(SIG_SETMASK) failed"); + } +# endif + /* Tell the thread that wants to stop the world that this */ /* thread has been stopped. Note that sem_post() is */ /* the only async-signal-safe primitive in LinuxThreads. */ @@ -827,7 +837,14 @@ GC_INNER void GC_stop_world(void) for (i = 0; i < n_live_threads; i++) { retry: - code = sem_wait(&GC_suspend_ack_sem); +# ifdef THREAD_SANITIZER + /* sem_wait() hangs sometimes. */ + while ((code = sem_trywait(&GC_suspend_ack_sem)) != 0 + && errno == EAGAIN) + usleep(100); +# else + code = sem_wait(&GC_suspend_ack_sem); +# endif if (0 != code) { /* On Linux, sem_wait is documented to always return zero. */ /* But the documentation appears to be incorrect. */