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Handle pthread restart signals loss if retry_signals

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Issue #181 (bdwgc).

* doc/README.environment (GC_RETRY_SIGNALS, GC_NO_RETRY_SIGNALS):
Update documentation (support of restart signals loss, try signals
if compiled with ASan/MSan/TSan).
* pthread_stop_world.c [!GC_OPENBSD_UTHREADS && !NACL]
(GC_retry_signals): Set true also if ADDRESS_SANITIZER or
MEMORY_SANITIZER.
* pthread_stop_world.c [!GC_OPENBSD_UTHREADS && !NACL
&& !GC_NETBSD_THREADS_WORKAROUND] (GC_suspend_handler_inner): Call
sem_post(GC_suspend_ack_sem) at the function end if GC_retry_signals;
update comment about the RESTART signal loss.
* pthread_stop_world.c [!GC_OPENBSD_UTHREADS && !NACL
&& !GC_OPENBSD_UTHREADS] (GC_start_world): Call
resend_lost_signals(GC_restart_all) and update n_live_threads value.
* pthread_stop_world.c [!GC_OPENBSD_UTHREADS && !NACL
&& !GC_OPENBSD_UTHREADS && !GC_NETBSD_THREADS_WORKAROUND]
(GC_start_world): Call suspend_restart_barrier() if GC_retry_signals.
* pthread_stop_world.c [!GC_OPENBSD_UTHREADS && !NACL] (GC_stop_init):
Update the message logged if GC_retry_signals.
This commit is contained in:
Ivan Maidanski
2018-04-03 01:23:01 +03:00
parent 09c682780e
commit 3498427481
2 changed files with 24 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files
doc/README.environment
+3 -5
View File
@@ -97,11 +97,9 @@ GC_PRINT_BACK_HEIGHT - Print max length of chain through unreachable objects
(http://www.hpl.hp.com/techreports/2001/HPL-2001-251.html).
GC_RETRY_SIGNALS, GC_NO_RETRY_SIGNALS - Try to compensate for lost
thread suspend signals (Pthreads only). On by
default for OSF1, off otherwise. Note
that this does not work around a possible loss of
thread restart signals. This seems to be necessary for
some versions of Tru64. Since we've previously seen
thread suspend and restart signals (Pthreads only).
On by default for OSF1 (Tru64) or if the library is
sanitized, off otherwise. Since we've previously seen
similar issues on some other operating systems, it
was turned into a runtime flag to enable last-minute
work-arounds.
pthread_stop_world.c
+21 -10
View File
@@ -123,7 +123,8 @@ STATIC volatile AO_t GC_world_is_stopped = FALSE;
/* before they are expected to stop (unless */
/* they have stopped voluntarily). */
#if defined(GC_OSF1_THREADS) || defined(THREAD_SANITIZER)
#if defined(GC_OSF1_THREADS) || defined(THREAD_SANITIZER) \
|| defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER)
STATIC GC_bool GC_retry_signals = TRUE;
#else
STATIC GC_bool GC_retry_signals = FALSE;
@@ -362,18 +363,20 @@ STATIC void GC_suspend_handler_inner(ptr_t dummy GC_ATTR_UNUSED,
sigsuspend (&suspend_handler_mask);
} while (AO_load_acquire(&GC_world_is_stopped)
&& AO_load(&GC_stop_count) == my_stop_count);
/* If the RESTART signal gets lost, we can still lose. That should */
/* be less likely than losing the SUSPEND signal, since we don't do */
/* much between the sem_post and sigsuspend. */
/* We'd need more handshaking to work around that. */
/* Simply dropping the sigsuspend call should be safe, but is */
/* unlikely to be efficient. */
# ifdef DEBUG_THREADS
GC_log_printf("Continuing %p\n", (void *)self);
# endif
# ifdef GC_NETBSD_THREADS_WORKAROUND
sem_post(&GC_suspend_ack_sem);
# else
if (GC_retry_signals) {
/* If the RESTART signal loss is possible (though it should be */
/* less likely than losing the SUSPEND signal as we do not do */
/* much between the sem_post and sigsuspend calls), more */
/* handshaking is provided to work around it. */
sem_post(&GC_suspend_ack_sem);
}
# endif
RESTORE_CANCEL(cancel_state);
}
@@ -1107,8 +1110,15 @@ GC_INNER void GC_start_world(void)
/* the list of functions which synchronize memory). */
# endif
n_live_threads = GC_restart_all();
# if !defined(GC_OPENBSD_UTHREADS) && defined(GC_NETBSD_THREADS_WORKAROUND)
suspend_restart_barrier(n_live_threads);
# ifndef GC_OPENBSD_UTHREADS
if (GC_retry_signals)
n_live_threads = resend_lost_signals(n_live_threads, GC_restart_all);
# ifdef GC_NETBSD_THREADS_WORKAROUND
suspend_restart_barrier(n_live_threads);
# else
if (GC_retry_signals)
suspend_restart_barrier(n_live_threads);
# endif
# else
(void)n_live_threads;
# endif
@@ -1193,7 +1203,8 @@ GC_INNER void GC_stop_init(void)
GC_retry_signals = FALSE;
}
if (GC_retry_signals) {
GC_COND_LOG_PRINTF("Will retry suspend signal if necessary\n");
GC_COND_LOG_PRINTF(
"Will retry suspend and restart signals if necessary\n");
}
# ifndef NO_SIGNALS_UNBLOCK_IN_MAIN
/* Explicitly unblock the signals once before new threads creation. */