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BUG/MEDIUM: threads: handle signal queue only in thread 0

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Signals were handled in all threads which caused some signals to be lost
from time to time. To avoid complicated lock system (threads+signals),
we prefer handling the signals in one thread avoiding concurrent access.

The side effect of this bug was that some process were not leaving from
time to time during a reload.

This patch must be backported in 1.8.
This commit is contained in:
William Lallemand 2018-06-07 09:46:01 +02:00 committed by Willy Tarreau
parent fc044c98e4
commit 1aab50bb4a
2 changed files with 18 additions and 11 deletions
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21
src/haproxy.c
View File

@ -2402,8 +2402,10 @@ static void run_poll_loop()
/* Process a few tasks */
process_runnable_tasks();
/* check if we caught some signals and process them */
signal_process_queue();
/* check if we caught some signals and process them in the
first thread */
if (tid == 0)
signal_process_queue();
/* Check if we can expire some tasks */
next = wake_expired_tasks();
@ -2418,7 +2420,7 @@ static void run_poll_loop()
activity[tid].wake_cache++;
else if (active_tasks_mask & tid_bit)
activity[tid].wake_tasks++;
else if (signal_queue_len)
else if (signal_queue_len && tid == 0)
activity[tid].wake_signal++;
else
exp = next;
@ -3008,6 +3010,7 @@ int main(int argc, char **argv)
unsigned int *tids = calloc(global.nbthread, sizeof(unsigned int));
pthread_t *threads = calloc(global.nbthread, sizeof(pthread_t));
int i;
sigset_t blocked_sig, old_sig;
THREAD_SYNC_INIT((1UL << global.nbthread) - 1);
@ -3015,6 +3018,15 @@ int main(int argc, char **argv)
for (i = 0; i < global.nbthread; i++)
tids[i] = i;
/* ensure the signals will be blocked in every thread */
sigfillset(&blocked_sig);
sigdelset(&blocked_sig, SIGPROF);
sigdelset(&blocked_sig, SIGBUS);
sigdelset(&blocked_sig, SIGFPE);
sigdelset(&blocked_sig, SIGILL);
sigdelset(&blocked_sig, SIGSEGV);
pthread_sigmask(SIG_SETMASK, &blocked_sig, &old_sig);
/* Create nbthread-1 thread. The first thread is the current process */
threads[0] = pthread_self();
for (i = 1; i < global.nbthread; i++)
@ -3048,6 +3060,9 @@ int main(int argc, char **argv)
}
#endif /* !USE_CPU_AFFINITY */
/* when multithreading we need to let only the thread 0 handle the signals */
pthread_sigmask(SIG_SETMASK, &old_sig, NULL);
/* Finally, start the poll loop for the first thread */
run_thread_poll_loop(&tids[0]);

8
src/signal.c
View File

@ -31,7 +31,6 @@ struct pool_head *pool_head_sig_handlers = NULL;
sigset_t blocked_sig;
int signal_pending = 0; /* non-zero if t least one signal remains unprocessed */
__decl_hathreads(HA_SPINLOCK_T signals_lock);
/* Common signal handler, used by all signals. Received signals are queued.
* Signal number zero has a specific status, as it cannot be delivered by the
@ -71,9 +70,6 @@ void __signal_process_queue()
struct signal_descriptor *desc;
sigset_t old_sig;
if (HA_SPIN_TRYLOCK(SIGNALS_LOCK, &signals_lock))
return;
/* block signal delivery during processing */
sigprocmask(SIG_SETMASK, &blocked_sig, &old_sig);
@ -100,7 +96,6 @@ void __signal_process_queue()
/* restore signal delivery */
sigprocmask(SIG_SETMASK, &old_sig, NULL);
HA_SPIN_UNLOCK(SIGNALS_LOCK, &signals_lock);
}
/* perform minimal intializations, report 0 in case of error, 1 if OK. */
@ -112,8 +107,6 @@ int signal_init()
memset(signal_queue, 0, sizeof(signal_queue));
memset(signal_state, 0, sizeof(signal_state));
HA_SPIN_INIT(&signals_lock);
/* Ensure signals are not blocked. Some shells or service managers may
* accidently block all of our signals unfortunately, causing lots of
* zombie processes to remain in the background during reloads.
@ -148,7 +141,6 @@ void deinit_signals()
pool_free(pool_head_sig_handlers, sh);
}
}
HA_SPIN_DESTROY(&signals_lock);
}
/* Register a function and an integer argument on a signal. A pointer to the