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Date: Thu, 6 Dec 2018 02:43:11 +0000
From: Orivej Desh <orivej@....fr>
To: musl@...ts.openwall.com
Subject: Re: sem_wait and EINTR

* Rich Felker <dalias@...c.org> [2018-12-05]
> On Wed, Dec 05, 2018 at 07:16:05PM +0000, Orivej Desh wrote:
> > [3] https://github.com/orivej/musl/commit/c4c38aaab4fc55c23669f7b81386b615609cc3e1
> > 
> > diff --git a/src/thread/sem_timedwait.c b/src/thread/sem_timedwait.c
> > index 8132eb1b..58d3ebfe 100644
> > --- a/src/thread/sem_timedwait.c
> > +++ b/src/thread/sem_timedwait.c
> > @@ -22,7 +22,7 @@ int sem_timedwait(sem_t *restrict sem, const struct timespec *restrict at)
> >  		pthread_cleanup_push(cleanup, (void *)(sem->__val+1));
> >  		r = __timedwait_cp(sem->__val, -1, CLOCK_REALTIME, at, sem->__val[2]);
> >  		pthread_cleanup_pop(1);
> > -		if (r && r != EINTR) {
> > +		if (r) {
> >  			errno = r;
> >  			return -1;
> >  		}
> > diff --git a/src/thread/synccall.c b/src/thread/synccall.c
> > index cc66bd24..d9ab40cb 100644
> > --- a/src/thread/synccall.c
> > +++ b/src/thread/synccall.c
> > @@ -37,10 +37,10 @@ static void handler(int sig)
> >  	if (a_cas(&target_tid, ch.tid, 0) == (ch.tid | 0x80000000))
> >  		__syscall(SYS_futex, &target_tid, FUTEX_UNLOCK_PI|FUTEX_PRIVATE);
> >  
> > -	sem_wait(&ch.target_sem);
> > +	while (sem_wait(&ch.target_sem) && errno != EINTR);
> >  	callback(context);
> >  	sem_post(&ch.caller_sem);
> > -	sem_wait(&ch.target_sem);
> > +	while (sem_wait(&ch.target_sem) && errno != EINTR);
> >  
> >  	errno = old_errno;
> >  }
> > @@ -153,7 +153,7 @@ void __synccall(void (*func)(void *), void *ctx)
> >  	/* Serialize execution of callback in caught threads. */
> >  	for (cp=head; cp; cp=cp->next) {
> >  		sem_post(&cp->target_sem);
> > -		sem_wait(&cp->caller_sem);
> > +		while (sem_wait(&cp->caller_sem) && errno != EINTR);
> >  	}
> >  
> >  	sa.sa_handler = SIG_IGN;  
> 
> I think the changes to __synccall are unnecessary noise. It
> necessarily runs with all signals, even implementation-internal ones,
> blocked. Did you just miss this or do you think there's a reason the
> checks need to be added?

You are right, I did not notice that. There is no need to change synccall.c.

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