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in synccall, ignore the signal before any threads' signal handlers return

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this protects against deadlock from spurious signals (e.g. sent by
another process) arriving after the controlling thread releases the
other threads from the sync operation.
This commit is contained in:
Rich Felker 2013-09-02 15:16:36 -04:00
commit 3c0501d28c
1 changed files with 4 additions and 4 deletions
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8
src/thread/synccall.c
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@ -71,6 +71,10 @@ void __synccall(void (*func)(void *), void *ctx)
sigqueue(self->pid, SIGSYNCCALL, (union sigval){0});
while (sem_wait(&chaindone));
sa.sa_flags = 0;
sa.sa_handler = SIG_IGN;
__libc_sigaction(SIGSYNCCALL, &sa, 0);
for (cur=head; cur; cur=cur->next) {
sem_post(&cur->sem);
while (sem_wait(&cur->sem2));
@ -82,10 +86,6 @@ void __synccall(void (*func)(void *), void *ctx)
sem_post(&cur->sem);
}
sa.sa_flags = 0;
sa.sa_handler = SIG_IGN;
__libc_sigaction(SIGSYNCCALL, &sa, 0);
__syscall(SYS_rt_sigprocmask, SIG_SETMASK,
&oldmask, 0, _NSIG/8);