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

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.

diff --git a/src/thread/synccall.c b/src/thread/synccall.c
index c54570b..90ad1e2 100644 (file)
--- a/src/thread/synccall.c
+++ b/src/thread/synccall.c
@@ -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);