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 c54570befc05ec95d0083d51428735e441ace6ba..90ad1e25795888851dd3acc661d4f90798203363 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);