Revert "SR-4201: DispatchSourceSignal not working on Linux"

This reverts commit d857d7f.

Author: dgrove-oss

src/event/event_epoll.c

@@ -135,7 +135,7 @@ _dispatch_muxnote_create(dispatch_unote_t du, uint32_t events)
 		if (fd < 0) {
 			return NULL;
 		}
-		pthread_sigmask(SIG_BLOCK, &sigmask, NULL);
+		sigprocmask(SIG_BLOCK, &sigmask, NULL);
 		break;
 
 	case EVFILT_WRITE:

src/queue.c

@@ -5762,25 +5762,7 @@ DISPATCH_NOINLINE DISPATCH_NORETURN
 static void
 _dispatch_sigsuspend(void)
 {
-	sigset_t mask;
-	int r;
-
-	r = sigemptyset(&mask);
-	(void)dispatch_assume_zero(r);
-
-#if DISPATCH_EVENT_BACKEND_EPOLL
-	// If there are signals that the user may have reasonably
-	// created a DispatchSignalSource to monitor and might
-	// reasonably be sent to the main thread after it has called
-	// dispatch_main, we have to include them in the sigsuspend mask
-	// or they won't be properly delivered to the signalfd.
-	r = sigaddset(&mask, SIGUSR1);
-	(void)dispatch_assume_zero(r);
-	r = sigaddset(&mask, SIGUSR2);
-	(void)dispatch_assume_zero(r);
-	r = sigaddset(&mask, SIGCHLD);
-	(void)dispatch_assume_zero(r);
-#endif
+	static const sigset_t mask;
 
 	for (;;) {
 		sigsuspend(&mask);