poll: rework timeout

kernel-src/io/net/arp.c

@@ -270,7 +270,7 @@ int arp_lookup(netdev_t *netdev, uint32_t ip, mac_t *mac) {
 		}
 
 		MUTEX_RELEASE(&cachelock);
-		int timedout = EVENT_WAIT(&eventlistener, to);
+		e = EVENT_WAIT(&eventlistener, to);
 		MUTEX_ACQUIRE(&cachelock);
 		time = timekeeper_time();
 
@@ -279,7 +279,10 @@ int arp_lookup(netdev_t *netdev, uint32_t ip, mac_t *mac) {
 			break;
 		}
 
-		if (timedout || time.s > end.s || (end.s == time.s && time.ns >= end.ns)) {
+		if (e == EINTR)
+			return e;
+
+		if (e == ETIMEDOUT || time.s > end.s || (end.s == time.s && time.ns >= end.ns)) {
 			e = ENETUNREACH;
 			break;
 		}

kernel-src/io/poll.c

@@ -79,7 +79,7 @@ static void timeout(context_t *, dpcarg_t arg) {
 	spinlock_acquire(&desc->eventlock);
 
 	if (spinlock_try(&desc->lock))
-		sched_wakeup(desc->thread, 1);
+		sched_wakeup(desc->thread, ETIMEDOUT);
 
 	spinlock_release(&desc->eventlock);
 	interrupt_set(intstate);
@@ -115,15 +115,13 @@ int poll_dowait(polldesc_t *desc, size_t ustimeout) {
 		ret = EINTR;
 	}
 
-	if (ustimeout != 0 && ret != 1) {
+	if (ustimeout != 0 && ret != ETIMEDOUT) {
 		timer_remove(current_cpu()->timer, &sleepentry);
 		sched_target_cpu(NULL);
 	}
 
 	interrupt_set(intstate);
 
-	ret = ret == 1 ? 0 : ret;
-
 	return ret;
 }
 

kernel-src/io/tty.c

@@ -266,17 +266,16 @@ static int read(int minor, iovec_iterator_t *iovec_iterator, size_t size, uintma
 
 		error = poll_dowait(&desc, effectivetimeout);
 
-
-		if (error == 0 && (desc.event == NULL || (desc.event && desc.event->revents == 0))) {
-			// timed out!
-			poll_leave(&desc);
-			poll_destroydesc(&desc);
-			break;
-		}
-
 		poll_leave(&desc);
 		poll_destroydesc(&desc);
 
+		if (error == ETIMEDOUT) {
+			// this does not return an error on timeout.
+			// instead, it just returns the number of bytes read.
+			error = 0;
+			break;
+		}
+
 		if (error)
 			goto leave;
 	}