2 files changed, 8 insertions, 4 deletions
diff --git a/src/bus.c b/src/bus.c
index 0c121a6..614f7ad 100644
--- a/src/bus.c
+++ b/src/bus.c
@@ -723,7 +723,7 @@ const char *
 bus_poll(bus_t *bus, int flags)
 {
 	int state = 0, saved_errno;
-	(void) flags; /* TODO nonblocking */
+	(void) flags;
 	if (!bus->first_poll) {
 		t(release_semaphore(bus, W, SEM_UNDO));  state++;
 		t(acquire_semaphore(bus, S, SEM_UNDO));  state++;
@@ -734,8 +734,9 @@ bus_poll(bus_t *bus, int flags)
 	} else {
 		bus->first_poll = 0;
 	}
+	state--;
 	t(release_semaphore(bus, Q, 0));
-	t(zero_semaphore(bus, Q, 0));
+	t(zero_semaphore(bus, Q, F(BUS_NOWAIT, IPC_NOWAIT)));
 	return bus->message;
 
 fail:
@@ -744,6 +745,8 @@ fail:
 		release_semaphore(bus, S, SEM_UNDO);
 	if (state > 0)
 		acquire_semaphore(bus, W, SEM_UNDO);
+	if (state < 0)
+		bus->first_poll = 1;
 	errno = saved_errno;
 	return NULL;
 }
diff --git a/src/bus.h b/src/bus.h
index ed1c5de..ac03106 100644
--- a/src/bus.h
+++ b/src/bus.h
@@ -101,7 +101,8 @@ typedef struct bus
 
 	/**
 	 * Non-zero if and only if `bus_poll` has not been
-	 * called since the last `bus_poll_start`
+	 * called since the last `bus_poll_start`, or
+	 * if `bus_poll` failed during reading
 	 */
 	int first_poll;
 } bus_t;
@@ -190,7 +191,7 @@ int bus_read(const bus_t *bus, int (*callback)(const char *message, void *user_d
 
 int bus_poll_start(bus_t *bus);
 int bus_poll_stop(const bus_t *bus);
-const char *bus_poll(bus_t *bus, int falgs);
+const char *bus_poll(bus_t *bus, int flags);