2 files changed, 17 insertions, 16 deletions

diff --git a/src/bus.c b/src/bus.c
index b17d897..c69c492 100644
--- a/src/bus.c
+++ b/src/bus.c
@@ -415,6 +415,7 @@ bus_create(const char *file, int flags, char **out_file)
 	bus.key_sem = -1;
 	bus.key_shm = -1;
 	bus.message = NULL;
+	bus.first_poll = 0;
 
 	srand((unsigned int)time(NULL) + (unsigned int)rand());
 
@@ -667,8 +668,9 @@ fail:
 
 
 int
-bus_poll_start(const bus_t *bus)
+bus_poll_start(bus_t *bus)
 {
+	bus->first_poll = 1;
 	return release_semaphore(bus, S, SEM_UNDO);
 }
 
@@ -680,23 +682,17 @@ bus_poll_stop(const bus_t *bus)
 }
 
 
-int
-bus_poll_continue(const bus_t *bus)
-{
-	t(release_semaphore(bus, W, SEM_UNDO));
-	t(acquire_semaphore(bus, S, SEM_UNDO));
-	t(zero_semaphore(bus, S));
-	t(release_semaphore(bus, S, SEM_UNDO));
-	t(acquire_semaphore(bus, W, SEM_UNDO));
-	return 0;
-fail:
-	return -1;
-}
-
-
 const char *
 bus_poll(const bus_t *bus)
 {
+	if (bus->first_poll) {
+		bus->first_poll = 0;
+		t(release_semaphore(bus, W, SEM_UNDO));
+		t(acquire_semaphore(bus, S, SEM_UNDO));
+		t(zero_semaphore(bus, S));
+		t(release_semaphore(bus, S, SEM_UNDO));
+		t(acquire_semaphore(bus, W, SEM_UNDO));
+	}
 	t(release_semaphore(bus, Q, 0));
 	t(zero_semaphore(bus, Q));
 	return bus->message;
diff --git a/src/bus.h b/src/bus.h
index 64acba7..d30a5d9 100644
--- a/src/bus.h
+++ b/src/bus.h
@@ -92,6 +92,12 @@ typedef struct bus
 	 * The address of the shared memory
 	 */
 	char *message;
+
+	/**
+	 * Non-zero if and only if `bus_poll` has not been
+	 * called since the last `bus_poll_start`
+	 */
+	int first_poll;
 } bus_t;
 
 
@@ -175,7 +181,6 @@ int bus_read(const bus_t *bus, int (*callback)(const char *message, void *user_d
 
 int bus_poll_start(const bus_t *bus);
 int bus_poll_stop(const bus_t *bus);
-int bus_poll_continue(const bus_t *bus);
 const char *bus_poll(const bus_t *bus);