diff options
authorwm4 <wm4@nowhere>2020-02-13 01:06:02 +0100
committerwm4 <wm4@nowhere>2020-02-13 01:28:14 +0100
commitf3c498c7f10dea395ee098a4d1d7e2f9602e2a99 (patch)
parent7e6ea02183293dce4862f795d7e3d1080570f9c2 (diff)
ao: avoid unnecessary wakeups
If ao_add_events() is used, but all events flags are already set, then we don't need to wakeup the core again. Also, make the underrun message "exact" by avoiding the race condition mentioned in the comment. Avoiding redundant wakeups is not really worth the trouble, and it's actually just a bonus in the change making the ao_underrun_event() function return whether a new underrun was set, which is needed by the following commit.
3 files changed, 14 insertions, 9 deletions
diff --git a/audio/out/ao.c b/audio/out/ao.c
index 73131020c0..fa6cc9e76d 100644
--- a/audio/out/ao.c
+++ b/audio/out/ao.c
@@ -444,10 +444,14 @@ int ao_query_and_reset_events(struct ao *ao, int events)
return atomic_fetch_and(&ao->events_, ~(unsigned)events) & events;
-void ao_add_events(struct ao *ao, int events)
+// Returns events that were set by this calls.
+int ao_add_events(struct ao *ao, int events)
- atomic_fetch_or(&ao->events_, events);
- ao->wakeup_cb(ao->wakeup_ctx);
+ unsigned prev_events = atomic_fetch_or(&ao->events_, events);
+ unsigned new = events & ~prev_events;
+ if (new)
+ ao->wakeup_cb(ao->wakeup_ctx);
+ return new;
// Request that the player core destroys and recreates the AO. Fully thread-safe.
@@ -462,12 +466,13 @@ void ao_hotplug_event(struct ao *ao)
ao_add_events(ao, AO_EVENT_HOTPLUG);
-void ao_underrun_event(struct ao *ao)
+// Returns whether this call actually set a new underrun flag.
+bool ao_underrun_event(struct ao *ao)
- // Racy check, but it's just for the message.
- if (!(atomic_load(&ao->events_) & AO_EVENT_UNDERRUN))
+ bool new_underrun = ao_add_events(ao, AO_EVENT_UNDERRUN);
+ if (new_underrun)
MP_WARN(ao, "Device underrun detected.\n");
- ao_add_events(ao, AO_EVENT_UNDERRUN);
+ return new_underrun;
bool ao_chmap_sel_adjust(struct ao *ao, const struct mp_chmap_sel *s,
diff --git a/audio/out/ao.h b/audio/out/ao.h
index f6b984ff30..eb9e29dacb 100644
--- a/audio/out/ao.h
+++ b/audio/out/ao.h
@@ -110,7 +110,7 @@ void ao_resume(struct ao *ao);
void ao_drain(struct ao *ao);
bool ao_eof_reached(struct ao *ao);
int ao_query_and_reset_events(struct ao *ao, int events);
-void ao_add_events(struct ao *ao, int events);
+int ao_add_events(struct ao *ao, int events);
void ao_unblock(struct ao *ao);
void ao_request_reload(struct ao *ao);
void ao_hotplug_event(struct ao *ao);
diff --git a/audio/out/internal.h b/audio/out/internal.h
index d1d7482ec1..7d1d744991 100644
--- a/audio/out/internal.h
+++ b/audio/out/internal.h
@@ -211,7 +211,7 @@ struct pollfd;
int ao_wait_poll(struct ao *ao, struct pollfd *fds, int num_fds,
pthread_mutex_t *lock);
void ao_wakeup_poll(struct ao *ao);
-void ao_underrun_event(struct ao *ao);
+bool ao_underrun_event(struct ao *ao);
bool ao_chmap_sel_adjust(struct ao *ao, const struct mp_chmap_sel *s,
struct mp_chmap *map);