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client API: avoid lost wakeups 

The commit linked below added temporary unlocking to update_prop(),
which is indirectly called by mpv_wait_event(). If an unlock happens,
and no property change event is returned, we must re-poll the event
queue. Rechecking the state on unlocks is basically a standard
requirement for code using condition variables.

Untested beyond a simple test.

Fixes: 065c307e8e
This commit is contained in:
wm4 2019-10-24 19:12:36 +02:00
parent 5d5fdb77e9
commit b0827b4dc4
1 changed files with 7 additions and 3 deletions
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10
player/client.c
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@ -139,7 +139,7 @@ struct mpv_handle {
};
static bool gen_log_message_event(struct mpv_handle *ctx);
static bool gen_property_change_event(struct mpv_handle *ctx);
static bool gen_property_change_event(struct mpv_handle *ctx, bool *unlocked);
static void notify_property_events(struct mpv_handle *ctx, uint64_t event_mask);
void mp_clients_init(struct MPContext *mpctx)
@ -834,12 +834,15 @@ mpv_event *mpv_wait_event(mpv_handle *ctx, double timeout)
talloc_steal(event, event->data);
break;
}
bool unlocked = false;
// If there's a changed property, generate change event (never queued).
if (gen_property_change_event(ctx))
if (gen_property_change_event(ctx, &unlocked))
break;
// Pop item from message queue, and return as event.
if (gen_log_message_event(ctx))
break;
if (unlocked)
continue;
int r = wait_wakeup(ctx, deadline);
if (r == ETIMEDOUT)
break;
@ -1549,7 +1552,7 @@ static bool update_prop(struct mpv_handle *ctx, struct observe_property *prop)
// Set ctx->cur_event to a generated property change event, if there is any
// outstanding property.
static bool gen_property_change_event(struct mpv_handle *ctx)
static bool gen_property_change_event(struct mpv_handle *ctx, bool *unlocked)
{
if (!ctx->mpctx->initialized)
return false;
@ -1570,6 +1573,7 @@ static bool gen_property_change_event(struct mpv_handle *ctx)
if (prop->changed && !prop->dead) {
prop->changed = false;
updated = update_prop(ctx, prop);
*unlocked = true; // not always; but good enough
}
if (prop->dead) {