ALSA: timer: Sync timer deletion at closing the system timer

ALSA timer core framework has no sync point at stopping because it's
called inside the spinlock.  Thus we need a sync point at close for
avoiding the stray timer task.  This is simply done by implementing
the close callback just calling del_timer_sync().  (It's harmless to
call it unconditionally, as the core timer itself cares of the already
deleted timer instance.)
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/core/timer.c

@@ -1058,11 +1058,21 @@ static int snd_timer_s_stop(struct snd_timer * timer)
 	return 0;
 }
 
+static int snd_timer_s_close(struct snd_timer *timer)
+{
+	struct snd_timer_system_private *priv;
+
+	priv = (struct snd_timer_system_private *)timer->private_data;
+	del_timer_sync(&priv->tlist);
+	return 0;
+}
+
 static struct snd_timer_hardware snd_timer_system =
 {
 	.flags =	SNDRV_TIMER_HW_FIRST | SNDRV_TIMER_HW_TASKLET,
 	.resolution =	1000000000L / HZ,
 	.ticks =	10000000L,
+	.close =	snd_timer_s_close,
 	.start =	snd_timer_s_start,
 	.stop =		snd_timer_s_stop
 };