ALSA: aloop: Replace tasklet with work

The tasklet is an old API that should be deprecated, usually can be
converted to another decent API.  In aloop driver, a tasklet is still
used for offloading the timer event task.  It can be achieved
gracefully with a work queued, too.

This patch replaces the tasklet usage in aloop driver with a simple
work.

Link: https://lore.kernel.org/r/20200903104131.21097-6-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/drivers/aloop.c

@@ -110,7 +110,7 @@ struct loopback_cable {
 	struct {
 		int stream;
 		struct snd_timer_id id;
-		struct tasklet_struct event_tasklet;
+		struct work_struct event_work;
 		struct snd_timer_instance *instance;
 	} snd_timer;
 };
@@ -309,8 +309,8 @@ static int loopback_snd_timer_close_cable(struct loopback_pcm *dpcm)
 	 */
 	snd_timer_close(cable->snd_timer.instance);
 
-	/* wait till drain tasklet has finished if requested */
-	tasklet_kill(&cable->snd_timer.event_tasklet);
+	/* wait till drain work has finished if requested */
+	cancel_work_sync(&cable->snd_timer.event_work);
 
 	snd_timer_instance_free(cable->snd_timer.instance);
 	memset(&cable->snd_timer, 0, sizeof(cable->snd_timer));
@@ -794,11 +794,11 @@ static void loopback_snd_timer_function(struct snd_timer_instance *timeri,
 					  resolution);
 }
 
-static void loopback_snd_timer_tasklet(unsigned long arg)
+static void loopback_snd_timer_work(struct work_struct *work)
 {
-	struct snd_timer_instance *timeri = (struct snd_timer_instance *)arg;
-	struct loopback_cable *cable = timeri->callback_data;
+	struct loopback_cable *cable;
 
+	cable = container_of(work, struct loopback_cable, snd_timer.event_work);
 	loopback_snd_timer_period_elapsed(cable, SNDRV_TIMER_EVENT_MSTOP, 0);
 }
 
@@ -828,9 +828,9 @@ static void loopback_snd_timer_event(struct snd_timer_instance *timeri,
 		 * state the streaming will be aborted by the usual timeout. It
 		 * should not be aborted here because may be the timer sound
 		 * card does only a recovery and the timer is back soon.
-		 * This tasklet triggers loopback_snd_timer_tasklet()
+		 * This work triggers loopback_snd_timer_work()
 		 */
-		tasklet_schedule(&cable->snd_timer.event_tasklet);
+		schedule_work(&cable->snd_timer.event_work);
 	}
 }
 
@@ -1124,7 +1124,7 @@ static int loopback_snd_timer_open(struct loopback_pcm *dpcm)
 		err = -ENOMEM;
 		goto exit;
 	}
-	/* The callback has to be called from another tasklet. If
+	/* The callback has to be called from another work. If
 	 * SNDRV_TIMER_IFLG_FAST is specified it will be called from the
 	 * snd_pcm_period_elapsed() call of the selected sound card.
 	 * snd_pcm_period_elapsed() helds snd_pcm_stream_lock_irqsave().
@@ -1137,9 +1137,8 @@ static int loopback_snd_timer_open(struct loopback_pcm *dpcm)
 	timeri->callback_data = (void *)cable;
 	timeri->ccallback = loopback_snd_timer_event;
 
-	/* initialise a tasklet used for draining */
-	tasklet_init(&cable->snd_timer.event_tasklet,
-		     loopback_snd_timer_tasklet, (unsigned long)timeri);
+	/* initialise a work used for draining */
+	INIT_WORK(&cable->snd_timer.event_work, loopback_snd_timer_work);
 
 	/* The mutex loopback->cable_lock is kept locked.
 	 * Therefore snd_timer_open() cannot be called a second time