ALSA: hda - Use own workqueue

snd-hda-intel driver used schedule_work() fot the delayed DMA pointer
updates, but this has several potential problems:
- it may block other eventsd works longer
- it may deadlock when probing fails and flush_scheduled_work() is
  called during probe callback (as probe callback itself could be
  invoked from eventd)

This patch adds an own workq for each driver instance to solve these
problems.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_beep.c

@@ -135,7 +135,6 @@ void snd_hda_detach_beep_device(struct hda_codec *codec)
 	struct hda_beep *beep = codec->beep;
 	if (beep) {
 		cancel_work_sync(&beep->beep_work);
-		flush_scheduled_work();
 
 		input_unregister_device(beep->dev);
 		kfree(beep);

sound/pci/hda/hda_codec.c

@@ -373,7 +373,7 @@ int snd_hda_queue_unsol_event(struct hda_bus *bus, u32 res, u32 res_ex)
 	unsol->queue[wp] = res;
 	unsol->queue[wp + 1] = res_ex;
 
-	schedule_work(&unsol->work);
+	queue_work(bus->workq, &unsol->work);
 
 	return 0;
 }
@@ -437,15 +437,17 @@ static int snd_hda_bus_free(struct hda_bus *bus)
 
 	if (!bus)
 		return 0;
-	if (bus->unsol) {
-		flush_scheduled_work();
+	if (bus->workq)
+		flush_workqueue(bus->workq);
+	if (bus->unsol)
 		kfree(bus->unsol);
-	}
 	list_for_each_entry_safe(codec, n, &bus->codec_list, list) {
 		snd_hda_codec_free(codec);
 	}
 	if (bus->ops.private_free)
 		bus->ops.private_free(bus);
+	if (bus->workq)
+		destroy_workqueue(bus->workq);
 	kfree(bus);
 	return 0;
 }
@@ -485,6 +487,7 @@ int /*__devinit*/ snd_hda_bus_new(struct snd_card *card,
 {
 	struct hda_bus *bus;
 	int err;
+	char qname[8];
 	static struct snd_device_ops dev_ops = {
 		.dev_register = snd_hda_bus_dev_register,
 		.dev_free = snd_hda_bus_dev_free,
@@ -514,6 +517,14 @@ int /*__devinit*/ snd_hda_bus_new(struct snd_card *card,
 	mutex_init(&bus->cmd_mutex);
 	INIT_LIST_HEAD(&bus->codec_list);
 
+	snprintf(qname, sizeof(qname), "hda%d", card->number);
+	bus->workq = create_workqueue(qname);
+	if (!bus->workq) {
+		snd_printk(KERN_ERR "cannot create workqueue %s\n", qname);
+		kfree(bus);
+		return -ENOMEM;
+	}
+
 	err = snd_device_new(card, SNDRV_DEV_BUS, bus, &dev_ops);
 	if (err < 0) {
 		snd_hda_bus_free(bus);
@@ -684,7 +695,7 @@ static void snd_hda_codec_free(struct hda_codec *codec)
 		return;
 #ifdef CONFIG_SND_HDA_POWER_SAVE
 	cancel_delayed_work(&codec->power_work);
-	flush_scheduled_work();
+	flush_workqueue(codec->bus->workq);
 #endif
 	list_del(&codec->list);
 	snd_array_free(&codec->mixers);
@@ -1273,7 +1284,7 @@ void snd_hda_codec_reset(struct hda_codec *codec)
 
 #ifdef CONFIG_SND_HDA_POWER_SAVE
 	cancel_delayed_work(&codec->power_work);
-	flush_scheduled_work();
+	flush_workqueue(codec->bus->workq);
 #endif
 	snd_hda_ctls_clear(codec);
 	/* relase PCMs */

sound/pci/hda/hda_codec.h

@@ -614,6 +614,7 @@ struct hda_bus {
 
 	/* unsolicited event queue */
 	struct hda_bus_unsolicited *unsol;
+	struct workqueue_struct *workq;	/* common workqueue for codecs */
 
 	/* assigned PCMs */
 	DECLARE_BITMAP(pcm_dev_bits, SNDRV_PCM_DEVICES);

sound/pci/hda/hda_intel.c

@@ -996,10 +996,11 @@ static irqreturn_t azx_interrupt(int irq, void *dev_id)
 				spin_unlock(&chip->reg_lock);
 				snd_pcm_period_elapsed(azx_dev->substream);
 				spin_lock(&chip->reg_lock);
-			} else {
+			} else if (chip->bus && chip->bus->workq) {
 				/* bogus IRQ, process it later */
 				azx_dev->irq_pending = 1;
-				schedule_work(&chip->irq_pending_work);
+				queue_work(chip->bus->workq,
+					   &chip->irq_pending_work);
 			}
 		}
 	}
@@ -1741,7 +1742,6 @@ static void azx_clear_irq_pending(struct azx *chip)
 	for (i = 0; i < chip->num_streams; i++)
 		chip->azx_dev[i].irq_pending = 0;
 	spin_unlock_irq(&chip->reg_lock);
-	flush_scheduled_work();
 }
 
 static struct snd_pcm_ops azx_pcm_ops = {