sound fixes for 4.5-rc5

this update contains again a few more fixes for ALSA core stuff
 although it's no longer high flux: two race fixes in sequencer and one
 PCM race fix for non-atomic PCM ops.  In addition, HD-audio gained a
 similar fix for race at reloading the driver.
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v2
 
 iQIcBAABCAAGBQJWxvBBAAoJEGwxgFQ9KSmk2RoQALqPcE1WomF9KoCTRDQ0+V2V
 CDQFBDZsrlBPNH0p5tiVOWdzk8tsKh/asF5JO83g5RmIBd3MP06MJYdMnbEa7xVE
 77WykgGT3onmiY7fka4ufNysm0LGdPNjaPvdOmzrrU0z3+JdrffuWPT2nnd6znDF
 aZH3sx/Hy+Hl7nrfhG+xh08OAQJNK9ro6ZrEzQFAdhZMUoWTAlI0cV6fTxdnMLVf
 DV9lYT4TMfCijHAu+ujPoP5TihgQ2215RvQa4GCERX2vmoXK7yPfDB6Kbkh7uQhl
 HW8blEKHKfrEOElmg/VKUKaa1W7Of+n3m1eFrBgPiDfUEzpBM4U0Bp3dr/097rnk
 v2arIBQQcu/V3yInID8BxQAH9Rq4P+wS8UREBXws5AEe0OSyMsYheVmkPOJoBSST
 uudqKSf876qqC2+ze7R90rUF91UNiWJNyraynUPPgXO5IXMpUbt6H8oucICU+vys
 eaIl/sl0n0fB3XUcMLXKGySgXxeKUGKqWPNga5v2YLdyFLhtd3uHJFuoq7vy8as2
 vzjq/sd87R2VUCxN907UKdhQkvXuhIXs5I6ugc7Wwv+RHv9dhLNs+zB8yOnA+iFT
 T6tMX0M/5lgJ+s8DH9mLUxZWb8cUjLWU0llVedBuicFAilnujIkw4Gc+3RKcf3h0
 Hj/sHiss0F9q0XhPI5gI
 =u/fj
 -----END PGP SIGNATURE-----

Merge tag 'sound-4.5-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound

Pull sound fixes from Takashi Iwai:
 "This update contains again a few more fixes for ALSA core stuff
  although it's no longer high flux: two race fixes in sequencer and one
  PCM race fix for non-atomic PCM ops.

  In addition, HD-audio gained a similar fix for race at reloading the
  driver"

* tag 'sound-4.5-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
  ALSA: pcm: Fix rwsem deadlock for non-atomic PCM stream
  ALSA: seq: Fix double port list deletion
  ALSA: hda - Cancel probe work instead of flush at remove
  ALSA: seq: Fix leak of pool buffer at concurrent writes

sound/core/pcm_native.c

@@ -74,6 +74,18 @@ static int snd_pcm_open(struct file *file, struct snd_pcm *pcm, int stream);
 static DEFINE_RWLOCK(snd_pcm_link_rwlock);
 static DECLARE_RWSEM(snd_pcm_link_rwsem);
 
+/* Writer in rwsem may block readers even during its waiting in queue,
+ * and this may lead to a deadlock when the code path takes read sem
+ * twice (e.g. one in snd_pcm_action_nonatomic() and another in
+ * snd_pcm_stream_lock()).  As a (suboptimal) workaround, let writer to
+ * spin until it gets the lock.
+ */
+static inline void down_write_nonblock(struct rw_semaphore *lock)
+{
+	while (!down_write_trylock(lock))
+		cond_resched();
+}
+
 /**
  * snd_pcm_stream_lock - Lock the PCM stream
  * @substream: PCM substream
@@ -1813,7 +1825,7 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd)
 		res = -ENOMEM;
 		goto _nolock;
 	}
-	down_write(&snd_pcm_link_rwsem);
+	down_write_nonblock(&snd_pcm_link_rwsem);
 	write_lock_irq(&snd_pcm_link_rwlock);
 	if (substream->runtime->status->state == SNDRV_PCM_STATE_OPEN ||
 	    substream->runtime->status->state != substream1->runtime->status->state ||
@@ -1860,7 +1872,7 @@ static int snd_pcm_unlink(struct snd_pcm_substream *substream)
 	struct snd_pcm_substream *s;
 	int res = 0;
 
-	down_write(&snd_pcm_link_rwsem);
+	down_write_nonblock(&snd_pcm_link_rwsem);
 	write_lock_irq(&snd_pcm_link_rwlock);
 	if (!snd_pcm_stream_linked(substream)) {
 		res = -EALREADY;

sound/core/seq/seq_memory.c

@@ -383,15 +383,20 @@ int snd_seq_pool_init(struct snd_seq_pool *pool)
 
 	if (snd_BUG_ON(!pool))
 		return -EINVAL;
-	if (pool->ptr)			/* should be atomic? */
-		return 0;
 
-	pool->ptr = vmalloc(sizeof(struct snd_seq_event_cell) * pool->size);
-	if (!pool->ptr)
+	cellptr = vmalloc(sizeof(struct snd_seq_event_cell) * pool->size);
+	if (!cellptr)
 		return -ENOMEM;
 
 	/* add new cells to the free cell list */
 	spin_lock_irqsave(&pool->lock, flags);
+	if (pool->ptr) {
+		spin_unlock_irqrestore(&pool->lock, flags);
+		vfree(cellptr);
+		return 0;
+	}
+
+	pool->ptr = cellptr;
 	pool->free = NULL;
 
 	for (cell = 0; cell < pool->size; cell++) {

sound/core/seq/seq_ports.c

@@ -535,19 +535,22 @@ static void delete_and_unsubscribe_port(struct snd_seq_client *client,
 					bool is_src, bool ack)
 {
 	struct snd_seq_port_subs_info *grp;
+	struct list_head *list;
+	bool empty;
 
 	grp = is_src ? &port->c_src : &port->c_dest;
+	list = is_src ? &subs->src_list : &subs->dest_list;
 	down_write(&grp->list_mutex);
 	write_lock_irq(&grp->list_lock);
-	if (is_src)
-		list_del(&subs->src_list);
-	else
-		list_del(&subs->dest_list);
+	empty = list_empty(list);
+	if (!empty)
+		list_del_init(list);
 	grp->exclusive = 0;
 	write_unlock_irq(&grp->list_lock);
 	up_write(&grp->list_mutex);
 
-	unsubscribe_port(client, port, grp, &subs->info, ack);
+	if (!empty)
+		unsubscribe_port(client, port, grp, &subs->info, ack);
 }
 
 /* connect two ports */

sound/pci/hda/hda_intel.c

@@ -2168,10 +2168,10 @@ static void azx_remove(struct pci_dev *pci)
 	struct hda_intel *hda;
 
 	if (card) {
-		/* flush the pending probing work */
+		/* cancel the pending probing work */
 		chip = card->private_data;
 		hda = container_of(chip, struct hda_intel, chip);
-		flush_work(&hda->probe_work);
+		cancel_work_sync(&hda->probe_work);
 
 		snd_card_free(card);
 	}