Commit 872c7820 authored by Mark Brown's avatar Mark Brown Committed by Takashi Iwai
Browse files

ALSA: Fix double locking of card list in snd_card_register() 



The introduction of snd_card_set_id() added a lock on the card list
to the old choose_default_id() function when using it to implement
the new API call. This lock is needed to allow us to walk the list
and check to see if our new name is a duplicate. Unfortunately this
causes a lockup when called from snd_card_register() (in cases
where no ID is supplied for the card) since the card list is already
locked there.

Fix this fairly hideously by factoring out the implementation and
using a flag to indicate if the lock should be held. A better fix
would probably be to refactor snd_card_register() to move the
_set_id() outside the locking region but I can't immediately see
anything I can convince myself is safe.

Signed-off-by: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 10a8ebbb

sound/core/init.c

+19 −12
Original line number Diff line number Diff line
@@ -476,15 +476,8 @@ int snd_card_free(struct snd_card *card) 


EXPORT_SYMBOL(snd_card_free);



/**

 *  snd_card_set_id - set card identification name

 *  @card: soundcard structure

 *  @nid: new identification string

 *

 *  This function sets the card identification and checks for name

 *  collisions.

 */

void snd_card_set_id(struct snd_card *card, const char *nid)

static void snd_card_set_id_internal(struct snd_card *card, const char *nid,

				     int do_locking)

{

	int i, len, idx_flag = 0, loops = SNDRV_CARDS;

	const char *spos, *src;
@@ -529,6 +522,7 @@ void snd_card_set_id(struct snd_card *card, const char *nid) 
      		}

	      	if (!snd_info_check_reserved_words(id))

      			goto __change;

		if (do_locking)

			mutex_lock(&snd_card_mutex);

		for (i = 0; i < snd_ecards_limit; i++) {

			if (snd_cards[i] && !strcmp(snd_cards[i]->id, id)) {
@@ -536,6 +530,7 @@ void snd_card_set_id(struct snd_card *card, const char *nid) 
				goto __change;

			}

		}

		if (do_locking)

			mutex_unlock(&snd_card_mutex);

		break;
@@ -561,6 +556,18 @@ void snd_card_set_id(struct snd_card *card, const char *nid) 
	}

}



/**

 *  snd_card_set_id - set card identification name

 *  @card: soundcard structure

 *  @nid: new identification string

 *

 *  This function sets the card identification and checks for name

 *  collisions.

 */

void snd_card_set_id(struct snd_card *card, const char *nid)

{

	snd_card_set_id_internal(card, nid, 1);

}

EXPORT_SYMBOL(snd_card_set_id);



#ifndef CONFIG_SYSFS_DEPRECATED
@@ -657,7 +664,7 @@ int snd_card_register(struct snd_card *card) 
		return 0;

	}

	if (card->id[0] == '\0')

		snd_card_set_id(card, NULL);

		snd_card_set_id_internal(card, NULL, 0);

	snd_cards[card->number] = card;

	mutex_unlock(&snd_card_mutex);

	init_info_for_card(card);

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