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

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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: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Mark Brown 2009-06-03 20:43:29 +01:00 committed by Takashi Iwai
parent 10a8ebbb08
commit 872c78202c
1 changed files with 19 additions and 12 deletions
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31
sound/core/init.c
View file

@ -476,15 +476,8 @@ int snd_card_free(struct snd_card *card)
EXPORT_SYMBOL(snd_card_free); EXPORT_SYMBOL(snd_card_free);
/** static void snd_card_set_id_internal(struct snd_card *card, const char *nid,
* snd_card_set_id - set card identification name int do_locking)
* @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)
{ {
int i, len, idx_flag = 0, loops = SNDRV_CARDS; int i, len, idx_flag = 0, loops = SNDRV_CARDS;
const char *spos, *src; const char *spos, *src;
@ -529,14 +522,16 @@ void snd_card_set_id(struct snd_card *card, const char *nid)
} }
if (!snd_info_check_reserved_words(id)) if (!snd_info_check_reserved_words(id))
goto __change; goto __change;
mutex_lock(&snd_card_mutex); if (do_locking)
mutex_lock(&snd_card_mutex);
for (i = 0; i < snd_ecards_limit; i++) { for (i = 0; i < snd_ecards_limit; i++) {
if (snd_cards[i] && !strcmp(snd_cards[i]->id, id)) { if (snd_cards[i] && !strcmp(snd_cards[i]->id, id)) {
mutex_unlock(&snd_card_mutex); mutex_unlock(&snd_card_mutex);
goto __change; goto __change;
} }
} }
mutex_unlock(&snd_card_mutex); if (do_locking)
mutex_unlock(&snd_card_mutex);
break; break;
__change: __change:
@ -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); EXPORT_SYMBOL(snd_card_set_id);
#ifndef CONFIG_SYSFS_DEPRECATED #ifndef CONFIG_SYSFS_DEPRECATED
@ -657,7 +664,7 @@ int snd_card_register(struct snd_card *card)
return 0; return 0;
} }
if (card->id[0] == '\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; snd_cards[card->number] = card;
mutex_unlock(&snd_card_mutex); mutex_unlock(&snd_card_mutex);
init_info_for_card(card); init_info_for_card(card);