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authorMark Brown <broonie@opensource.wolfsonmicro.com>2009-06-03 20:43:29 +0100
committerTakashi Iwai <tiwai@suse.de>2009-06-03 23:33:28 +0200
commit872c78202c58d26596e25743791ee81a7d24abad (patch)
tree5cca75beabf74f82a26b5649e2ae9aa23e4996fb
parent10a8ebbb08c4b08292598947bbe534e04d6ee705 (diff)
downloadop-kernel-dev-872c78202c58d26596e25743791ee81a7d24abad.zip
op-kernel-dev-872c78202c58d26596e25743791ee81a7d24abad.tar.gz
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: Mark Brown <broonie@opensource.wolfsonmicro.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
-rw-r--r--sound/core/init.c31
1 files changed, 19 insertions, 12 deletions
diff --git a/sound/core/init.c b/sound/core/init.c
index 6557dd8..a578d05 100644
--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -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;
@@ -529,14 +522,16 @@ void snd_card_set_id(struct snd_card *card, const char *nid)
}
if (!snd_info_check_reserved_words(id))
goto __change;
- mutex_lock(&snd_card_mutex);
+ 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)) {
mutex_unlock(&snd_card_mutex);
goto __change;
}
}
- mutex_unlock(&snd_card_mutex);
+ if (do_locking)
+ mutex_unlock(&snd_card_mutex);
break;
__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);
#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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