From 872c78202c58d26596e25743791ee81a7d24abad Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Wed, 3 Jun 2009 20:43:29 +0100 Subject: 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 Signed-off-by: Takashi Iwai --- sound/core/init.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-) (limited to 'sound') diff --git a/sound/core/init.c b/sound/core/init.c index 6557dd85e191..a578d05f9e13 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); -- cgit v1.2.3 From 5fdc18d938c99399b73fe894bc24cb9400a1a2ee Mon Sep 17 00:00:00 2001 From: Jaroslav Kysela Date: Thu, 4 Jun 2009 00:12:18 +0200 Subject: ALSA: Core - clean up snd_card_set_id* calls and remove possible id collision Move locking outside snd_card_set_id_internal() function and rename it to snd_card_set_id_no_lock() for better function description. User defined id is just copied to card structure at allocation time. The real unique id procedure is called in snd_card_register() to ensure real atomicity. Signed-off-by: Jaroslav Kysela Signed-off-by: Takashi Iwai --- sound/core/init.c | 26 ++++++++++---------------- 1 file changed, 10 insertions(+), 16 deletions(-) (limited to 'sound') diff --git a/sound/core/init.c b/sound/core/init.c index a578d05f9e13..d5d40d78c409 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -153,7 +153,7 @@ int snd_card_create(int idx, const char *xid, if (!card) return -ENOMEM; if (xid) - snd_card_set_id(card, xid); + strlcpy(card->id, xid, sizeof(card->id)); err = 0; mutex_lock(&snd_card_mutex); if (idx < 0) { @@ -476,16 +476,12 @@ int snd_card_free(struct snd_card *card) EXPORT_SYMBOL(snd_card_free); -static void snd_card_set_id_internal(struct snd_card *card, const char *nid, - int do_locking) +static void snd_card_set_id_no_lock(struct snd_card *card, const char *nid) { int i, len, idx_flag = 0, loops = SNDRV_CARDS; const char *spos, *src; char *id; - /* check if user specified own card->id */ - if (card->id[0] != '\0') - return; if (nid == NULL) { id = card->shortname; spos = src = id; @@ -522,16 +518,10 @@ static void snd_card_set_id_internal(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)) { - mutex_unlock(&snd_card_mutex); + if (snd_cards[i] && !strcmp(snd_cards[i]->id, id)) goto __change; - } } - if (do_locking) - mutex_unlock(&snd_card_mutex); break; __change: @@ -566,7 +556,12 @@ static void snd_card_set_id_internal(struct snd_card *card, const char *nid, */ void snd_card_set_id(struct snd_card *card, const char *nid) { - snd_card_set_id_internal(card, nid, 1); + /* check if user specified own card->id */ + if (card->id[0] != '\0') + return; + mutex_lock(&snd_card_mutex); + snd_card_set_id_no_lock(card, nid); + mutex_unlock(&snd_card_mutex); } EXPORT_SYMBOL(snd_card_set_id); @@ -663,8 +658,7 @@ int snd_card_register(struct snd_card *card) mutex_unlock(&snd_card_mutex); return 0; } - if (card->id[0] == '\0') - snd_card_set_id_internal(card, NULL, 0); + snd_card_set_id_no_lock(card, card->id[0] == '\0' ? NULL : card->id); snd_cards[card->number] = card; mutex_unlock(&snd_card_mutex); init_info_for_card(card); -- cgit v1.2.3