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| author | Takashi Iwai <tiwai@suse.de> | 2012-10-16 13:05:59 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2012-10-30 11:07:10 +0100 |
| commit | a0830dbd4e42b38aefdf3fb61ba5019a1a99ea85 (patch) | |
| tree | 4dc74b708a07b56d12ed72a34d0a2e0cb8c8b9d4 /sound/core/init.c | |
| parent | 888ea7d5ac6815ba16b3b3a20f665a92c7af6724 (diff) | |
| download | linux-a0830dbd4e42b38aefdf3fb61ba5019a1a99ea85.tar.gz | |
ALSA: Add a reference counter to card instance
For more strict protection for wild disconnections, a refcount is introduced to the card instance, and let it up/down when an object is referred via snd_lookup_*() in the open ops. The free-after-last-close check is also changed to check this refcount instead of the empty list, too. Reported-by: Matthieu CASTET <matthieu.castet@parrot.com> Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core/init.c')
| -rw-r--r-- | sound/core/init.c | 50 |
1 files changed, 30 insertions, 20 deletions
diff --git a/sound/core/init.c b/sound/core/init.c index d8ec849af128..7b012d15c2cf 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -213,6 +213,7 @@ int snd_card_create(int idx, const char *xid, spin_lock_init(&card->files_lock); INIT_LIST_HEAD(&card->files_list); init_waitqueue_head(&card->shutdown_sleep); + atomic_set(&card->refcount, 0); #ifdef CONFIG_PM mutex_init(&card->power_lock); init_waitqueue_head(&card->power_sleep); @@ -446,21 +447,36 @@ static int snd_card_do_free(struct snd_card *card) return 0; } +/** + * snd_card_unref - release the reference counter + * @card: the card instance + * + * Decrements the reference counter. When it reaches to zero, wake up + * the sleeper and call the destructor if needed. + */ +void snd_card_unref(struct snd_card *card) +{ + if (atomic_dec_and_test(&card->refcount)) { + wake_up(&card->shutdown_sleep); + if (card->free_on_last_close) + snd_card_do_free(card); + } +} +EXPORT_SYMBOL(snd_card_unref); + int snd_card_free_when_closed(struct snd_card *card) { - int free_now = 0; - int ret = snd_card_disconnect(card); - if (ret) - return ret; + int ret; - spin_lock(&card->files_lock); - if (list_empty(&card->files_list)) - free_now = 1; - else - card->free_on_last_close = 1; - spin_unlock(&card->files_lock); + atomic_inc(&card->refcount); + ret = snd_card_disconnect(card); + if (ret) { + atomic_dec(&card->refcount); + return ret; + } - if (free_now) + card->free_on_last_close = 1; + if (atomic_dec_and_test(&card->refcount)) snd_card_do_free(card); return 0; } @@ -474,7 +490,7 @@ int snd_card_free(struct snd_card *card) return ret; /* wait, until all devices are ready for the free operation */ - wait_event(card->shutdown_sleep, list_empty(&card->files_list)); + wait_event(card->shutdown_sleep, !atomic_read(&card->refcount)); snd_card_do_free(card); return 0; } @@ -886,6 +902,7 @@ int snd_card_file_add(struct snd_card *card, struct file *file) return -ENODEV; } list_add(&mfile->list, &card->files_list); + atomic_inc(&card->refcount); spin_unlock(&card->files_lock); return 0; } @@ -908,7 +925,6 @@ EXPORT_SYMBOL(snd_card_file_add); int snd_card_file_remove(struct snd_card *card, struct file *file) { struct snd_monitor_file *mfile, *found = NULL; - int last_close = 0; spin_lock(&card->files_lock); list_for_each_entry(mfile, &card->files_list, list) { @@ -923,19 +939,13 @@ int snd_card_file_remove(struct snd_card *card, struct file *file) break; } } - if (list_empty(&card->files_list)) - last_close = 1; spin_unlock(&card->files_lock); - if (last_close) { - wake_up(&card->shutdown_sleep); - if (card->free_on_last_close) - snd_card_do_free(card); - } if (!found) { snd_printk(KERN_ERR "ALSA card file remove problem (%p)\n", file); return -ENOENT; } kfree(found); + snd_card_unref(card); return 0; } |