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authorTakashi Iwai <tiwai@suse.de>2020-09-22 11:49:53 +0300
committerTakashi Iwai <tiwai@suse.de>2020-09-22 12:07:10 +0300
commit6564d0ad67efb2d977e130e7448505ee538af016 (patch)
tree7c8bc723dd5c3924053ad21f505f333b00f32a59 /sound/core
parent534ad9afb19b5ac810a5e1c638f371e81e0c1ed6 (diff)
downloadlinux-6564d0ad67efb2d977e130e7448505ee538af016.tar.xz
ALSA: ctl: Workaround for lockdep warning wrt card->ctl_files_rwlock
The recent change in lockdep for read lock caused the deadlock warnings in ALSA control code which uses the read_lock() for notification and else while write_lock_irqsave() is used for adding and removing the list entry. Although a deadlock would practically never hit in a real usage (the addition and the deletion can't happen with the notification), it's better to fix the read_lock() usage in a semantically correct way. This patch replaces the read_lock() calls with read_lock_irqsave() version for avoiding a reported deadlock. The notification code path takes the irq disablement in anyway, and other code paths are very short execution, hence there shouldn't be any big performance hit by this change. Fixes: e918188611f0 ("locking: More accurate annotations for read_lock()") Reported-by: syzbot+561a74f84100162990b2@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/20200922084953.29018-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core')
-rw-r--r--sound/core/control.c18
1 files changed, 10 insertions, 8 deletions
diff --git a/sound/core/control.c b/sound/core/control.c
index e014598142df..421ddc76f264 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -150,14 +150,14 @@ void snd_ctl_notify(struct snd_card *card, unsigned int mask,
return;
if (card->shutdown)
return;
- read_lock(&card->ctl_files_rwlock);
+ read_lock_irqsave(&card->ctl_files_rwlock, flags);
#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
card->mixer_oss_change_count++;
#endif
list_for_each_entry(ctl, &card->ctl_files, list) {
if (!ctl->subscribed)
continue;
- spin_lock_irqsave(&ctl->read_lock, flags);
+ spin_lock(&ctl->read_lock);
list_for_each_entry(ev, &ctl->events, list) {
if (ev->id.numid == id->numid) {
ev->mask |= mask;
@@ -174,10 +174,10 @@ void snd_ctl_notify(struct snd_card *card, unsigned int mask,
}
_found:
wake_up(&ctl->change_sleep);
- spin_unlock_irqrestore(&ctl->read_lock, flags);
+ spin_unlock(&ctl->read_lock);
kill_fasync(&ctl->fasync, SIGIO, POLL_IN);
}
- read_unlock(&card->ctl_files_rwlock);
+ read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
}
EXPORT_SYMBOL(snd_ctl_notify);
@@ -1951,8 +1951,9 @@ int snd_ctl_get_preferred_subdevice(struct snd_card *card, int type)
{
struct snd_ctl_file *kctl;
int subdevice = -1;
+ unsigned long flags;
- read_lock(&card->ctl_files_rwlock);
+ read_lock_irqsave(&card->ctl_files_rwlock, flags);
list_for_each_entry(kctl, &card->ctl_files, list) {
if (kctl->pid == task_pid(current)) {
subdevice = kctl->preferred_subdevice[type];
@@ -1960,7 +1961,7 @@ int snd_ctl_get_preferred_subdevice(struct snd_card *card, int type)
break;
}
}
- read_unlock(&card->ctl_files_rwlock);
+ read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
return subdevice;
}
EXPORT_SYMBOL_GPL(snd_ctl_get_preferred_subdevice);
@@ -2009,13 +2010,14 @@ static int snd_ctl_dev_disconnect(struct snd_device *device)
{
struct snd_card *card = device->device_data;
struct snd_ctl_file *ctl;
+ unsigned long flags;
- read_lock(&card->ctl_files_rwlock);
+ read_lock_irqsave(&card->ctl_files_rwlock, flags);
list_for_each_entry(ctl, &card->ctl_files, list) {
wake_up(&ctl->change_sleep);
kill_fasync(&ctl->fasync, SIGIO, POLL_ERR);
}
- read_unlock(&card->ctl_files_rwlock);
+ read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
return snd_unregister_device(&card->ctl_dev);
}