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ALSA: pcm: Fix false lockdep warnings 

As PCM core handles the multiple linked streams in parallel, lockdep
gets confused (partly because of weak annotations) and spews the
false-positive warnings.  This hasn't been a problem for long time but
the latest PCM lock path update seems to have woken up a sleeping
dog.

Here is an attempt to paper over this issue: pass the lock subclass
just calculated from the depth in snd_pcm_action_group().  Also, a
(possibly) wrong lock subclass set in snd_pcm_action_lock_mutex() is
dropped, too.

Reported-and-tested-by: Arthur Marsh <arthur.marsh@internode.on.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2014-10-21 15:32:13 +02:00
parent b1974f965a
commit dde1c652d7
1 changed files with 5 additions and 7 deletions
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12
sound/core/pcm_native.c
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@ -781,16 +781,15 @@ static int snd_pcm_action_group(struct action_ops *ops,
{
struct snd_pcm_substream *s = NULL;
struct snd_pcm_substream *s1;
int res = 0;
int res = 0, depth = 1;
snd_pcm_group_for_each_entry(s, substream) {
if (do_lock && s != substream) {
if (s->pcm->nonatomic)
mutex_lock_nested(&s->self_group.mutex,
SINGLE_DEPTH_NESTING);
mutex_lock_nested(&s->self_group.mutex, depth);
else
spin_lock_nested(&s->self_group.lock,
SINGLE_DEPTH_NESTING);
spin_lock_nested(&s->self_group.lock, depth);
depth++;
}
res = ops->pre_action(s, state);
if (res < 0)
@ -906,8 +905,7 @@ static int snd_pcm_action_lock_mutex(struct action_ops *ops,
down_read(&snd_pcm_link_rwsem);
if (snd_pcm_stream_linked(substream)) {
mutex_lock(&substream->group->mutex);
mutex_lock_nested(&substream->self_group.mutex,
SINGLE_DEPTH_NESTING);
mutex_lock(&substream->self_group.mutex);
res = snd_pcm_action_group(ops, substream, state, 1);
mutex_unlock(&substream->self_group.mutex);
mutex_unlock(&substream->group->mutex);