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Commit dde1c652 authored by Takashi Iwai's avatar Takashi Iwai
Browse files

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: default avatarArthur Marsh <arthur.marsh@internode.on.net>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent b1974f96

sound/core/pcm_native.c

+5 −7
Original line number Diff line number Diff line
@@ -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);