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>

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 815396d..166d59c 100644 (file)
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -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);