[PATCH 5.7 069/163] ALSA: pcm: fix snd_pcm_link() lockdep splat
From: Greg Kroah-Hartman
Date: Tue Jun 16 2020 - 12:10:14 EST
From: MichaÅ MirosÅaw <mirq-linux@xxxxxxxxxxxx>
commit e18035cf5cb3d2bf8e4f4d350a23608bd208b934 upstream.
Add and use snd_pcm_stream_lock_nested() in snd_pcm_link/unlink
implementation. The code is fine, but generates a lockdep complaint:
============================================
WARNING: possible recursive locking detected
5.7.1mq+ #381 Tainted: G O
--------------------------------------------
pulseaudio/4180 is trying to acquire lock:
ffff888402d6f508 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xda8/0xee0 [snd_pcm]
but task is already holding lock:
ffff8883f7a8cf18 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xe4e/0xee0 [snd_pcm]
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&group->lock);
lock(&group->lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
2 locks held by pulseaudio/4180:
#0: ffffffffa1a05190 (snd_pcm_link_rwsem){++++}-{3:3}, at: snd_pcm_common_ioctl+0xca0/0xee0 [snd_pcm]
#1: ffff8883f7a8cf18 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xe4e/0xee0 [snd_pcm]
[...]
Cc: stable@xxxxxxxxxxxxxxx
Fixes: f57f3df03a8e ("ALSA: pcm: More fine-grained PCM link locking")
Signed-off-by: MichaÅ MirosÅaw <mirq-linux@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/37252c65941e58473b1219ca9fab03d48f47e3e3.1591610330.git.mirq-linux@xxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
sound/core/pcm_native.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -138,6 +138,16 @@ void snd_pcm_stream_lock_irq(struct snd_
}
EXPORT_SYMBOL_GPL(snd_pcm_stream_lock_irq);
+static void snd_pcm_stream_lock_nested(struct snd_pcm_substream *substream)
+{
+ struct snd_pcm_group *group = &substream->self_group;
+
+ if (substream->pcm->nonatomic)
+ mutex_lock_nested(&group->mutex, SINGLE_DEPTH_NESTING);
+ else
+ spin_lock_nested(&group->lock, SINGLE_DEPTH_NESTING);
+}
+
/**
* snd_pcm_stream_unlock_irq - Unlock the PCM stream
* @substream: PCM substream
@@ -2200,7 +2210,7 @@ static int snd_pcm_link(struct snd_pcm_s
snd_pcm_stream_unlock_irq(substream);
snd_pcm_group_lock_irq(target_group, nonatomic);
- snd_pcm_stream_lock(substream1);
+ snd_pcm_stream_lock_nested(substream1);
snd_pcm_group_assign(substream1, target_group);
refcount_inc(&target_group->refs);
snd_pcm_stream_unlock(substream1);
@@ -2216,7 +2226,7 @@ static int snd_pcm_link(struct snd_pcm_s
static void relink_to_local(struct snd_pcm_substream *substream)
{
- snd_pcm_stream_lock(substream);
+ snd_pcm_stream_lock_nested(substream);
snd_pcm_group_assign(substream, &substream->self_group);
snd_pcm_stream_unlock(substream);
}