3.19.8-ckt6 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Takashi Iwai <tiwai@xxxxxxx>
commit 67756e3191c90e7c0b94b8b2fb63de255b6cd337 upstream.
With the nonatomic PCM ops, the system may spew lockdep warnings like:
=============================================
[ INFO: possible recursive locking detected ]
4.2.0-rc1-jeejaval3 #12 Not tainted
---------------------------------------------
aplay/4029 is trying to acquire lock:
(snd_pcm_link_rwsem){.+.+.+}, at: [<ffffffff816fd473>] snd_pcm_stream_lock+0x43/0x60
but task is already holding lock:
(snd_pcm_link_rwsem){.+.+.+}, at: [<ffffffff816fcf29>] snd_pcm_action_nonatomic+0x29/0x80
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(snd_pcm_link_rwsem);
lock(snd_pcm_link_rwsem);
Although this is false-positive as the rwsem is taken always as
read-only for these code paths, it's certainly annoying to see this at
any occasion. A simple fix is to use down_read_nested() in
snd_pcm_stream_lock() that can be called inside another lock.
Reported-by: Vinod Koul <vinod.koul@xxxxxxxxx>
Reported-by: Jeeja Kp <jeeja.kp@xxxxxxxxx>
Tested-by: Jeeja Kp <jeeja.kp@xxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
sound/core/pcm_native.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 64d9863..3f2ac8d 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -85,7 +85,7 @@ static DECLARE_RWSEM(snd_pcm_link_rwsem);
void snd_pcm_stream_lock(struct snd_pcm_substream *substream)
{
if (substream->pcm->nonatomic) {
- down_read(&snd_pcm_link_rwsem);
+ down_read_nested(&snd_pcm_link_rwsem, SINGLE_DEPTH_NESTING);
mutex_lock(&substream->self_group.mutex);
} else {
read_lock(&snd_pcm_link_rwlock);
--
1.9.1
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