Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1214962 > unrolled thread

[PATCH 3.19.y-ckt 018/130] ALSA: pcm: Fix lockdep warning with nonatomic PCM ops

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  [PATCH 3.19.y-ckt 018/130] ALSA: pcm: Fix lockdep warning with nonatomic PCM ops Kamal Mostafa <kamal@canonical.com> - 2015-08-28 00:50 +0200

#1214962 — [PATCH 3.19.y-ckt 018/130] ALSA: pcm: Fix lockdep warning with nonatomic PCM ops

3.19.8-ckt6 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@suse.de>

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@intel.com>
Reported-by: Jeeja Kp <jeeja.kp@intel.com>
Tested-by: Jeeja Kp <jeeja.kp@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [standalone]

Back to top | Article view | linux.kernel

csiph-web