From: Takashi Iwai Date: Fri, 17 Jul 2015 13:22:33 +0000 (+0200) Subject: ALSA: pcm: Fix lockdep warning with nonatomic PCM ops X-Git-Tag: v4.1.5~84 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=898dbc106e50ab6de4106e2415d0f40e260903c4;p=users%2Fjedix%2Flinux-maple.git ALSA: pcm: Fix lockdep warning with nonatomic PCM ops 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: [] snd_pcm_stream_lock+0x43/0x60 but task is already holding lock: (snd_pcm_link_rwsem){.+.+.+}, at: [] 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 Reported-by: Jeeja Kp Tested-by: Jeeja Kp Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index d126c03361aef..75888dd38a7fc 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);