On Mon, 08 Jun 2020 12:06:32 +0200, Michał Mirosław wrote:
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@vger.kernel.org Fixes: f57f3df03a8e ("ALSA: pcm: More fine-grained PCM link locking") Signed-off-by: Michał Mirosław mirq-linux@rere.qmqm.pl
Applied now. Thanks.
Takashi