ALSA: pcm: Fix lockdep warning with nonatomic PCM ops
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: NVinod Koul <vinod.koul@intel.com> Reported-by: NJeeja Kp <jeeja.kp@intel.com> Tested-by: NJeeja Kp <jeeja.kp@intel.com> Cc: <stable@vger.kernel.org> Signed-off-by: NTakashi Iwai <tiwai@suse.de>
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