Patch "ALSA: pcm: Fix lockdep warning with nonatomic PCM ops" has been added to the 4.1-stable tree
Subsystems (2)
This is a note to let you know that I've just added the patch titled
ALSA: pcm: Fix lockdep warning with nonatomic PCM ops
to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-pcm-fix-lockdep-warning-with-nonatomic-pcm-ops.patch
and it can be found in the queue-4.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
Quoted 1 line
From
67756e3191c90e7c0b94b8b2fb63de255b6cd337Mon Sep 17 00:00:00 2001
From: Takashi Iwai <[email protected]>
Date: Fri, 17 Jul 2015 15:22:33 +0200
Subject: ALSA: pcm: Fix lockdep warning with nonatomic PCM ops
From: Takashi Iwai <[email protected]>
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.
--- sound/core/pcm_native.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
sound/core/pcm_native.c +1 -1
@@ -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);
Patches currently in stable-queue which might be from [email protected] are
queue-4.1/alsa-line6-fix-ebusy-error-during-active-monitoring.patch queue-4.1/alsa-hda-add-new-amd-pci-ids-with-proper-driver-caps.patch queue-4.1/alsa-usb-audio-add-midi-support-for-steinberg-mi2-mi4.patch queue-4.1/alsa-hda-apply-fixup-for-another-toshiba-satellite-s50d.patch queue-4.1/alsa-pcm-fix-lockdep-warning-with-nonatomic-pcm-ops.patch queue-4.1/alsa-hda-add-new-gpu-codec-id-0x10de007d-to-snd-hda.patch queue-4.1/alsa-usb-audio-add-db-range-mapping-for-some-devices.patch queue-4.1/alsa-hda-add-headset-mic-support-for-acer-aspire-v5-573g.patch queue-4.1/alsa-hda-apply-a-fixup-to-dell-vostro-5480.patch queue-4.1/alsa-hda-fix-macbook-pro-5-2-quirk.patch queue-4.1/alsa-hda-add-headset-mic-pin-quirk-for-a-dell-device.patch