This is a note to let you know that I've just added the patch titled

ALSA: pcm: Allow aborting mutex lock at OSS read/write loops

to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: alsa-pcm-allow-aborting-mutex-lock-at-oss-read-write-loops.patch and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 900498a34a3ac9c611e9b425094c8106bdd7dc1c Mon Sep 17 00:00:00 2001

From: Takashi Iwai tiwai@suse.de Date: Mon, 8 Jan 2018 14:03:53 +0100 Subject: ALSA: pcm: Allow aborting mutex lock at OSS read/write loops

From: Takashi Iwai tiwai@suse.de

commit 900498a34a3ac9c611e9b425094c8106bdd7dc1c upstream.

PCM OSS read/write loops keep taking the mutex lock for the whole read/write, and this might take very long when the exceptionally high amount of data is given. Also, since it invokes with mutex_lock(), the concurrent read/write becomes unbreakable.

This patch tries to address these issues by replacing mutex_lock() with mutex_lock_interruptible(), and also splits / re-takes the lock at each read/write period chunk, so that it can switch the context more finely if requested.

Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- sound/core/oss/pcm_oss.c | 36 +++++++++++++++++++++--------------- 1 file changed, 21 insertions(+), 15 deletions(-)

--- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -1370,8 +1370,11 @@ static ssize_t snd_pcm_oss_write1(struct

if ((tmp = snd_pcm_oss_make_ready(substream)) < 0) return tmp; - mutex_lock(&runtime->oss.params_lock); while (bytes > 0) { + if (mutex_lock_interruptible(&runtime->oss.params_lock)) { + tmp = -ERESTARTSYS; + break; + } if (bytes < runtime->oss.period_bytes || runtime->oss.buffer_used > 0) { tmp = bytes; if (tmp + runtime->oss.buffer_used > runtime->oss.period_bytes) @@ -1415,18 +1418,18 @@ static ssize_t snd_pcm_oss_write1(struct xfer += tmp; if ((substream->f_flags & O_NONBLOCK) != 0 && tmp != runtime->oss.period_bytes) - break; + tmp = -EAGAIN; } + err: + mutex_unlock(&runtime->oss.params_lock); + if (tmp < 0) + break; if (signal_pending(current)) { tmp = -ERESTARTSYS; - goto err; + break; } + tmp = 0; } - mutex_unlock(&runtime->oss.params_lock); - return xfer; - - err: - mutex_unlock(&runtime->oss.params_lock); return xfer > 0 ? (snd_pcm_sframes_t)xfer : tmp; }

@@ -1474,8 +1477,11 @@ static ssize_t snd_pcm_oss_read1(struct

if ((tmp = snd_pcm_oss_make_ready(substream)) < 0) return tmp; - mutex_lock(&runtime->oss.params_lock); while (bytes > 0) { + if (mutex_lock_interruptible(&runtime->oss.params_lock)) { + tmp = -ERESTARTSYS; + break; + } if (bytes < runtime->oss.period_bytes || runtime->oss.buffer_used > 0) { if (runtime->oss.buffer_used == 0) { tmp = snd_pcm_oss_read2(substream, runtime->oss.buffer, runtime->oss.period_bytes, 1); @@ -1506,16 +1512,16 @@ static ssize_t snd_pcm_oss_read1(struct bytes -= tmp; xfer += tmp; } + err: + mutex_unlock(&runtime->oss.params_lock); + if (tmp < 0) + break; if (signal_pending(current)) { tmp = -ERESTARTSYS; - goto err; + break; } + tmp = 0; } - mutex_unlock(&runtime->oss.params_lock); - return xfer; - - err: - mutex_unlock(&runtime->oss.params_lock); return xfer > 0 ? (snd_pcm_sframes_t)xfer : tmp; }

Patches currently in stable-queue which might be from tiwai@suse.de are

queue-3.18/alsa-pcm-remove-incorrect-snd_bug_on-usages.patch queue-3.18/alsa-aloop-fix-inconsistent-format-due-to-incomplete-rule.patch queue-3.18/alsa-pcm-add-missing-error-checks-in-oss-emulation-plugin-builder.patch queue-3.18/alsa-pcm-abort-properly-at-pending-signal-in-oss-read-write-loops.patch queue-3.18/alsa-pcm-allow-aborting-mutex-lock-at-oss-read-write-loops.patch queue-3.18/alsa-aloop-fix-racy-hw-constraints-adjustment.patch queue-3.18/alsa-aloop-release-cable-upon-open-error-path.patch