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Patch "ALSA: pcm: Allow aborting mutex lock at OSS read/write loops" has been added to the 4.14-stable tree

PATCH [email protected] 1 participant 1 message Jan 11, 2018

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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 4.14-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-allow-aborting-mutex-lock-at-oss-read-write-loops.patch
and it can be found in the queue-4.14 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 900498a34a3ac9c611e9b425094c8106bdd7dc1c Mon Sep 17 00:00:00 2001

From: Takashi Iwai <[email protected]>
Date: Mon, 8 Jan 2018 14:03:53 +0100
Subject: ALSA: pcm: Allow aborting mutex lock at OSS read/write loops

From: Takashi Iwai <[email protected]>

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 <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 sound/core/oss/pcm_oss.c |   36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)
sound/core/oss/pcm_oss.c +21 -15
@@ -1334,8 +1334,11 @@ 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)

@@ -1379,18 +1382,18 @@ 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;
 }
 

@@ -1438,8 +1441,11 @@ 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);

@@ -1470,16 +1476,16 @@ 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 [email protected] are

queue-4.14/alsa-pcm-remove-incorrect-snd_bug_on-usages.patch queue-4.14/alsa-aloop-fix-inconsistent-format-due-to-incomplete-rule.patch queue-4.14/alsa-pcm-workaround-for-weird-pulseaudio-behavior-on-rewind-error.patch queue-4.14/alsa-pcm-add-missing-error-checks-in-oss-emulation-plugin-builder.patch queue-4.14/alsa-pcm-abort-properly-at-pending-signal-in-oss-read-write-loops.patch queue-4.14/alsa-pcm-allow-aborting-mutex-lock-at-oss-read-write-loops.patch queue-4.14/alsa-aloop-fix-racy-hw-constraints-adjustment.patch queue-4.14/alsa-aloop-release-cable-upon-open-error-path.patch