From: Takashi Iwai <tiwai@suse.de>
Date: Mon, 8 Jan 2018 13:03:53 +0000 (+0100)
Subject: ALSA: pcm: Allow aborting mutex lock at OSS read/write loops
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=84f7438d82337ab4cbb9f04d031a0005514f78b3;hp=60c444b1c6af1cc3e0b34da57a5dd2d96d2d6da2;ds=sidebyside

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

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: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index a02512b79085..15ae27863d02 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1375,8 +1375,11 @@ static ssize_t snd_pcm_oss_write1(struct snd_pcm_substream *substream, const cha
 
 	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)
@@ -1420,18 +1423,18 @@ static ssize_t snd_pcm_oss_write1(struct snd_pcm_substream *substream, const cha
 			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;
 }
 
@@ -1479,8 +1482,11 @@ static ssize_t snd_pcm_oss_read1(struct snd_pcm_substream *substream, char __use
 
 	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);
@@ -1511,16 +1517,16 @@ static ssize_t snd_pcm_oss_read1(struct snd_pcm_substream *substream, char __use
 			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;
 }