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

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.

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index e317964..c2db7e9 100644 (file)
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1334,8 +1334,11 @@ 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)
@@ -1379,18 +1382,18 @@ 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;
 }
 
@@ -1438,8 +1441,11 @@ 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);
@@ -1470,16 +1476,16 @@ 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;
 }