[PATCH 3.2 090/140] ALSA: pcm: Allow aborting mutex lock at OSS read/write loops

Ben Hutchings
2018-02-28T17:31:26Z

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: Ben Hutchings <ben@decadent.org.uk>
---
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
@@ -1375,8 +1375,11 @@ 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)
@@ -1420,18 +1423,18 @@ 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;
}

@@ -1479,8 +1482,11 @@ 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);
@@ -1511,16 +1517,16 @@ 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;
}