On Mon, 2018-01-15 at 13:34 +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Takashi Iwai <tiwai@xxxxxxx>
>
> 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.
[...]
> @@ -1414,18 +1417,18 @@ 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;
> }
[...]
Some of the "goto err" statements in the loop are conditional on tmp <=
0, but if tmp == 0 this will no longer terminate the loop. Is that
intentional or a bug?
The same for snd_pcm_oss_read1().
Ben.
--
Ben Hutchings
Software Developer, Codethink Ltd.