lkml.org 
[lkml]   [2018]   [Jan]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 4.4 20/87] ALSA: pcm: Allow aborting mutex lock at OSS read/write loops
From
Date
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@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.
[...]
> @@ -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.

\
 
 \ /
  Last update: 2018-01-24 00:36    [W:0.288 / U:2.188 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site