On Mon, 2018-02-12 at 09:34 +0100, Takashi Iwai wrote:
On Wed, 24 Jan 2018 00:35:48 +0100, Ben Hutchings wrote:
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 patch rather fixes the endless loop: the signal_pending() check is added after goto err, so that it aborts the loop properly.
Let me rephrase then: if snd_pcm_oss_write2() returns 0, does that imply that signal_pending() is true? If there is any other reason that it could return 0, then this appears to introduce a bug.
Ben.