[pulseaudio-discuss] [PATCH 2/7] don't move streams to devices that are going away

[Tanu Kaskinen]

On Thu, 2016-04-21 at 12:26 +0530, Arun Raghavan wrote:
> On 22 March 2016 at 19:11, Tanu Kaskinen <tanuk at iki.fi> wrote:
> > 
> > Before a device is unlinked, the unlink hook is fired, and it's
> > possible that a routing module tries to move streams to the unlinked
> > device in that hook, because it doesn't know that the device is being
> > unlinked. Of course, the unlinking is obvious when the code is in an
> > unlink hook callback, but it's possible that some other module does
> > something in the unlink hook that in turn triggers some other hook,
> > and it's this second hook where the routing module may get confused.
> > This patch adds an "unlink_requested" flag that is set before the
> > unlink hook is fired, and moving streams to a device with that flag
> > set is prevented.
> > 
> > This patch is motivated by seeing module-device-manager moving a
> > stream to a sink that was being unlinked. It was a complex case where
> > an alsa card was changing its profile, while an echo-cancel sink was
> > connected to the old alsa sink. module-always-sink loaded a null sink
> > in the middle of the profile change, and after a stream had been
> > rescued to the null sink, module-device-manager decided to move it
> > back to the old alsa sink that was being unlinked. That move made no
> > sense, so I came up with this patch.
> > ---
> I think this is a good solution to the problem. Still need to test
> this in a few use cases, but it makes sense to me too.
> 
> I also think that it might be nicer to have this be a part of the
> state enum rather than a separate bool. What do you think? I'm okay to
> make that change quickly if you don't want to, fwiw.

I considered that, but I don't think it's a good idea, because in the
"unlink requested" state the sink is still fully operational, and it
can be running, idle or suspended. Adding a new state would hide the
separation between those states.

-- 
Tanu