[pulseaudio-discuss] [PATCH] echo-cancel: Avoid segfaults due to invalid master sink or source

Georg Chini georg at chini.tk
Sat May 6 20:38:33 UTC 2017

On 06.05.2017 22:15, Georg Chini wrote:
> On 06.05.2017 22:06, Tanu Kaskinen wrote:
>> On Sat, 2017-05-06 at 20:06 +0200, Georg Chini wrote:
>>> On 06.05.2017 18:36, Tanu Kaskinen wrote:
>>>> On Fri, 2017-05-05 at 16:21 +0200, Georg Chini wrote:
>>>>> I agree with you that my patch is wrong, but I think there is a 
>>>>> simpler
>>>>> solution than your patch. The reason why the move is triggered at all
>>>>> is because the virtual sink becomes the default sink when no other
>>>>> sink is available. Then a null-sink turns up and the streams are 
>>>>> moved
>>>>> away from the default sink. This does not make sense anyway for a
>>>>> virtual sink, we don't want the streams to move away from there.
>>>>> So the simple fix is to prevent the virtual sink from being the 
>>>>> default
>>>>> sink when it is not connected to a master, then the move will not 
>>>>> occur.
>>>>> If you are OK with that approach, I would send a patch.
>>>> By "the virtual sink", do you mean the null sink? Would you want it to
>>>> be impossible to make any null sink the default sink? That doesn't 
>>>> seem
>>>> like a good idea, so do you propose some more nuanced policy?
>>> No, by virtual sink I mean the filter sink. I think you did not get 
>>> what I
>>> wanted to say. When there is no other sink, the filter sink becomes
>>> the default before the null sink turns up. Then streams are moved
>>> from the moving filter sink to the new null sink. If we prevent the
>>> filter sink from becoming the default while its sink input is moving,
>>> the problem will not happen in the first place.
>>> I'll send a patch, maybe you understand better what I mean then.
>> I made a strange interpretation, because what you really meant seemed
>> even more crazy. I forgot that module-switch-on-connect only moves
>> streams if they are routed to the default sink, and because of that
>> missing piece your explanation made no sense to me at all. I understand
>> the logic now.
>> Implementing your proposal doesn't seem that simple: what if the user
>> has set a filter sink as the default sink? Would you change the default
>>   sink just for the duration of the filter sink move?
> I already implemented it and it is quite simple (using part of your
> patch).
> The default sink will be set to the new sink by switch-on-connect
> anyway (even the configured default sink), so the previous user
> choice is irrelevant. I think however, that the simple logic of
> switch-on-connect should at least be changed so that in the case
> that the previous default sink was a filter then the streams should
> not be moved away from it (unless the new sink also is a filter).
> But this would be a matter of a different patch.
Another advantage of my patch is that you will not end up with failed moves
that might kill the streams.

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