[alsa-devel] [pulseaudio-discuss] pulseaudio fails to start with kernel 4.11, caused by new snd_hdmi_lpe_audio module)

[Hans de Goede]

Hi,

On 21-03-17 10:04, Arun Raghavan wrote:
>
>
> On Tue, 21 Mar 2017, at 02:26 PM, Hans de Goede wrote:
>> Hi,
>>
>> On 21-03-17 08:54, Arun Raghavan wrote:
>>> On Tue, 21 Mar 2017, at 11:10 AM, Takashi Iwai wrote:
>>>> On Tue, 21 Mar 2017 00:09:22 +0100,
>>>> Pierre-Louis Bossart wrote:
>>>>>
>>>>> On 3/20/17 4:52 AM, Takashi Iwai wrote:
>>>>>> On Mon, 20 Mar 2017 12:42:58 +0100,
>>>>>> Hans de Goede wrote:
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Lately I've been working on fixing various issues people
>>>>>>> are having with baytrail / cherrytrail devices. One thing
>>>>>>> I noticed when moving my testing / development to 4.11 is
>>>>>>> that pulseaudio does not work (it aborts while starting)
>>>>>>> this seemed to be caused by the new snd_hdmi_lpe_audio
>>>>>>> module. If I blacklist that all is fine. Any idea what
>>>>>>> is causing this ?
>>>>>>
>>>>>> I noticed it once, too, but I had no time to check further.
>>>>>> More interestingly, PA works fine when LPE audio is the single driver
>>>>>> (i.e. blacklist Intel SST instead), too.  So it's more likely a bug in
>>>>>> PA.
>>>>>>
>>>>>> What happens when you modprobe LPE audio driver after starting the
>>>>>> session?  If it kills PA, we can debug more easily :)
>>>>>
>>>>> I've seen this as well, I could get either one of the two but not
>>>>> both, could this be due to the fact that one set of mixers is
>>>>> configured with UCM and the other driver isn't configured by UCM?
>>>>
>>>> No idea, and I had still no time to check (still processing the
>>>> pile of pending mails and other bugs :).  Let me add PA guys to Cc.
>>>
>>> Not sure if anyone here has the hardware and I haven't seen any
>>> complaints either -- having a backtrace (or even location of the assert)
>>> would be a good start.
>>
>> Ok, this is weird. Since you were asking for more info I tried to
>> collect a backtrace / logs. But what is happening is that after
>> the snd_hdmi_lpe_audio module loads, pulse does its thing and
>> then exits with a message of "killed" in gdb / on the terminal
>> from which I started it. I don't get a chance to get a backtrace
>> in gdb ...  So this does feel like a kernel bug to me, normally
>> this sort of "killed" behavior is seen on some kernel oopses...
>>
>> But dmesg is free of any oopses ?
>>
>> Anyways here is a log of pulseaudio -v first without the
>> hdmi module and then the module gets probed. Where the log
>> abruptly ends is where I got the "Killed" message on the
>> terminal.
>
> That's the kernel killing of PA for exceeding RT limits (there's a patch
> in the timers tip that'll now provide an error in dmesg).
>
> It sounds possible that there is some call to the ALSA API that we are
> making that results in the driver blocking for long enough to exceed the
> RT limit. You can verify this by setting 'realtime-scheduling = no' in
> /etc/pulse/daemon.conf and then starting PA.
>
> If that works,

Yep that works, good call.

> perf will likely be able to show you what's blocking.

I'm not all that familiar with perf, can you provide me with
a perf cmdline to start pulseaudio with which will generate a log
file with the info you are looking for ?

Regards,

Hans