[LAD] JACK and vanilla 3.19.2 startup issue

[Harry van Haaren]

On Sat, Apr 4, 2015 at 8:13 PM, Adrian Knoth <adi at drcomp.erfurt.thur.de>
wrote:

> Not enough information. I recommend starting jackd with strace
>
Done - apologies for the delay. Strace output available[1], but the most
interesting part copied here:

sched_get_priority_min(SCHED_FIFO)      = 1
sched_setscheduler(0, SCHED_FIFO, { 1 }) = -1 EPERM (Operation not
permitted)
write(2, "\nJACK is running in realtime mod"..., 87
JACK is running in realtime mode, but you are not allowed to use realtime
scheduling.
) = 87



> This code tries to call sched_setscheduler() with SCHED_FIFO. My bet is
> that your "almost vanilla kernel" fails to fulfil this request, but
> strace will tell you for sure.
>
By "almost vanilla" I meant the Arch linux packaged version - I didn't
change the config myself (and Arch aims to be true to vanilla). A very
accurace prediction though - indeed sched_setscheduler() is causing a
return of -1. This is running as root though - so something is wrong here.


> The question is why said call should fail. The only thing that comes to
> my mind are CGROUPS. Maybe your old kernel comes without, the new kernel
> supports them and the configuration is set in a way that disables
> SCHED_FIFO by default.
>
Perhaps - I'm not experienced with cgroups or such, if anybody has any test
ideas for me I'll try them out?

Cheers, -Harry

[1] http://openavproductions.com/tmp/straceJackd.txt
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