[LAD] JACK and vanilla 3.19.2 startup issue

[Yann Collette]

I meet maybe the same problem under fedora: I added myself to the 
pulse-rt group.
This group has priorities defined in /etc/security/limits.d/95-jack.conf

@jackuser - rtprio 95
@jackuser - memlock unlimited

#@audio    - rtprio 95
#@audio    - memlock unlimited

#@pulse-rt - rtprio 10
#@pulse-rt - nice -20

And because I belong to the jackuser and pulse-rt group, the lower 
rtprio was retained.
If I commented the pulse-rt part of 95-jack.conf everything was back to 
normal.

YC

Le 06/06/2015 16:35, Harry van Haaren a écrit :
> On Sat, Apr 4, 2015 at 8:13 PM, Adrian Knoth 
> <adi at drcomp.erfurt.thur.de <mailto: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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