[LAU] unable to set scheduling priority with rt kernel

[Fernando Lopez-Lezcano]

On Wed, 2007-10-24 at 15:59 +0300, Chuckk Hubbard wrote:
> Hi doc, thanks for the guess.  sudo chrt does work, though.  I'm
> supposed to not need it with the rt-patched kernel, which allows
> non-root users to set high priorities.

Not exactly right. The rt-patched kernel (Ingo's patches) only optimizes
the max latency paths in the kernel. Other software is what allows
non-root users to use SCHED_FIFO scheduling. There are several options,
the current one is /etc/security/limits.conf through PAM, there are
others. 

-- Fernando


> On 10/24/07, Dragan Noveski <perodog at gmx.net> wrote:
>         chuckk, i can only try to guess.
>         perhaps sudo on your system is not allowed to do chrt?
>         on my system i have the file /etc/sudoers containing this two
>         important
>         lines:
>         
>         root    ALL=(ALL) ALL
>         nowhiskey       ALL=NOPASSWD: ALL 
>         
>         don't know if it could be the root of the problem, because if
>         so, i
>         would expect something like 'operation not permitted' error,
>         but who knows.
>         
>         
>         cheers,
>         doc
>         >
>         > My kernel has: 
>         > # CONFIG_PREEMPT_NONE is not set
>         > # CONFIG_PREEMPT_VOLUNTARY is not set
>         > # CONFIG_PREEMPT_DESKTOP is not set
>         > CONFIG_PREEMPT_RT=y
>         > CONFIG_PREEMPT=y
>         > CONFIG_PREEMPT_SOFTIRQS=y
>         > CONFIG_PREEMPT_HARDIRQS=y
>         > CONFIG_PREEMPT_BKL=y
>         > # CONFIG_CLASSIC_RCU is not set
>         > CONFIG_PREEMPT_RCU=y
>         >
>         > /etc/security/limits.conf has:
>         > @audio         -     nice         -10 
>         > @audio         -     rtprio         99
>         > @audio         -     memlock     4000000 (someone on the
>         jack list
>         > suggested that my previous value "unlimited" was not
>         recognized, so I
>         > stuck this in but no change) 
>         >
>         > and user "chuckk" is in group "audio".
>         >
>         > Lastly, the output from my script when the second sudo chrt
>         line is
>         > commented out:
>         > ------------------------------ 
>         > pid 684's current scheduling policy: SCHED_FIFO
>         > pid 684's current scheduling priority: 82
>         > jackd 0.103.0
>         > Copyright 2001-2005 Paul Davis and others.
>         > jackd comes with ABSOLUTELY NO WARRANTY 
>         > This is free software, and you are welcome to redistribute
>         it
>         > under certain conditions; see the file COPYING for details
>         >
>         > JACK compiled with System V SHM support.
>         > pid 5132's current scheduling policy: SCHED_OTHER 
>         > pid 5132's current scheduling priority: 0
>         > loading driver ..
>         > Enhanced3DNow! detected
>         > SSE2 detected
>         > apparent rate = 44100
>         > creating alsa driver ... hw:0|-|256|2|44100|0|0|nomon 
>         > |swmeter|-|32bit
>         > control device hw:0
>         > configuring for 44100Hz, period = 256 frames, buffer = 2
>         periods
>         > ALSA: final selected sample format for playback: 32bit
>         little-endian
>         > ALSA: use 2 periods for playback 
>         >
>         > --------------------------------------
>         >
>         > Any ideas what I may have missed or misconfigured?
>         >
>         > Thanks!
>         > -Chuckk
>         >
>         >
>         > --
>         > http://www.badmuthahubbard.com
>         >
>         ------------------------------------------------------------------------
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> 
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