[linux-audio-dev] set_rtlimit problem

[Lee Revell]

On Mon, 2005-11-28 at 10:27 +1030, Jonathan Woithe wrote:
> Hi Lee
> 
> > I just noticed that the sys_get_priority_max and _min syscalls do not
> > take the RT priority rlimit into account.  Since the watchdog thread
> > runs at the -P setting + 10 then if the rlimit is 50 and the user
> > specifies -P50 the watchdog thread will fail.
> > 
> > I believe sched_get_priority_max(SCHED_FIFO) needs to take the rlimit
> > into account - there's no other way to get the upper limit AFAICT.
> 
> I'm not sure what the "set_rtlimit problem" is here - I'm a little confused. 
> In terms of what set_rtlimits does, it seems to me that the watchdog thread
> issue can be easily dealt with: define the max rtpriority value in
> /etc/set_rtlimits to be X, knowing that the maximum jackd "-P" option value
> one can use is X-10.
> 
> Certainly getrlimit()/setrlimit() (which set_rtlimit uses to do its thing)
> seem to take the current rtpriority rlimit into account.  The former
> also returns the rlimit hard limit for the process, which I interpret
> to be the "upper limit" mentioned in the original email.
> 
> In testing I've done during development, set_rtlimits seems to do the right
> thing, based on my understanding of what the right thing is.  If I've
> misunderstood something though I'm happy to be corrected.

Sorry, I should have been clearer.  set_rtlimits (and JACK) are doing
the right thing, I consider this a kernel bug.

Lee