Re: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.43-00

[Esben Nielsen <simlo@phys.au.dk>]

On Mon, 4 Apr 2005, Steven Rostedt wrote:

> On Mon, 2005-04-04 at 22:47 +0200, Ingo Molnar wrote:
> 
> > > Currently my fix is in yield to lower the priority of the task calling 
> > > yield and raise it after the schedule.  This is NOT a proper fix. It's 
> > > just a hack so I can get by it and test other parts.
> > 
> > yeah, yield() is a quite RT-incompatible concept, which could livelock 
> > an upstream kernel just as much - if the task in question is SCHED_FIFO.  
> > Almost all yield() uses should be eliminated from the upstream kernel, 
> > step by step.
> 
> Now the question is, who will fix it? Preferably the maintainers, but I
> don't know how much of a priority this is to them. I don't have the time
> now to look at this and understand enough about the code to be able to
> make a proper fix, and I'm sure you have other things to do too.

How about adding a
 if(rt_task(current)) {
        WARN_ON(1);
        mutex_setprio(current, MAX_PRIO-1)
 }
?

to find all calls to yields from rt-tasks. That will force the user (aka
the real-time developer) to either stop calling the subsystems still using
yield from his RT-tasks, or fix those subsystems.

Esben

> 
> -- Steve
> 


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