Re: O(1) scheduler seems to lock up on sched_FIFO and sched_RR tasks

[george anzinger <george@mvista.com>]

Joe Korty wrote:
> On Wed, Jun 18, 2003 at 09:47:24AM -0700, george anzinger wrote:
> 
>>It seems that once a SCHED_FIFO or SCHED_RR tasks gets control it does 
>>not yield to other tasks of higher priority.
>>
>>Attached is a test program (busyloop) that just loops doing 
>>gettimeofday() for the requested time and a little utility (rt) to run 
>>programs at real time priorities.
>>
>>Here is an annotated example of the problem:
>>
>>First, become root then:
>>
>>>rt 90 bash        <-- run bash at priority 90 SCHED_RR
>>>rt -f 30 busyloop 10 &  <-- busyloop 10 at priority 30 SCHED_FIFO
>>
>>At this point the bash at priority 90 should be available, but is not. 
>> When the 10 second busyloop completes, bash returns.
> 
> 
> 
> Hi George,
>  When I boost the priority of each of the per-cpu 'events/%d' daemon to
> 96, the problem goes away.

Seems like your saying that the events workqueues are involved in the 
scheduler in some ugly way.  Certainly not what your average rt 
programmer would expect :(  What is going on here?

> 
> Joe
> -
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-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml