Re: bug in Real-Time Preemption

Michal Schmidt
2005-06-10T07:52:42Z

[-- Attachment #1: Type: text/plain, Size: 397 bytes --]

Milan Svoboda wrote:
> under non RT preempt:
> (these results are expected)
>
> ./a.out
> Flag: 0, Dif:11714
> ./a.out
> Flag: 0, Dif:11678
>
> under full RT preempt:
> ./a.out
> Flag: 1, Dif:582536
> ./a.out
> Flag: 1, Dif:579791
>
> This shows that thread with bigger priority was
> blocked by the thread with lower priority!

Can you retry with RT-V0.7.48-05 and this patch applied?

Michal

[-- Attachment #2: rt-fix-delayed-preemption-lags2.diff --]
[-- Type: text/plain, Size: 867 bytes --]

diff -Nurp -X linux-RT/Documentation/dontdiff linux-RT/kernel/sched.c linux-RT.mich/kernel/sched.c
--- linux-RT/kernel/sched.c 2005-06-09 23:09:43.000000000 +0200
+++ linux-RT.mich/kernel/sched.c 2005-06-09 23:29:20.000000000 +0200
@@ -1190,18 +1190,14 @@ out_activate:
* this cpu. Delayed preemption is guaranteed to happen upon
* return to userspace.
*/
- if (cpu != this_cpu) {
+ if (!sync || cpu != this_cpu) {
activate_task(p, rq, cpu == this_cpu);
if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
} else {
__activate_task(p, rq);
- if (TASK_PREEMPTS_CURR(p, rq)) {
- if (sync)
- set_tsk_need_resched_delayed(rq->curr);
- else
- resched_task(rq->curr);
- }
+ if (TASK_PREEMPTS_CURR(p, rq))
+ set_tsk_need_resched_delayed(rq->curr);
}
trace_start_sched_wakeup(p, rq);
if (rq->curr && p && rq && _need_resched())