A SCHED_FIFO or SCHED_RR task with priority n+1 will not preempt a
running task with priority n. You need to give the higher priority task
a priority of at least n+2 for it to be chosen by the scheduler.
The problem is caused by reschedule_idle(), uniprocessor version:
if (preemption_goodness(tsk, p, this_cpu) > 1)
tsk->need_resched = 1;
For real-time scheduling to work correctly, need_resched should be set
whenever preemption_goodness() is greater than 0, not 1.
Here is a patch against 2.4.3:
--- 2.4.3/kernel/sched.c Thu Apr 19 15:03:21 2001
+++ linux/kernel/sched.c Fri Apr 20 16:45:07 2001
@@ -290,7 +290,7 @@
struct task_struct *tsk;
tsk = cpu_curr(this_cpu);
- if (preemption_goodness(tsk, p, this_cpu) > 1)
+ if (preemption_goodness(tsk, p, this_cpu) > 0)
tsk->need_resched = 1;
#endif
}
Nigel Gamble [EMAIL PROTECTED]
Mountain View, CA, USA. http://www.nrg.org/
MontaVista Software [EMAIL PROTECTED]
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