On Tue, Oct 02, 2007 at 07:06:32AM +0200, Ingo Molnar wrote:
> Index: linux-rt-rebase.q/kernel/sched.c
> ===================================================================
> --- linux-rt-rebase.q.orig/kernel/sched.c
> +++ linux-rt-rebase.q/kernel/sched.c
> @@ -1819,6 +1819,13 @@ out_set_cpu:
> cpu = task_cpu(p);
> }
>
> +out_activate:
> +#endif /* CONFIG_SMP */
> +
> + activate_task(rq, p, 1);
> +
> + trace_start_sched_wakeup(p, rq);
> +
> /*
> * If a newly woken up RT task cannot preempt the
> * current (RT) task (on a target runqueue) then try
> @@ -1849,28 +1856,21 @@ out_set_cpu:
> smp_send_reschedule_allbutself_cpumask(p->cpus_allowed);
>
> schedstat_inc(this_rq, rto_wakeup);
> - }
> -
> -out_activate:
> -#endif /* CONFIG_SMP */
> -
> - activate_task(rq, p, 1);
> -
> - trace_start_sched_wakeup(p, rq);
> -
> - /*
> - * Sync wakeups (i.e. those types of wakeups where the waker
> - * has indicated that it will leave the CPU in short order)
> - * don't trigger a preemption, if the woken up task will run on
> - * this cpu. (in this case the 'I will reschedule' promise of
> - * the waker guarantees that the freshly woken up task is going
> - * to be considered on this CPU.)
> - */
> - if (!sync || cpu != this_cpu)
> - check_preempt_curr(rq, p);
> - else {
> - if (TASK_PREEMPTS_CURR(p, rq))
> - set_tsk_need_resched_delayed(rq->curr);
> + } else {
> + /*
> + * Sync wakeups (i.e. those types of wakeups where the waker
> + * has indicated that it will leave the CPU in short order)
> + * don't trigger a preemption, if the woken up task will run on
> + * this cpu. (in this case the 'I will reschedule' promise of
> + * the waker guarantees that the freshly woken up task is going
> + * to be considered on this CPU.)
> + */
> + if (!sync || cpu != this_cpu)
> + check_preempt_curr(rq, p);
> + else {
> + if (TASK_PREEMPTS_CURR(p, rq))
> + set_tsk_need_resched_delayed(rq->curr);
> + }
> }
> if (rq->curr && p && rq && _need_resched())
> trace_special_pid(p->pid, PRIO(p), PRIO(rq->curr));
Not an issue with the patch, just that last bit of code pulled in for
context. I don't think it is a bug, but the checking of 'rq' after
checking 'rq->curr' just doesn't look right (or necessary). Could it
just be an artifact from earlier versions of the code?
--
Mike
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