On Mon, 20 Apr 2015 19:20:48 +0200 Peter Zijlstra <pet...@infradead.org> wrote:
> > > + */ > > > + if (preempt_count() & PREEMPT_ACTIVE) > > > + enqueue_pushable_task_preempted(rq, p); > > > + else > > > + enqueue_pushable_task(rq, p); > > > + } > > > } > > This looks wrong, what do you want to find? _any_ preemption? In that > case PREEMPT_ACTIVE is wrong. What you need to check is if the task is > still on the RQ or not. > > If the task was put to sleep it got dequeued, if it was not dequeued, it > got preempted. > > PREEMPT_ACTIVE is only ever set for forced kernel preemption, which is a > special sub case only ever triggered with CONFIG_PREEMPT=y. Ah, you're right. I was thinking of just forced preemption, but, I wasn't thinking about voluntary preemption (preemption points). We want this behavior for that too (for kernel). And yes, if we preempt in user space, this isn't enough either. Actually, I think we only care if the state of the task is TASK_RUNNING, if it is anything else, the task is probably going to sleep anyway and we don't care about FIFO order then. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
