On Mon, Apr 20, 2015 at 01:48:03PM -0400, Steven Rostedt wrote: > 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.
Please don't try and be clever there :-) Task state can be misleading, you might get a wakeup before you're running again, in which case you never went to sleep. Please use task_on_rq_queued(p) like all other sites. -- 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/
