On Tue, 20 Oct 2020 20:02:55 +0200 Thomas Gleixner <[email protected]> wrote:
> On Tue, Oct 20 2020 at 11:38, Steven Rostedt wrote: > > On Tue, 20 Oct 2020 16:46:55 +0200 > > Thomas Gleixner <[email protected]> wrote: > > > >> - /* > >> - * Since we are going to call schedule() anyway, there's > >> - * no need to preempt or enable interrupts: > > > > I think the above comment still makes sense, just needs to be tweeked: > > > > /* > > * Since we are going to call schedule() anyway, there's > > * no need to allow preemption after releasing the rq lock. > >> - */ > > > > Especially, since we are now enabling interrupts, which is likely to > > trigger a preemption. > > sched_preempt_enable_no_resched() still enables preemption. It just > avoids the check. And it still allows preemption when an interrupt > triggering preemption happens between sched_preempt_enable_no_resched() > and __schedule() disabling preemption/interrupts. > > So no, your new variant is just differently bogus and misleading. What I wrote wasn't exactly what I meant. What I meant to have: /* * Since we are going to call schedule() anyways, there's * no need to do the preemption check when the rq_lock is released. */ That is, to document why we have the preempt_disable() before the unlock: preempt_disable(); rq_unlock_irq(rq, &rf); sched_preempt_enable_no_resched(); -- Steve
