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SubjectRe: sched: Reenable interrupts in do sched_yield()
On Wed, 21 Oct 2020 09:27:22 +0200
Thomas Gleixner <tglx@linutronix.de> wrote:

> On Tue, Oct 20 2020 at 16:07, Steven Rostedt wrote:
> > On Tue, 20 Oct 2020 20:02:55 +0200
> > Thomas Gleixner <tglx@linutronix.de> wrote:
> > 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:
>
> which is pretty obvious, but I let Peter decide on that.

To us maybe, but I like to have comments that explain why things are done to
average people. ;-)

If I go to another kernel developer outside the core kernel, would they know
why there's a preempt_disable() there?


preempt_disable();
rq_unlock_irq(rq, &rf);
sched_preempt_enable_no_resched();

schedule();


Not everyone knows that the rq_unlock_irq() would trigger a schedule if an
interrupt happened as soon as irqs were enabled again and need_resched was
set.

-- Steve

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