Re: [PATCH sched_ext/for-6.11] sched_ext: Reverting @p->sched_class if @p->disallow is set

[Tejun Heo <tj@kernel.org>]

Hello,

On Tue, Jul 16, 2024 at 07:32:09PM +0800, Zhangqiao (2012 lab) wrote:
> 在 2024/7/12 2:57, Tejun Heo 写道:
> > On Thu, Jul 11, 2024 at 07:07:20PM +0800, Zhangqiao (2012 lab) wrote:
> > ...
> > >   		if (p->policy == SCHED_EXT) {
> > >   			p->policy = SCHED_NORMAL;
> > > +			p->sched_class = &fair_sched_class;
> > >   			atomic_long_inc(&scx_nr_rejected);
> > Did you see any issues with the existing implementation? The policy is set
> > before the task is attached, so it should work fine. Also, you can't change
> > sched_class by just assigning to it.
> 
> What does "attach" mean? I'm not sure. p->sched_class is assigned in
> __sched_fork() which is performed before scx_ops_init_task().

Ah, I see what you mean. I was referring to the classs switching operations
in scx_ops_enable(). You're looking at the fork path. I don't think we can
switch sched_class at that point and the .disallow mechanism is there to
allow the scheduler to filter out tasks on scheduler start. I'll update the
code so that .disallow is only allowed during the initial attach.

Thanks.

-- 
tejun