Re: [PATCH] sched_ext: Replace rq_lock() to raw_spin_rq_lock() in scx_ops_bypass()

[Changwoo Min]

Hi Andrea,

Thank you for the review and suggestion!

On 25. 1. 8. 16:16, Andrea Righi wrote:
> Can we include the warning here? In this way people that are hitting the
> same warning can search for it and find this fix.
Sure. I will add the warning message.

> Moreover, we can also add:
>
> Fixes: 0e7ffff1b811 ("scx: Fix raciness in scx_ops_bypass()")
Will add this in the next version.

> Maybe we can also do this here since we're already holding the rq lock and
> irqs are disabled:
>
> 		/* resched to restore ticks and idle state */
> 		if (cpu == smp_processor_id() || cpu_online(cpu))
> 			resched_curr(rq);
>
> >   
> > -		rq_unlock(rq, &rf);
> > +		raw_spin_rq_unlock(rq);
> >   
>
> And remove the following:
>
> >   		/* resched to restore ticks and idle state */
> >   		resched_cpu(cpu);


This optimization makes sense. I will change it as suggested with
one minor change: I will flip the order in the if condition as
follows since cpu_online() is more commonly true:

 		/* resched to restore ticks and idle state */
 		if (cpu_online(cpu) || cpu == smp_processor_id())
 			resched_curr(rq);

Regards,
Changwoo Min