Re: [RFC PATCH 09/16] sched/fair: core wide cfs task priority comparison(Internet mail)

[Aaron Lu]

On Wed, Jul 22, 2020 at 12:23:44AM +0000, benbjiang(èå) wrote:
> 
> 
> > +/*
> > + * This function takes care of adjusting the min_vruntime of siblings of
> > + * a core during coresched enable/disable.
> > + * This is called in stop machine context so no need to take the rq lock.
> Hi,
> 
> IMHO, it seems that stop machine context cannot guarantee race free. The param *cpu* maybe not *this_cpu*, rq lock should be taken even in stop machine context, and irq should be disabled too, to avoid potential races with other contexts.
> 

In stop machine context, all CPUs except the active ones are spinning
with irq disabled and in this invocation of stop_machine(), only one
CPU is active so I don't think race is possible.