Re: [RFC PATCH 09/16] sched/fair: core wide cfs task priority comparison(Internet mail)
From: Aaron Lu
Date: Fri Jul 24 2020 - 03:15:14 EST
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.
> 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.