linux-kernel - Re: [PATCH 2/4] cpu/hotplug: CPUHP_BRINGUP

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Date:   Wed, 20 Jan 2021 18:30:45 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Donnefort <vincent.donnefort@....com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        valentin.schneider@....com
Subject: Re: [PATCH 2/4] cpu/hotplug: CPUHP_BRINGUP_CPU exception in fail
 injection

On Wed, Jan 20, 2021 at 03:17:24PM +0000, Vincent Donnefort wrote:
> On Wed, Jan 20, 2021 at 01:58:35PM +0100, Peter Zijlstra wrote:
> > On Mon, Jan 11, 2021 at 05:10:45PM +0000, vincent.donnefort@....com wrote:

> > > +	if (cpuhp_is_atomic_state(fail) ||
> > > +	    (fail == CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU))
> > >  		return -EINVAL;
> > 
> > Should we instead disallow failing any state that has .cant_stop ?
> 
> We would reduce the scope of what can be tested: bringup_cpu() and
> takedown_cpu() are both marked as "cant_stop". Still, those callbacks are
> allowed to fail.

Fair enough. I suppose we can add an additional cant_fail field, but I'm
not sure that's worth the effort over this.