linux-kernel - Re: [PATCH 3/4] cpu/hotplug: Add cpuhp_invoke_callback

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Message-ID: <YAhuHdcfKnyWKdka@hirez.programming.kicks-ass.net>
Date:   Wed, 20 Jan 2021 18:53:33 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     vincent.donnefort@....com
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        valentin.schneider@....com
Subject: Re: [PATCH 3/4] cpu/hotplug: Add cpuhp_invoke_callback_range()

On Wed, Jan 20, 2021 at 06:45:16PM +0100, Peter Zijlstra wrote:
> On Mon, Jan 11, 2021 at 05:10:46PM +0000, vincent.donnefort@....com wrote:
> > @@ -475,6 +478,11 @@ cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
> >  static inline void
> >  cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
> >  {
> > +	st->target = prev_state;
> > +
> > +	if (st->rollback)
> > +		return;
> 
> I'm thinking that if we call rollback while already rollback we're hosed
> something fierce, no?
> 
> That like going up, failing, going back down again, also failing, giving
> up in a fiery death.

Ooh, is this a hack for _cpu_down():

	ret = cpuhp_down_callbacks(cpu, st, target);
	if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
		cpuhp_reset_state(st, prev_state);
		__cpuhp_kick_ap(st);
	}

Where cpuhp_down_callbacks() can already have called cpuhp_reset_state() ?