linux-kernel - Re: [patch 1/5] genirq: Delay deactivation in free

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Date:   Fri, 28 Jun 2019 11:28:22 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marc Zyngier <marc.zyngier@....com>
cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Robert Hodaszi <Robert.Hodaszi@...i.com>,
        Vadim Pasternak <vadimp@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-serial@...r.kernel.org
Subject: Re: [patch 1/5] genirq: Delay deactivation in free_irq()

Marc,

On Fri, 28 Jun 2019, Marc Zyngier wrote:
> > --- a/kernel/irq/autoprobe.c
> > +++ b/kernel/irq/autoprobe.c
> > @@ -1699,6 +1700,7 @@ static struct irqaction *__free_irq(stru
> >  	/* If this was the last handler, shut down the IRQ line: */
> >  	if (!desc->action) {
> >  		irq_settings_clr_disable_unlazy(desc);
> > +		/* Only shutdown. Deactivate after synchronize_irq() */
> 
> synchronize_hardirq()

Correct.

> >  
> >  	irq_release_resources(desc);
> The patch makes complete sense, so this comment is only a nit, feel free 
> to ignore me: I find it a bit odd that irq_shutdown() doesn't do the 
> full thing anymore, given that it is the "canonical" function, and that 
> __free_irq is the only one that has special needs. Suggestion below.

We have pretty much the same thing with startup, so I made it symmetric.

> Irrespective of which version you prefer:
> 
> Reviewed-by: Marc Zyngier <marc.zyngier@....com>

Thanks for looking into this!

       tglx