linux-kernel - Re: [PATCH] powerpc: xive: ensure active irqd when setting affinity

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Date:   Tue, 8 Aug 2017 17:00:34 -0700
From:   Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc: xive: ensure active irqd when setting affinity

Michael Ellerman [mpe@...erman.id.au] wrote:
> Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com> writes:
> 
> > From fd0abf5c61b6041fdb75296e8580b86dc91d08d6 Mon Sep 17 00:00:00 2001
> > From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> > Date: Tue, 1 Aug 2017 20:54:41 -0500
> > Subject: [PATCH] powerpc: xive: ensure active irqd when setting affinity
> >
> > Ensure irqd is active before attempting to set affinity. This should
> > make the set affinity code more robust. For instance, this prevents
> > these messages seen on a 4.12 based kernel when taking cpus offline:
> >
> >    [  123.053037264,3] XIVE[ IC 00  ] ISN 2 lead to invalid IVE !
> >    [   77.885859] xive: Error -6 reconfiguring irq 17
> >    [   77.885862] IRQ17: set affinity failed(-6).
> >
> > The underlying problem with taking cpus offline was fixed in 4.13-rc1 by:
> >
> >    commit 91f26cb4cd3c ("genirq/cpuhotplug: Do not migrated shutdown irqs")
> 
> So do we still need this? Or is the above only a partial fix?

It would be good to have this fix.

Commit 91f26cb4cd3c fixes the problem, so we wont see the errors with
that commit applied. But if such a problem were to show up again, xive
will handle them earlier before hitting those errors.

Sukadev

> 
> I'm a bit confused.
> 
> cheers