Date: Tue, 8 Aug 2017 17:00:34 -0700
From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>, tglx@linutronix.de,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc: xive: ensure active irqd when setting affinity
References: <20170803013822.GD28905@us.ibm.com>
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Michael Ellerman [mpe@ellerman.id.au] wrote:
> Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> writes:
> 
> > From fd0abf5c61b6041fdb75296e8580b86dc91d08d6 Mon Sep 17 00:00:00 2001
> > From: Benjamin Herrenschmidt <benh@kernel.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