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

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Message-ID: <1502264039.2563.38.camel@kernel.crashing.org>
Date:   Wed, 09 Aug 2017 17:33:59 +1000
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc: xive: ensure active irqd when setting affinity

On Wed, 2017-08-09 at 16:15 +1000, Michael Ellerman wrote:
> I'm not sure I'm convinced. We can't handle every possible case of the
> higher level code calling us in situations we don't expect.
> 
> For example irq_data could be NULL, but we trust the higher level code
> not to do that to us.
> 
> Also I don't see any other driver doing this check.
> 
>   $ git grep irqd_is_started
>   include/linux/irq.h:static inline bool irqd_is_started(struct irq_data *d)
>   kernel/irq/chip.c:      if (irqd_is_started(d)) {
>   kernel/irq/chip.c:      if (irqd_is_started(&desc->irq_data)) {
>   kernel/irq/cpuhotplug.c:        if (irqd_is_per_cpu(d) || !irqd_is_started(d) || !irq_needs_fixup(d)) {

irqd_is_started is brand new so you won't find any :-)

For most cases the problem is a non-issue. Due to how xive works, it's
more of a problem for us because a non-started interrupt has no
targetting information at all.

So this is *somewhat* related to xive internal and I'd rather have
that sanity check in there.

Cheers,
Ben.