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SubjectRe: [RFC PATCH v6 3/3] arm: fix a migrating irq bug when hotplug cpu
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Hi Russell,

On Thu, Oct 22, 2015 at 11:26 AM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
> On Wed, Oct 21, 2015 at 09:29:08PM +0100, Russell King - ARM Linux wrote:
>> On Wed, Oct 21, 2015 at 01:47:49PM +0200, Geert Uytterhoeven wrote:
>> > On Thu, Sep 24, 2015 at 11:32 AM, Yang Yingliang
>> > <yangyingliang@huawei.com> wrote:
>> > > When cpu is disabled, all irqs will be migratged to another cpu.
>> > > In some cases, a new affinity is different, the old affinity need
>> > > to be updated and if irq_set_affinity's return value is IRQ_SET_MASK_OK_DONE,
>> > > the old affinity can not be updated. Fix it by using irq_do_set_affinity.
>> > >
>> > > And migrating interrupts is a core code matter, so use the generic
>> > > function irq_migrate_all_off_this_cpu() to migrate interrupts in
>> > > kernel/irq/migration.c.
>> > >
>> > > Cc: Jiang Liu <jiang.liu@linux.intel.com>
>> > > Cc: Thomas Gleixner <tglx@linutronix.de>
>> > > Cc: Marc Zyngier <marc.zyngier@arm.com>
>> > > Cc: Mark Rutland <mark.rutland@arm.com>
>> > > Cc: Will Deacon <will.deacon@arm.com>
>> > > Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
>> > > Cc: Hanjun Guo <hanjun.guo@linaro.org>
>> > > Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
>> > > ---
>> > > arch/arm/Kconfig | 1 +
>> > > arch/arm/include/asm/irq.h | 1 -
>> > > arch/arm/kernel/irq.c | 62 ----------------------------------------------
>> > > arch/arm/kernel/smp.c | 2 +-
>> > > 4 files changed, 2 insertions(+), 64 deletions(-)
>> > >
>> > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> > > index 72ad724..bffba78 100644
>> > > --- a/arch/arm/Kconfig
>> > > +++ b/arch/arm/Kconfig
>> > > @@ -1492,6 +1492,7 @@ config NR_CPUS
>> > > config HOTPLUG_CPU
>> > > bool "Support for hot-pluggable CPUs"
>> > > depends on SMP
>> > > + select GENERIC_IRQ_MIGRATION
>> >
>> > This causes the following warnings during s2ram on r8a7791/koelsch
>> > (dual-core CA15):
>>
>> Thanks for the report. I'll see what tonight's boot run says for my
>> platforms. Hopefully, the author of these changes can help debug
>> this.
>
> What's happened is that:
>
> - c = irq_data_get_irq_chip(d);
> - if (!c->irq_set_affinity)
> - pr_debug("IRQ%u: unable to set affinity\n", d->irq);
>
> has become:
>
> + c = irq_data_get_irq_chip(d);
> + if (!c->irq_set_affinity) {
> + pr_warn_ratelimited("IRQ%u: unable to set affinity\n", d->irq);
>
> which makes things more noisy.
>
> This is a change that was not described in the commit message for the
> patch Thomas merged.
>
> So, I think the right thing to do is to drop the patch set and revert
> back to what we knew was sane, and get the submitter to do the job
> properly: cleanly move the code from one location to another with _no_
> changes what so ever, convert ARM and ARM64 to use it, and _then_ to
> modify the resulting code.
>
> From what I can see, both ARM and ARM64 implementations here are
> identical.
>
> I'm certainly dropping this from the ARM tree.

Thanks for your analysis!

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds


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