Re: [PATCH] arm64: fix a migrating irq bug when hotplug cpu

From: Marc Zyngier
Date: Sat Aug 29 2015 - 14:15:18 EST

On 2015-08-29 16:12, Jiang Liu wrote:
On 2015/8/29 21:00, Yang Yingliang wrote:
From: Yang Yingliang <yangyingliang@xxxxxxxxxx>

When cpu is disabled, all irqs will be migratged to another cpu.
In some cases, a new affinity is different, it needed to be coppied
to irq's affinity. But if the type of irq is LPI, it's affinity will
not be coppied because of irq_set_affinity's return value.
So copy the affinity, when the return value is IRQ_SET_MASK_OK_DONE.
Hi Yingliang,
If irq_set_affinity callback returns IRQ_SET_MASK_OK_DONE,
it means that irq_set_affinity has copied the new CPU mask to irq
affinity mask. It would be better to change irq_set_affinity for LPI
to follow this rule.

The main issue here seems to be that we do not call irq_set_affinity, but
that we directly call into the top-level irqchip method, which relies on
the core code to do the copy (see irq_do_set_affinity). Too bad.

It feels like the arm/arm64 code would probably be better consolidated into
kernel/irq/migration.c, which already deals with some of this for x86
and ia64. It would save us the duplication and will make sure we don't
miss things next time we add a new return code, as irq_do_set_affinity
would handle this properly.


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