linux-kernel - Re: [PATCH v5 3/3] irqchip/loongson-eiointc: Refine irq affinity setting during resume

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Message-ID: <87plvynw5b.ffs@tglx>
Date: Wed, 13 Mar 2024 13:39:28 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Bibo Mao <maobibo@...ngson.cn>, Jiaxun Yang <jiaxun.yang@...goat.com>,
 linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org, Sergey Shtylyov
 <s.shtylyov@....ru>, lvjianmin@...ngson.cn
Subject: Re: [PATCH v5 3/3] irqchip/loongson-eiointc: Refine irq affinity
 setting during resume

On Wed, Mar 13 2024 at 14:20, Huacai Chen wrote:
> On Tue, Feb 13, 2024 at 5:49 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>>
>> On Tue, Jan 30 2024 at 16:27, Bibo Mao wrote:
>> > During suspend and resume, CPUs except CPU0 can be hot-unpluged and IRQs
>> > will be migrated to CPU0. So it is not necessary to restore irq affinity
>> > for eiointc irq controller when system resumes.
>>
>> That's not the reason. The point is that eiointc_router_init() which is
>> invoked in the resume path affines all interrupts to CPU0, so the
>> restore operation is redundant, no?
> I'm sorry for the late response but I think this is a little wrong.
> When irq_migrate_all_off_this_cpu() is called at hot-unplug, if an
> irqdesc is irqd_affinity_is_managed() then its affinity is untouched
> (doesn't change to CPU0). Then after resume we should not keep its
> affinity on CPU0 set by eiointc_router_init() , but need to restore
> its old affinity.

Affinity is restored when the interrupt is started up again, so yes the
affinity setting should not be changed.