linux-kernel - Re: [PATCH] workqueue: fix selection of wake_cpu in kick

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Message-ID: <yt9djzkvfc6a.fsf@linux.ibm.com>
Date: Thu, 18 Apr 2024 07:54:37 +0200
From: Sven Schnelle <svens@...ux.ibm.com>
To: Tejun Heo <tj@...nel.org>
Cc: Lai Jiangshan <jiangshanlai@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: fix selection of wake_cpu in kick_pool()

Tejun Heo <tj@...nel.org> writes:

> Hello,
>
> On Wed, Apr 17, 2024 at 05:36:38PM +0200, Sven Schnelle wrote:
>> > This generally seems like a good idea but isn't this still racy? The CPU may
>> > go down between setting p->wake_cpu and wake_up_process().
>> 
>> Don't know without reading the source, but how does this code normally
>> protect against that?
>
> Probably by wrapping determining the wake_cpu and the wake_up inside
> cpu_read_lock() section.

Thanks. Should i send a v2 and incorporate your additional changes or do
you want to do that?