linux-kernel - Re: [PATCH] workqueue: don't use wq_select_unbound

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Message-ID: <20200212210832.GB80993@mtj.thefacebook.com>
Date:   Wed, 12 Feb 2020 16:08:32 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>
Cc:     Lai Jiangshan <jiangshanlai@...il.com>,
        Hillf Danton <hdanton@...a.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: don't use wq_select_unbound_cpu() for bound
 works

On Fri, Jan 24, 2020 at 08:14:45PM -0500, Daniel Jordan wrote:
> From: Hillf Danton <hdanton@...a.com>
> 
> wq_select_unbound_cpu() is designed for unbound workqueues only, but
> it's wrongly called when using a bound workqueue too.
> 
> Fixing this ensures work queued to a bound workqueue with
> cpu=WORK_CPU_UNBOUND always runs on the local CPU.
> 
> Before, that would happen only if wq_unbound_cpumask happened to include
> it (likely almost always the case), or was empty, or we got lucky with
> forced round-robin placement.  So restricting
> /sys/devices/virtual/workqueue/cpumask to a small subset of a machine's
> CPUs would cause some bound work items to run unexpectedly there.
> 
> Fixes: ef557180447f ("workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs")
> Signed-off-by: Hillf Danton <hdanton@...a.com>
> [dj: massage changelog]
> Signed-off-by: Daniel Jordan <daniel.m.jordan@...cle.com>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Lai Jiangshan <jiangshanlai@...il.com>
> Cc: linux-kernel@...r.kernel.org

Applied to wq/for-5.6-fixes.

Thanks.

-- 
tejun