linux-kernel - Re: [PATCH v2] isolcpus: affine kernel threads to specified cpumask

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Message-ID: <76fa0270-40c5-aac7-1c53-38384fa3467d@windriver.com>
Date:   Thu, 26 Mar 2020 10:32:51 -0600
From:   Chris Friesen <chris.friesen@...driver.com>
To:     Frederic Weisbecker <frederic@...nel.org>,
        David Laight <David.Laight@...LAB.COM>
Cc:     'Marcelo Tosatti' <mtosatti@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Christoph Lameter <cl@...ux.com>,
        Jim Somerville <Jim.Somerville@...driver.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2] isolcpus: affine kernel threads to specified cpumask

On 3/26/2020 10:22 AM, Frederic Weisbecker wrote:
> On Wed, Mar 25, 2020 at 06:05:27PM +0000, David Laight wrote:

>> How about making it possible to change the default affinity
>> for new kthreads at run time?
>> Is it possible to change the affinity of existing threads?
>> Or maybe only those that didn't specify an explicit one??
> 
> That's already possible yes, most unbound kthreads are accessible
> through /proc including kthreadd from which new kthread will inherit
> their CPU affinity.

Are you sure that the new kthread will inherit the CPU affinity?

__kthread_create_on_node() explicitly sets the new thread as 
SCHED_NORMAL with a mask of "cpu_all_mask".

Chris