Re: [PATCH v2] cpuset: restore sanity to cpuset_cpus_allowed_fallback()

From: Michal Koutný
Date: Tue May 21 2019 - 10:36:50 EST


On Tue, Apr 09, 2019 at 04:40:03PM -0400, Joel Savitz <jsavitz@xxxxxxxxxx> wrote:
> $ grep Cpus /proc/$$/status
> Cpus_allowed: ff
> Cpus_allowed_list: 0-7

(a)

> $ taskset -p 4 $$
> pid 19202's current affinity mask: f
> pid 19202's new affinity mask: 4
>
> $ grep Cpus /proc/self/status
> Cpus_allowed: 04
> Cpus_allowed_list: 2
>
> # echo off > /sys/devices/system/cpu/cpu2/online
> $ grep Cpus /proc/$$/status
> Cpus_allowed: 0b
> Cpus_allowed_list: 0-1,3
I'm confused where this value comes from, I must be missing something.

Joel, is the task in question put into a cpuset with 0xf CPUs only (at
point (a))? Or are the CPUs 4-7 offlined as well?

Thanks,
Michal