linux-kernel - Re: [PATCH] cpuset: Enforce that a child's cpus must be a subset of the parent

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Message-ID: <20180530140021.GF3320@localhost.localdomain>
Date:   Wed, 30 May 2018 16:00:21 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Waiman Long <longman@...hat.com>
Cc:     Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kernel-team@...com, pjt@...gle.com, luto@...capital.net,
        Mike Galbraith <efault@....de>, torvalds@...ux-foundation.org,
        Roman Gushchin <guro@...com>,
        Patrick Bellasi <patrick.bellasi@....com>
Subject: Re: [PATCH] cpuset: Enforce that a child's cpus must be a subset of
 the parent

Hi,

On 30/05/18 09:46, Waiman Long wrote:
> It was found that the cpuset.cpus could contain CPUs that are not listed
> in their parent's cpu list as shown by the command sequence below:
> 
>   # echo "+cpuset" >cgroup.subtree_control
>   # mkdir g1
>   # echo 0-5 >g1/cpuset.cpus
>   # mkdir g1/g11
>   # echo "+cpuset" > g1/cgroup.subtree_control
>   # echo 6-11 >g1/g11/cpuset.cpus
>   # grep -R . g1 | grep "\.cpus"
>   g1/cpuset.cpus:0-5
>   g1/cpuset.cpus.effective:0-5
>   g1/g11/cpuset.cpus:6-11
>   g1/g11/cpuset.cpus.effective:0-5
> 
> As the intersection of g11's cpus and that of g1 is empty, the effective
> cpus of g11 is just that of g1. The check in update_cpumask() is now
> corrected to make sure that cpus in a child cpus must be a subset of
> its parent's cpus. The error "write error: Invalid argument" will now
> be reported in the above case.
> 
> Reported-by: Juri Lelli <juri.lelli@...hat.com>
> Signed-off-by: Waiman Long <longman@...hat.com>

Looks like it fixes the bug.

Reviewed-and-Tested-by: Juri Lelli <juri.lelli@...hat.com>

Thanks,

- Juri