linux-kernel - Re: [PATCH] cgroup: Fix potential race between cgroup_exit and cpuset

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Message-ID: <20170831011024.GC491396@devbig577.frc2.facebook.com>
Date:   Wed, 30 Aug 2017 18:10:24 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Neeraj Upadhyay <neeraju@...eaurora.org>
Cc:     lizefan@...wei.com, mingo@...nel.org, longman@...hat.com,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        sramana@...eaurora.org, prsood@...eaurora.org
Subject: Re: [PATCH] cgroup: Fix potential race between cgroup_exit and
 cpuset_attach

Hello,

On Wed, Aug 30, 2017 at 06:23:50PM +0530, Neeraj Upadhyay wrote:
> cpuset_hotplug_workfn()
>   cgroup_transfer_tasks()
>     cgroup_migrate()
>       cgroup_migrate_execute()
>           <TASK EXIT>
>           list_del_init(&task->cg_list)
>         cpuset_attach()
>           cgroup_taskset_first(tset, &css) // css is not set
>           guarantee_online_mems(cs, ...) // data abort

I don't think this can happen anymore.  We lock out task exits during
migration and don't call migration callbacks if there's no tasks to
migrate.

Thanks.

-- 
tejun