Re: [PATCH 2/5] cgroup, memcg, cpuset: implement cgroup_taskset_for_each_leader()

From: Tejun Heo
Date: Mon Sep 14 2015 - 16:49:16 EST


On Fri, Sep 11, 2015 at 03:00:19PM -0400, Tejun Heo wrote:
> It wasn't explicitly documented but, when a process is being migrated,
> cpuset and memcg depend on cgroup_taskset_first() returning the
> threadgroup leader; however, this approach is somewhat ghetto and
> would no longer work for the planned multi-process migration.
>
> This patch introduces explicit cgroup_taskset_for_each_leader() which
> iterates over only the threadgroup leaders and replaces
> cgroup_taskset_first() usages for accessing the leader with it.
>
> This prepares both memcg and cpuset for multi-process migration. This
> patch also updates the documentation for cgroup_taskset_for_each() to
> clarify the iteration rules and removes comments mentioning task
> ordering in tasksets.
>
> v2: A previous patch which added threadgroup leader test was dropped.
> Patch updated accordingly.
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Acked-by: Zefan Li <lizefan@xxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxx>

Michal, if you're okay with this patch, I'll apply the patchset in
cgroup/for-4.4.

Thanks.

--
tejun
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