Re: [RFC][PATCH] cgroup: Fix cgroup_subsys::exit callback

[Balbir Singh]

* Peter Zijlstra <peterz@xxxxxxxxxxxxx> [2011-02-07 17:10:33]:

> On Thu, 2011-02-03 at 00:32 +0530, Balbir Singh wrote:
> > > No, just fixed. The callback as it exists isn't useful and leads to
> > > hacks like the above.
> 
> ---
> Subject: cgroup: Fix cgroup_subsys::exit callback
> From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Date: Mon Feb 07 17:02:20 CET 2011
> 
> Make the ::exit method act like ::attach, it is after all very nearly
> the same thing.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> LKML-Reference: <new-submission>
> ---
> Index: linux-2.6/include/linux/cgroup.h
> ===================================================================
> --- linux-2.6.orig/include/linux/cgroup.h
> +++ linux-2.6/include/linux/cgroup.h
> @@ -474,7 +474,8 @@ struct cgroup_subsys {
>  			struct cgroup *old_cgrp, struct task_struct *tsk,
>  			bool threadgroup);
>  	void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
> -	void (*exit)(struct cgroup_subsys *ss, struct task_struct *task);
> +	void (*exit)(struct cgroup_subsys *ss, struct cgroup *cgrp,
> +			struct cgroup *old_cgrp, struct task_struct *task);

The effective change I see

1. mutex_lock() being held
2. Old cgroup being passed as a part of the notification

Is 1 required? I don't see anything in the changelog. For (2), I don't
see it being used, is the use in the scheduler cgroup path/patch?

-- 
	Three Cheers,
	Balbir
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