Re: [PATCH 2/2] cpuset: remove redundant checks in file writefunctions

From: Tejun Heo
Date: Tue Aug 13 2013 - 11:05:58 EST

On Tue, Aug 13, 2013 at 09:17:53AM +0800, Li Zefan wrote:
> Now cgroup core gets a reference to the css when a cgroup file is
> opened(), and the reference is dropped at file release. so it's
> guaranteed the cpuset is online during the write function.

Hmmm... it doesn't really guarantee that as css's can be offlined with
residual css refcnts, os the css may well be offlined by the time it
reaches the rw functions. What's guaranteed is that their refcnts
wouldn't be zero. Eventually we need to implement proper sever
semantics (probably by replacing the custom fs implementation with
sysfs) but right now controllers still need to deal with offline


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