Re: [PATCH 2/2] cgroup: make css->refcnt clearing on cgroup removaloptional

[Vivek Goyal]

On Fri, Mar 30, 2012 at 03:36:06PM -0700, Tejun Heo wrote:
> Currently, cgroup removal tries to drain all css references.  If there
> are active css references, the removal logic waits and retries
> ->pre_detroy() until either all refs drop to zero or removal is
> cancelled.
> 
> This semantics is unusual and adds non-trivial complexity to cgroup
> core and IMHO is fundamentally misguided in that it couples internal
> implementation details (references to internal data structure) with
> externally visible operation (rmdir).  To userland, this is a behavior
> peculiarity which is unnecessary and difficult to expect (css refs is
> otherwise invisible from userland), and, to policy implementations,
> this is an unnecessary restriction (e.g. blkcg wants to hold css refs
> for caching purposes but can't as that becomes visible as rmdir hang).

Good to see this patch. Now annyoying rmdir hang with blkcg should be
gone.

Thanks
Vivek
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