Re: [PATCH] cgroup: fix dentry still in use bug when dropping cssrefs after umount

From: Tejun Heo
Date: Mon Jul 16 2012 - 12:45:29 EST


On Tue, Jul 10, 2012 at 10:11:05AM +0800, Li Zefan wrote:
> Right, but that should be safe. The css objects of the root cgroup are
> allocated at boot, and won't be destroyed at umount.
> Furthermore when a cgroup hierarchy is going to be unmounted, those css's
> will be made to point to a cgroup named dummytop in rebind_subsystems(),
> and there's a syncronize_rcu() in the end of the function, so accessing
> css->cgroup is always safe.
> In this case, dummytop->dentry is NULL, and that's safe too, because
> cgroup_path() is aware of this case.

I see. Thanks for the explanation.

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