Messages in this thread | | | Date | Thu, 1 Nov 2012 10:16:44 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH 3/8] cgroup: use cgroup_lock_live_group(parent) in cgroup_create() |
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On Wed 31-10-12 10:04:31, Tejun Heo wrote: > Hey, Michal. > > On Wed, Oct 31, 2012 at 04:55:14PM +0100, Michal Hocko wrote: > > > + /* > > > + * Only live parents can have children. Note that the liveliness > > > + * check isn't strictly necessary because cgroup_mkdir() and > > > + * cgroup_rmdir() are fully synchronized by i_mutex; however, do it > > > + * anyway so that locking is contained inside cgroup proper and we > > > + * don't get nasty surprises if we ever grow another caller. > > > + */ > > > + if (!cgroup_lock_live_group(parent)) { > > > + err = -ENODEV; > > > + goto err_free; > > > + } > > > + > > > > I think this should be moved up before we try to allocate any memory. > > Or is your motivation to keep cgroup_lock held for shorter time? > > I could agree with that but a small comment would be helpful. > > Then I have to change the error out path more and I'm not sure I wanna > call deactivate_super() under cgroup_mutex. It's just simpler this > way.
I am not sure I understand. What does deactivate_super has to do with the above suggestion? cgroup_lock_live_group will take the cgroup_mutex on the success or frees the previously allocated&unused memory. The only thing I was suggesting is to do cgroup_lock_live_group first and allocate the cgroup only if it doesn't fail.
-- Michal Hocko SUSE Labs
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