Hello, Michal. On Fri, Oct 19, 2012 at 03:32:45PM +0200, Michal Hocko wrote: > On Thu 18-10-12 15:41:48, Tejun Heo wrote: > > Hello, Michal. > > > > On Wed, Oct 17, 2012 at 03:30:46PM +0200, Michal Hocko wrote: > > > Now that mem_cgroup_pre_destroy callback doesn't fail finally we can > > > safely move on and forbit all the callbacks to fail. The last missing > > > piece is moving cgroup_call_pre_destroy after cgroup_clear_css_refs so > > > that css_tryget fails so no new charges for the memcg can happen. > > > The callbacks are also called from within cgroup_lock to guarantee that > > > no new tasks show up. We could theoretically call them outside of the > > > lock but then we have to move after CGRP_REMOVED flag is set. > > > > > > Signed-off-by: Michal Hocko <mhocko@xxxxxxx> > > > > So, the plan is to do something like the following once memcg is > > ready. > > > > http://thread.gmane.org/gmane.linux.kernel.containers/22559/focus=75251 > > > > Note that the patch is broken in a couple places but it does show the > > general direction. I'd prefer if patch #3 simply makes pre_destroy() > > return 0 and drop __DEPRECATED_clear_css_refs from mem_cgroup_subsys. > > We can still fail inn #3 without this patch becasuse there are is no > guarantee that a new task is attached to the group. And I wanted to keep > memcg and generic cgroup parts separated. Yes, but all other controllers are broken that way too and the worst thing which will hapen is triggering WARN_ON_ONCE(). Let's note the failure in the commit and remove DEPREDATED_clear_css_refs in the previous patch. Then, I can pull from you, clean up pre_destroy mess and then you can pull back for further cleanups. Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>