Messages in this thread | | | Date | Thu, 15 Jan 2009 09:47:50 +0530 | From | Balbir Singh <> | Subject | Re: [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete |
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* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-01-15 12:24:16]:
> On Wed, 14 Jan 2009 19:25:39 +0530 > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > * Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> [2009-01-14 17:51:21]: > > > > > This is a new one. Please review. > > > > > > === > > > From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> > > > > > > mem_cgroup_get ensures that the memcg that has been got can be accessed > > > even after the directory has been removed, but it doesn't ensure that parents > > > of it can be accessed: parents might have been freed already by rmdir. > > > > > > This causes a bug in case of use_hierarchy==1, because res_counter_uncharge > > > climb up the tree. > > > > > > Check if the memcg is obsolete, and don't call res_counter_uncharge when obsole. > > > > > > Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> > > > > I liked the earlier, EBUSY approach that ensured that parents could > > not go away if children exist. IMHO, the code has gotten too complex > > and has too many corner cases. Time to revisit it. > > > > But I don't like -EBUSY ;) > > When rmdir() returns -EBUSY even if there are no (visible) children and tasks, > our customer will take kdump and send it to me "please explain this kernel bug" > > I'm sure it will happen ;) >
OK, but memory.stat can show why the group is busy and with move_to_parent() such issues should not occur right? I'll relook at the code. Thanks for your input.
-- Balbir
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