Messages in this thread | | | Date | Wed, 21 Jan 2015 16:39:55 +0000 | From | Will Deacon <> | Subject | Re: [Regression] 3.19-rc3 : memcg: Hang in mount memcg |
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On Mon, Jan 19, 2015 at 12:51:27PM +0000, Suzuki K. Poulose wrote: > On 10/01/15 08:55, Vladimir Davydov wrote: > > The problem is that the memory cgroup controller takes a css reference > > per each charged page and does not reparent charged pages on css > > offline, while cgroup_mount/cgroup_kill_sb expect all css references to > > offline cgroups to be gone soon, restarting the syscall if the ref count > > != 0. As a result, if you create a memory cgroup, charge some page cache > > to it, and then remove it, unmount/mount will hang forever. > > > > May be, we should kill the ref counter to the memory controller root in > > cgroup_kill_sb only if there is no children at all, neither online nor > > offline. > > > > Still reproducible on 3.19-rc5 with the same setup.
Yeah, I'm seeing the same failure on my setup too.
> From git bisect, the last good commit is : > > commit 8df0c2dcf61781d2efa8e6e5b06870f6c6785735 > Author: Pranith Kumar <bobby.prani@gmail.com> > Date: Wed Dec 10 15:42:28 2014 -0800 > > slab: replace smp_read_barrier_depends() with lockless_dereference()
So that points at 3e32cb2e0a12 ("mm: memcontrol: lockless page counters") as the offending commit.
Will
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