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Date: Wed, 13 Jun 2018 12:50:57 -0700 From: Roman Gushchin <guro@...com> To: John Stultz <john.stultz@...aro.org> CC: Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...e.com>, lkml <linux-kernel@...r.kernel.org> Subject: Re: OOPSes in mem_cgroup_protected On Wed, Jun 13, 2018 at 12:40:23PM -0700, John Stultz wrote: > On Tue, Jun 12, 2018 at 9:33 PM, Roman Gushchin <guro@...com> wrote: > > On Tue, Jun 12, 2018 at 09:08:27PM -0700, John Stultz wrote: > >> On Tue, Jun 12, 2018 at 6:02 PM, John Stultz <john.stultz@...aro.org> wrote: > >> > Hey Tejun, > >> > With the current linus/master, I'm able to fairly regularly trip > >> > OOPSes (two examples below) in mem_cgroup_protected(), which seems to > >> > be new. I haven't managed to trigger this sort of thing with v4.17. > >> > > >> > I've not had much time to dig in or bisect it - I only know that > >> > enabling most of the memory debuging config options didn't seem to > >> > trip anything prior to the issue. So I wanted to send you a heads up > >> > to see if there was already known, or if there was anything you might > >> > suggest to help chase this down. > >> > >> > >> So the line where we're crashing seems to be in mem_cgroup_protected(): > >> parent_emin = READ_ONCE(parent->memory.emin); > >> > >> where I'm guessing the parent->memory value is null, and emin is at > >> the 0x120 offset in the strucutre. > >> > >> Reverting the following commits seems to avoid the issue. > >> bf8d5d52ffe8 ("memcg: introduce memory.min") > >> 5f93ad67436b ("mm: treat memory.low value inclusive") > >> 230671533d64 ("mm: memory.low hierarchical behavior") > >> > >> I'm guessing I'm tripping over some path where the memory value never > >> gets initialized? > >> > >> Any ideas or suggestions? > > > > Hi, John! > > > > The patch below should fix the problem. > > It's in the mm tree right now, and hopefully will be merged upstream asap. > > Sorry for the inconvenience. > > No worries, thanks for the quick fix! The patch you sent seems to be > working well! Perfect, thanks!
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