linux-kernel - Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race with cpuset update

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Message-ID: <20170518090846.GD25462@dhcp22.suse.cz>
Date:   Thu, 18 May 2017 11:08:47 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Christoph Lameter <cl@...ux.com>
Cc:     Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        Li Zefan <lizefan@...wei.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        David Rientjes <rientjes@...gle.com>,
        Hugh Dickins <hughd@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-api@...r.kernel.org
Subject: Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race
 with cpuset update

On Wed 17-05-17 10:25:09, Cristopher Lameter wrote:
> On Wed, 17 May 2017, Michal Hocko wrote:
> 
> > > If you have screwy things like static mbinds in there then you are
> > > hopelessly lost anyways. You may have moved the process to another set
> > > of nodes but the static bindings may refer to a node no longer
> > > available. Thus the OOM is legitimate.
> >
> > The point is that you do _not_ want such a process to trigger the OOM
> > because it can cause other processes being killed.
> 
> Nope. The OOM in a cpuset gets the process doing the alloc killed. Or what
> that changed?
> 
> At this point you have messed up royally and nothing is going to rescue
> you anyways. OOM or not does not matter anymore. The app will fail.

Not really. If you can trick the system to _think_ that the intersection
between mempolicy and the cpuset is empty then the OOM killer might
trigger an innocent task rather than the one which tricked it into that
situation.
-- 
Michal Hocko
SUSE Labs