linux-kernel - Re: mm: deadlock between get_online_cpus/pcpu

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Message-ID: <20170208122154.GJ5686@dhcp22.suse.cz>
Date:   Wed, 8 Feb 2017 13:21:55 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Christoph Lameter <cl@...ux.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dmitry Vyukov <dvyukov@...gle.com>, Tejun Heo <tj@...nel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        syzkaller <syzkaller@...glegroups.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: mm: deadlock between get_online_cpus/pcpu_alloc

On Wed 08-02-17 13:02:07, Thomas Gleixner wrote:
> On Wed, 8 Feb 2017, Michal Hocko wrote:
[...]
> > [1] http://lkml.kernel.org/r/20170207201950.20482-1-mhocko@kernel.org
> 
> Well, yes. It's simple, but from an RT point of view I really don't like
> it as we have to fix it up again.

I thought that preempt_disable would turn into migrate_disable or
something like that which shouldn't cause too much trouble. Or am I
missing something? Which part of the patch is so RT unfriendly?
-- 
Michal Hocko
SUSE Labs