linux-kernel - Re: [PATCH 3/4] sched: WARN when migrating to an offline CPU

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Date:   Thu, 28 Sep 2017 13:42:49 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Cc:     Sasha Levin <levinsasha928@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] sched: WARN when migrating to an offline CPU

On Thu, Sep 28, 2017 at 11:03:10AM +0000, Levin, Alexander (Sasha Levin) wrote:
> On Thu, Sep 28, 2017 at 12:35:41PM +0200, Peter Zijlstra wrote:
> >On Thu, Sep 28, 2017 at 02:14:15AM -0700, Sasha Levin wrote:

> >> [2035565360.446794] Unregister pv shared memory for cpu 2
> >> [2035565360.467930] numa_remove_cpu cpu 2 node 2: mask now 6
> >> [2035565360.471431] ------------[ cut here ]------------
> >> [2035565360.472548] WARNING: CPU: 2 PID: 24 at > kernel/sched/core.c:1178 set_task_cpu (kernel/sched/core.c:1157)
> >> [2035565360.473840] Modules linked in:
> >> [2035565360.474632] CPU: 2 PID: 24 Comm: migration/2 Not tainted > 4.14.0-rc2-next-20170927+ #252
> >
> >Urgh, weird. That really shouldn't happen. Can you easily reproduce?
> 
> Looks like yes. Seems like it's enough to stress CPU hotplug + trinity.

OK, I'll see if I can reproduce building kernels and hotplug stress.
Otherwise I'll try and cook up some debug patches for you.