linux-kernel - Re: [PATCH v2] sched/core: fix illegal RCU from offline CPUs

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Message-Id: <4134872A-3D1D-4860-9C1B-2FD9C00272BB@lca.pw>
Date:   Thu, 2 Apr 2020 12:19:54 -0400
From:   Qian Cai <cai@....pw>
To:     paulmck@...nel.org
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, juri.lelli@...hat.com,
        dietmar.eggemann@....com, vincent.guittot@...aro.org,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        tglx@...utronix.de,
        "James.Bottomley@...senpartnership.com" 
        <James.Bottomley@...senpartnership.com>, deller@....de,
        linuxppc-dev@...ts.ozlabs.org, linux-parisc@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Nicholas Piggin <npiggin@...il.com>
Subject: Re: [PATCH v2] sched/core: fix illegal RCU from offline CPUs



> On Apr 2, 2020, at 11:54 AM, Paul E. McKenney <paulmck@...nel.org> wrote:
> 
> I do run this combination quite frequently, but only as part of
> rcutorture, which might not be a representative workload.  For one thing,
> it has a minimal userspace consisting only of a trivial init program.
> I don't recall having ever seen this.  (I have seen one recent complaint
> about an IPI being sent to an offline CPU, but I cannot prove that this
> was not due to RCU bugs that I was chasing at the time.)

Yes, a trivial init is tough while running systemd should be able to catch it as it will use cgroup.