linux-kernel - Re: [PATCH] stop_machine: Disable preemption after queueing stopper threads

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Message-ID: <alpine.DEB.2.21.1807301913250.1725@nanos.tec.linutronix.de>
Date:   Mon, 30 Jul 2018 19:16:08 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Sodagudi Prasad <psodagud@...eaurora.org>
cc:     Peter Zijlstra <peterz@...radead.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        isaacm@...eaurora.org, matt@...eblueprint.co.uk, mingo@...nel.org,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        pkondeti@...eaurora.org, stable@...r.kernel.org
Subject: Re: [PATCH] stop_machine: Disable preemption after queueing stopper
 threads

On Mon, 30 Jul 2018, Sodagudi Prasad wrote:
> How about including below change as well?  Currently, there is no way to

That would be a completely separate change.

> identify thread migrations completed or not.  When we observe this issue, the
> symptom was work queue lock up. It is better to have some timeout here and
> induce the bug_on.

BUG_ON() is wrong. Why kill the thing if there is at least a theoretical
chance that stuff can continue half baken so you can get more info out of
it. The back trace is pretty much uninteresting.

Thanks,

	tglx