linux-kernel - Re: [PATCH 2/2] sched: do not call workqueue sleep hook if task is already dead

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Message-ID: <20161021053920.GW3102@twins.programming.kicks-ass.net>
Date:   Fri, 21 Oct 2016 07:39:20 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Roman Pen <roman.penyaev@...fitbricks.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] sched: do not call workqueue sleep hook if task is
 already dead

On Wed, Sep 21, 2016 at 05:43:50PM +0200, Roman Pen wrote:
> If panic_on_oops is not set and oops happens inside workqueue kthread,
> kernel kills this kthread.  Current patch fixes recursive GPF which
> happens in that case with the following stack:


> The root cause is that zeroed task->vfork_done member is accessed from
> wq_worker_sleeping() hook. 

This is the kthread_data() -> to_kthread() thing? Could've done with
spelling out, now you had me searching all over :/


Urgh what a mess..