linux-kernel - Re: [PATCH RT v2] Fix a lockup in wait_for

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Date:   Mon, 1 Jul 2019 15:43:25 -0500
From:   Corey Minyard <cminyard@...sta.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Corey Minyard <minyard@....org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>, tglx@...utronix.de
Subject: Re: [PATCH RT v2] Fix a lockup in wait_for_completion() and friends

On Mon, Jul 01, 2019 at 04:18:40PM -0400, Steven Rostedt wrote:
> On Mon, 1 Jul 2019 14:09:49 -0500
> Corey Minyard <minyard@....org> wrote:
> 
> > On Fri, Jun 28, 2019 at 09:49:03PM -0400, Steven Rostedt wrote:
> > > On Fri, 10 May 2019 12:33:18 +0200
> > > Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:
> 
> > > 
> > > When I applied this patch to 4.19-rt, I get the following lock up:  
> > 
> > I was unable to reproduce, and I looked at the code and I can't really
> > see a connection between this change and this crash.
> > 
> > Can you reproduce at will?  If so, can you send a testcase?
> > 
> 
> Yes, it wont boot. There is no testcase as I don't even make it to a
> boot prompt. I applied the patch and it crashes, I remove the patch and
> it boots without issue.
> 
> Attached is the full dmesg and the config used. I applied it to
> 
>   ae97a0ba0197fb424008a317b79bebacd6a50213
>   Linux 4.19.56-rt23
> 
> It works fine for 5.0.14-rt9 where it was added.
> 
> -- Steve

I show that patch is already applied at

    1921ea799b7dc561c97185538100271d88ee47db
    sched/completion: Fix a lockup in wait_for_completion()

git describe --contains 1921ea799b7dc561c97185538100271d88ee47db
v4.19.37-rt20~1

So I'm not sure what is going on.

-corey