Date: Tue, 5 Sep 2017 11:55:47 +0200
From: Markus Trippelsdorf <markus@trippelsdorf.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>
Subject: Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.
 perf
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On 2017.09.05 at 10:53 +0200, Peter Zijlstra wrote:
> On Tue, Sep 05, 2017 at 09:27:38AM +0200, Markus Trippelsdorf wrote:
> > Current mainline git (24e700e291d52bd2) hangs when building software
> > concurrently (for example perf).
> > The issue is not 100% reproducible (sometimes building perf succeeds),
> > so bisecting will not work.
> 
> Sadly I cannot reproduce, I had:
> 
>   while :; do make clean; make; done
> 
> running on tools/perf for a while, and now have:
> 
>   while :; do make O=defconfig-build clean; make O=defconfig-build -j80; done
> 
> running, all smooth sailing, although there's the hope that the moment I
> hit send on this email the box comes unstuck.
> 
> > Magic SysRq key doesn't work and there is nothing in the logs.
> > Enabling CONFIG_PROVE_LOCKING makes the issue go away.
> 
> SysRq not working is suspicious.. and I take it the NMI watchdog also
> isn't firing?

Yes.

> > Any ideas on how to debug this further?
> 
> So you have a (real) serial line on that box?

Sadly, no. But hopefully somebody else (with a proper kernel debugging
setup) will reproduce the issue soon.

-- 
Markus