linux-kernel - Re: ltp or kvm triggerable lockdep alloc

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Date:   Thu, 22 Oct 2020 18:44:13 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Mike Galbraith <efault@....de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: ltp or kvm triggerable lockdep alloc_pid()  deadlock gripe

On 2020-10-22 07:21:13 [+0200], Mike Galbraith wrote:
> Greetings,
Hi,

> The gripe below is repeatable in two ways here, boot with nomodeset so
> nouveau doesn't steal the lockdep show when I then fire up one of my
> (oink) full distro VM's, or from an ltp directory ./runltp -f cpuset
> with the attached subset of controllers file placed in ./runtest dir.
> 
> Method2 may lead to a real deal deadlock, I've got a crashdump of one,
> stack traces of uninterruptible sleepers attached.

Just added commit
	267580db047ef ("seqlock: Unbreak lockdep")

and it is gone.

Sebastian