Re: ltp or kvm triggerable lockdep alloc_pid() deadlock gripe

From: Sebastian Andrzej Siewior
Date: Thu Oct 22 2020 - 12:44:18 EST


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