linux-kernel - Re: WARNING: possible circular locking dependency detected

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.20.1708311011050.1874@nanos>
Date:   Thu, 31 Aug 2017 10:15:05 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Borislav Petkov <bp@...en8.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: WARNING: possible circular locking dependency detected

On Thu, 31 Aug 2017, Peter Zijlstra wrote:

> On Thu, Aug 31, 2017 at 09:55:57AM +0200, Thomas Gleixner wrote:
> > > Arghh!!!
> > > 
> > > And allowing us to create events for offline CPUs (possible I think, but
> > > maybe slightly tricky) won't solve that, because we're already holding
> > > the hotplug_lock during PREPARE.
> > 
> > There are two ways to cure that:
> > 
> > 1) Have a pre cpus_write_lock() stage which is serialized via
> >    cpus_add_remove_lock, which is the outer lock for hotplug.
> > 
> >    There we can sanely create stuff and fail with all consequences.
> 
> True, if you're willing to add more state to that hotplug thing I'll try
> and make that perf patch that allows attaching to offline CPUs.

Now that I think more about it. That's going to be an interesting exercise
vs. the hotplug state registration which relies on cpus_read_lock()
serialization.....

Thanks,

	tglx