linux-kernel - Re: [patch-3.18.7-rt1] sched/context-tracking: fix PREEMPT

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: <1425980136.3507.17.camel@gmail.com>
Date:	Tue, 10 Mar 2015 10:35:36 +0100
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	linux-rt-users <linux-rt-users@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>, rostedt@...dmis.org,
	John Kacur <jkacur@...hat.com>
Subject: Re: [patch-3.18.7-rt1] sched/context-tracking: fix PREEMPT_LAZY
 explosions

On Mon, 2015-03-09 at 15:36 +0100, Mike Galbraith wrote:
> On Mon, 2015-03-09 at 14:45 +0100, Sebastian Andrzej Siewior wrote:
> > * Mike Galbraith | 2015-02-18 12:21:54 [+0100]:
> > 
> > >On Mon, 2015-02-16 at 12:18 +0100, Sebastian Andrzej Siewior wrote:
> > >
> > >> Known issues:
> > >>
> > >>       - lazy preempt on x86_64 leads to a crash with some load.
> > >
> > >The below still works for me.  (it doesn't make nohz_full actually work
> > >in rt, but at least folks who want to tinker with it can do so)
> > So your box still crashes without it?
> > 
> > The thing is I tried to reproduce it and it does not occur anymore.
> > Neither in KVM nor on real HW.
> 
> Heh, well that's interesting, I just presumed it would still explode
> because you said it would.  I'll beat on it any let you know if I'm
> carrying a placebo patch or not :)

Yup, someone made kaboom go away.  I was able to easily blow my box out
of the water by running tbench + kbuild with nohz_full active.  No more.

nohz_full doesn't work though, due to an otherwise solo task trying to
shut the tick down having just awakened ksoftirqd.. but no more kaboom.

	-Mike

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/