linux-kernel - Re: 2.6.26-rc9-git4: Reported regressions from 2.6.25

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: <20080801210949.GJ14851@linux.vnet.ibm.com>
Date:	Fri, 1 Aug 2008 14:09:49 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Adrian Bunk <bunk@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Natalie Protasevich <protasnb@...il.com>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: 2.6.26-rc9-git4: Reported regressions from 2.6.25

On Thu, Jul 10, 2008 at 08:06:20PM +0200, Ingo Molnar wrote:
> 
> * Ingo Molnar <mingo@...e.hu> wrote:
> 
> > cool! :)
> > 
> > (hm, could anyone please resend Nick's original mail? The original one 
> > is not in my lkml folder nor on lkml.org - only the quoted one.)
> 
> ok, got the mail now now:
> 
> | | Annoyed this wasn't a crazy obscure error in the algorithm I could 
> | | fix :) [...]
> 
> Paul recently ran a formal proof against all sorts of RCU details (and 
> found and fixed a few obscure races that way that no-one ever 
> triggered), so i'd be quite surprised if we found anything in the core 
> algorithm :-)
> 
> | | [...] I spent all day debugging it and had to make a special test 
> | | case (rcutorture didn't seem to trigger it), and a big RCU state 
> | | logging infrastructure to log millions of RCU state transitions and 
> | | events. Oh well.
> 
> nice debugging!

Indeed!!!

> Acked-by: Ingo Molnar <mingo@...e.hu>
> 
> i'm wondering why rcutorture didnt trigger it. I do run !HOTPLUG + 
> RCU_PREEMPT kernels and never saw this. Nor did Paul. That aspect is 
> weird.

Turns out that my environment was silently re-enabling HOTPLUG_CPU, so I
only -thought- I was testing !CPU_HOTPLUG.  Once I forced it to really
disable HOTPLUG_CPU (by manually also specifying CONFIG_SUSPEND=n and
CONFIG_HIBERNATION=n), then rcutorture complained within 10 seconds.

Sigh!!!

						Thanx, Paul
--
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/