linux-kernel - Re: [PATCH -tip/core/rcu 1/6] Cleanups and fixes for RCU in face of heavy CPU-hotplug stress

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: <20090821141721.GA11098@elte.hu>
Date:	Fri, 21 Aug 2009 16:17:21 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josht@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org, dvhltc@...ibm.com,
	niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, hugh.dickins@...cali.co.uk,
	benh@...nel.crashing.org
Subject: Re: [PATCH -tip/core/rcu 1/6] Cleanups and fixes for RCU in face
	of heavy CPU-hotplug stress


* Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> wrote:

> I would not trust this architecture for synchronization tests. 
> There has been reports of a hardware bug affecting the cmpxchg 
> instruction in the field. The load fence normally implied by the 
> semantic seems to be missing. AFAIK, AMD never acknowledged the 
> problem.

If cmpxchg was broken i'd be having far worse problems and very 
widely so.

FYI, this was the same box i prototyped/developed -rt on, which uses 
cmpxchg for _everything_.

That's not a proof of course (it's near impossible to prove the lack 
of a bug), but it's sure a strong indicator and you'll need to 
provide far more proof of misbehavior before i discount a bona fide 
regression on this box.

	Ingo
--
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/