From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 055208D0040 for ; Thu, 24 Mar 2011 14:06:11 -0400 (EDT) Received: by yxt33 with SMTP id 33so154114yxt.14 for ; Thu, 24 Mar 2011 11:06:10 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <20110324142146.GA11682@elte.hu> <20110324172653.GA28507@elte.hu> Date: Thu, 24 Mar 2011 20:06:10 +0200 Message-ID: Subject: Re: [GIT PULL] SLAB changes for v2.6.39-rc1 From: Pekka Enberg Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Ingo Molnar , torvalds@linux-foundation.org, akpm@linux-foundation.org, tj@kernel.org, npiggin@kernel.dk, rientjes@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Thu, Mar 24, 2011 at 8:01 PM, Christoph Lameter wrote: > On Thu, 24 Mar 2011, Pekka Enberg wrote: > >> On Thu, Mar 24, 2011 at 7:43 PM, Christoph Lameter wrote: >> > The bug should only trigger on old AMD64 boxes that do not support >> > cmpxchg16b. >> >> Yup. Ingo is it possible to see /proc/cpuinfo of one of the affected >> boxes? I'll try your config but I'm pretty sure the problem doesn't >> trigger here. Like I said, I think the problem is that alternative >> instructions are not patched early enough for cmpxchg16b emulation to >> work for kmem_cache_init(). I tried my check_bugs() patch but it hangs >> during boot. I'll see if I can cook up a patch that does >> alternative_instructions() before kmem_cache_init() because I think >> those *should* be available during boot too. > > I forced the fallback to the _emu function to occur but could not trigger > the bug in kvm. That's not the problem. I'm sure the fallback is just fine. What I'm saying is that the fallback is *not patched* to kernel text on Ingo's machines because alternative_instructions() happens late in the boot! So the problem is that on Ingo's boxes (that presumably have old AMD CPUs) we execute cmpxchg16b, not the fallback code. Pekka -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org