From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757341Ab0DAQHq (ORCPT ); Thu, 1 Apr 2010 12:07:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38221 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754601Ab0DAQHk (ORCPT ); Thu, 1 Apr 2010 12:07:40 -0400 Message-ID: <4BB4C48C.5000005@redhat.com> Date: Thu, 01 Apr 2010 19:06:36 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.8) Gecko/20100301 Fedora/3.0.3-1.fc12 Thunderbird/3.0.3 MIME-Version: 1.0 To: Peter Zijlstra CC: Andrea Arcangeli , Thomas Gleixner , Rik van Riel , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Kent Overstreet , Ingo Molnar , "Paul E. McKenney" Subject: Re: [COUNTERPATCH] mm: avoid overflowing preempt_count() in mmu_take_all_locks() References: <1270117906.1653.139.camel@laptop> <4BB47FC3.1020606@redhat.com> <4BB480CC.2060503@redhat.com> <1270121264.1653.205.camel@laptop> <1270122194.1653.223.camel@laptop> <20100401154249.GQ5825@random.random> <4BB4C0F5.3070204@redhat.com> <1270137406.1598.78.camel@laptop> In-Reply-To: <1270137406.1598.78.camel@laptop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/01/2010 06:56 PM, Peter Zijlstra wrote: > On Thu, 2010-04-01 at 18:51 +0300, Avi Kivity wrote: > >> On 04/01/2010 06:42 PM, Andrea Arcangeli wrote: >> >>> On Thu, Apr 01, 2010 at 01:43:14PM +0200, Peter Zijlstra wrote: >>> >>> >>>> On Thu, 2010-04-01 at 13:27 +0200, Peter Zijlstra wrote: >>>> >>>> >>>>> I've almost got a patch done that converts those two, still need to look >>>>> where that tasklist_lock muck happens. >>>>> >>>>> >>>> OK, so the below builds and boots, only need to track down that >>>> tasklist_lock nesting, but I got to run an errand first. >>>> >>>> >>> You should have a look at my old patchset where Christoph already >>> implemented this (and not for decreasing latency but to allow >>> scheduling in mmu notifier handlers, only needed by XPMEM): >>> >>> http://www.kernel.org/pub/linux/kernel/people/andrea/patches/v2.6/2.6.26-rc7/mmu-notifier-v18/ >>> >>> The ugliest part of it (that I think you missed below) is the breakage >>> of the RCU locking in the anon-vma which requires adding refcounting >>> to it. That was the worst part of the conversion as far as I can tell. >>> >>> http://www.kernel.org/pub/linux/kernel/people/andrea/patches/v2.6/2.6.26-rc7/mmu-notifier-v18/anon-vma >>> >>> >> Can we use srcu now instead? >> > I would much rather we make call_rcu_preempt() available at all times. > I don't understand. I thought the problem was that the locks were taken inside an rcu critical section; switching to srcu would fix that. But how is call_rcu_preempt() related? Grepping a bit, what is call_rcu_preempt()? my tree doesn't have it. -- error compiling committee.c: too many arguments to function