From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754866Ab0AEQFL (ORCPT ); Tue, 5 Jan 2010 11:05:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754763Ab0AEQFJ (ORCPT ); Tue, 5 Jan 2010 11:05:09 -0500 Received: from e3.ny.us.ibm.com ([32.97.182.143]:34077 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754648Ab0AEQFH (ORCPT ); Tue, 5 Jan 2010 11:05:07 -0500 Date: Tue, 5 Jan 2010 08:05:02 -0800 From: "Paul E. McKenney" To: Peter Zijlstra Cc: KAMEZAWA Hiroyuki , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "minchan.kim@gmail.com" , cl@linux-foundation.org, "hugh.dickins" , Nick Piggin , Ingo Molnar , Linus Torvalds Subject: Re: [RFC][PATCH 4/8] mm: RCU free vmas Message-ID: <20100105160502.GA8037@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20100104182429.833180340@chello.nl> <20100104182813.479668508@chello.nl> <20100105024336.GQ6748@linux.vnet.ibm.com> <1262680116.2400.19.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1262680116.2400.19.camel@laptop> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 05, 2010 at 09:28:36AM +0100, Peter Zijlstra wrote: > On Mon, 2010-01-04 at 18:43 -0800, Paul E. McKenney wrote: > > On Mon, Jan 04, 2010 at 07:24:33PM +0100, Peter Zijlstra wrote: > > > TODO: > > > - should be SRCU, lack of call_srcu() > > > > > > In order to allow speculative vma lookups, RCU free the struct > > > vm_area_struct. > > > > > > We use two means of detecting a vma is still valid: > > > - firstly, we set RB_CLEAR_NODE once we remove a vma from the tree. > > > - secondly, we check the vma sequence number. > > > > > > These two things combined will guarantee that 1) the vma is still > > > present and two, it still covers the same range from when we looked it > > > up. > > > > OK, I think I see what you are up to here. I could get you a very crude > > throw-away call_srcu() fairly quickly. I don't yet have a good estimate > > of how long it will take me to merge SRCU into the treercu infrastructure, > > but am getting there. > > > > So, which release are you thinking in terms of? > > I'm not thinking any release yet, its very early and as Linus has > pointed out, I seem to have forgotten a rather big piece of the > picture :/ > > So I need to try and fix this glaring hole before we can continue. OK, then I will think in terms of merging SRCU into treercu before providing any sort of call_srcu(). Thanx, Paul