Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764850AbZLQOp6 (ORCPT ); Thu, 17 Dec 2009 09:45:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758746AbZLQOpz (ORCPT ); Thu, 17 Dec 2009 09:45:55 -0500 Received: from e3.ny.us.ibm.com ([32.97.182.143]:48166 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758294AbZLQOpy (ORCPT ); Thu, 17 Dec 2009 09:45:54 -0500 Date: Thu, 17 Dec 2009 06:45:51 -0800 From: "Paul E. McKenney" To: Andi Kleen Cc: Peter Zijlstra , KAMEZAWA Hiroyuki , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , cl@linux-foundation.org, "akpm@linux-foundation.org" , "mingo@elte.hu" , minchan.kim@gmail.com Subject: Re: [mm][RFC][PATCH 0/11] mm accessor updates. Message-ID: <20091217144551.GA6819@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20091216120011.3eecfe79.kamezawa.hiroyu@jp.fujitsu.com> <20091216101107.GA15031@basil.fritz.box> <20091216191312.f4655dac.kamezawa.hiroyu@jp.fujitsu.com> <20091216102806.GC15031@basil.fritz.box> <20091216193109.778b881b.kamezawa.hiroyu@jp.fujitsu.com> <1261004224.21028.500.camel@laptop> <20091217084046.GA9804@basil.fritz.box> <1261039534.27920.67.camel@laptop> <20091217085430.GG9804@basil.fritz.box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091217085430.GG9804@basil.fritz.box> 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 Content-Length: 1501 Lines: 39 On Thu, Dec 17, 2009 at 09:54:30AM +0100, Andi Kleen wrote: > On Thu, Dec 17, 2009 at 09:45:34AM +0100, Peter Zijlstra wrote: > > On Thu, 2009-12-17 at 09:40 +0100, Andi Kleen wrote: > > > On Wed, Dec 16, 2009 at 11:57:04PM +0100, Peter Zijlstra wrote: > > > > On Wed, 2009-12-16 at 19:31 +0900, KAMEZAWA Hiroyuki wrote: > > > > > > > > > The problem of range locking is more than mmap_sem, anyway. I don't think > > > > > it's possible easily. > > > > > > > > We already have a natural range lock in the form of the split pte lock. > > > > > > > > If we make the vma lookup speculative using RCU, we can use the pte lock > > > > > > One problem is here that mmap_sem currently contains sleeps > > > and RCU doesn't work for blocking operations until a custom > > > quiescent period is defined. > > > > Right, so one thing we could do is always have preemptible rcu present > > in another RCU flavour, like > > > > rcu_read_lock_sleep() > > rcu_read_unlock_sleep() > > call_rcu_sleep() > > > > or whatever name that would be, and have PREEMPT_RCU=y only flip the > > regular rcu implementation between the sched/sleep one. > > That could work yes. OK, I have to ask... Why not just use the already-existing SRCU in this case? Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/