From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 6BDCD6B0047 for ; Wed, 16 Dec 2009 18:02:23 -0500 (EST) Subject: Re: [mm][RFC][PATCH 0/11] mm accessor updates. From: Peter Zijlstra In-Reply-To: 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> <20091216104951.GD15031@basil.fritz.box> <20091216201218.42ff7f05.kamezawa.hiroyu@jp.fujitsu.com> <20091216113158.GE15031@basil.fritz.box> Content-Type: text/plain; charset="UTF-8" Date: Thu, 17 Dec 2009 00:01:55 +0100 Message-ID: <1261004515.21028.510.camel@laptop> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: Andi Kleen , KAMEZAWA Hiroyuki , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "mingo@elte.hu" , minchan.kim@gmail.com List-ID: On Wed, 2009-12-16 at 10:27 -0600, Christoph Lameter wrote: > On Wed, 16 Dec 2009, Andi Kleen wrote: > > > > Do you have alternative recommendation rather than wrapping all accesses by > > > special functions ? > > > > Work out what changes need to be done for ranged mmap locks and do them all > > in one pass. > > Locking ranges is already possible through the split ptlock and > could be enhanced through placing locks in the vma structures. > > That does nothing solve the basic locking issues of mmap_sem. We need > Kame-sans abstraction layer. A vma based lock or a ptlock still needs to > ensure that the mm struct does not vanish while the lock is held. It should, you shouldn't be able to remove a mm while there's still vma's around, and you shouldn't be able to remove a vma when there's still pagetables around. And if you rcu-free all of them you're stable enough for lots of speculative behaviour. No need to retain mmap_sem for any of that. As for per-vma locks, those are pretty much useless too, there's plenty applications doing lots of work on a few very large vmas. -- 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/ . Don't email: email@kvack.org