From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id DED1C6007B8 for ; Mon, 3 May 2010 13:19:09 -0400 (EDT) Date: Mon, 3 May 2010 19:18:37 +0200 From: Andrea Arcangeli Subject: Re: [PATCH 1/2] mm: Take all anon_vma locks in anon_vma_lock Message-ID: <20100503171837.GG19891@random.random> References: <20100503121743.653e5ecc@annuminas.surriel.com> <20100503121847.7997d280@annuminas.surriel.com> <1272905712.1642.150.camel@laptop> <20100503170230.GF19891@random.random> <1272906679.1642.152.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1272906679.1642.152.camel@laptop> Sender: owner-linux-mm@kvack.org To: Peter Zijlstra Cc: Rik van Riel , akpm@linux-foundation.org, torvalds@linux-foundation.org, Mel Gorman , Linux-MM , LKML , Minchan Kim , KAMEZAWA Hiroyuki , Christoph Lameter List-ID: On Mon, May 03, 2010 at 07:11:19PM +0200, Peter Zijlstra wrote: > On Mon, 2010-05-03 at 19:02 +0200, Andrea Arcangeli wrote: > > On Mon, May 03, 2010 at 06:55:12PM +0200, Peter Zijlstra wrote: > > > This does leave me worrying about concurrent faults poking at > > > vma->vm_end without synchronization. > > > > I didn't check this patch in detail yet. I agree it can be removed and > > I think it can be safely replaced with the page_table_lock. > > Sure, it could probably be replaced with the ptl, but a single > anon_vma->lock would I think be better since there's more of them. ptl not enough, or it'd break if stack grows fast more than the size of one pmd, page_table_lock enough instead. Keeping anon_vma lock is sure fine with me ;), I was informally asked if it was a must have, and I couldn't foresee any problem in _replacing_ it (not removing) with page_table_lock (which I hope I mentioned in my answer ;). But I never had an interest to remove it, just I couldn't find any good reason to keep it either other than "paranoid just in case", which is good enough justification to me ;) considering these archs are uncommon and by definition gets less testing. -- 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