From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754424AbYGaHOW (ORCPT ); Thu, 31 Jul 2008 03:14:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752910AbYGaHOO (ORCPT ); Thu, 31 Jul 2008 03:14:14 -0400 Received: from smtp112.mail.mud.yahoo.com ([209.191.84.65]:36219 "HELO smtp112.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752423AbYGaHON (ORCPT ); Thu, 31 Jul 2008 03:14:13 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:X-Yahoo-Newman-Property:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Content-Disposition:Message-Id; b=FjlJS3oAwoovbd9vN65L+VmrGfpC2CpXvQ+YsNPJZ2McqJnwatYr7lnNXZ0FjACz5txzajfkegSthnXs+vNkf2gJkU35zn9ZTzrMNcSXarNpIBs02xGiHOIwNJyPz/8GDPTavmUWbBfGVYOPVMRXkLq0AjU/Qzpe7d1DZSke0Yo= ; X-YMail-OSG: Ig.H_KQVM1mPLae8N151oD1fvxi7w9l3inAJz21cm3813B.yg1S2sH2F3ub9n4T4H1GMoHR1.Ime.vnYXDaD_iFMBSD2ZJ41pf359j3EEcRzwSjoJeklNXdwQrDlbFzOC6s- X-Yahoo-Newman-Property: ymail-3 From: Nick Piggin To: Robin Holt Subject: Re: GRU driver feedback Date: Thu, 31 Jul 2008 17:14:04 +1000 User-Agent: KMail/1.9.5 Cc: "Torvalds, Linus" , Jack Steiner , Nick Piggin , Andrew Morton , Linux Memory Management List , Linux Kernel Mailing List References: <20080723141229.GB13247@wotan.suse.de> <20080729185315.GA14260@sgi.com> <200807301550.34500.nickpiggin@yahoo.com.au> In-Reply-To: <200807301550.34500.nickpiggin@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200807311714.05252.nickpiggin@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 30 July 2008 15:50, Nick Piggin wrote: > On Wednesday 30 July 2008 04:53, Robin Holt wrote: > > In the case where unmap_region is clearing page tables, the caller to > > unmap_region is expected to be holding the mmap_sem writably. Jacks > > fault handler will immediately return when it fails on the > > down_read_trylock(). > > No, you are right of course. I had in my mind the problems faced by > lockless get_user_pages, in which case I was worried about the page table > existence, but missed the fact that you're holding mmap_sem to provide > existence (which it would, as you note, although one day we may want to > reclaim page tables or something that doesn't take mmap_sem, so a big > comment would be nice here). The other thing is... then GRU should get rid of the local_irq_disable in the atomic pte lookup. By definition it is worthless if we can be operating on an mm that is not running on current (and if I understand correctly, sn2 can avoid sending tlb flush IPIs completely sometimes?)