From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by e35.co.us.ibm.com (8.13.8/8.13.8) with ESMTP id m46JBtxf031354 for ; Tue, 6 May 2008 15:11:55 -0400 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay04.boulder.ibm.com (8.13.8/8.13.8/NCO v8.7) with ESMTP id m46JBtcN128078 for ; Tue, 6 May 2008 13:11:55 -0600 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m46JBsKV013768 for ; Tue, 6 May 2008 13:11:54 -0600 Date: Tue, 6 May 2008 12:11:53 -0700 From: "Paul E. McKenney" Subject: Re: [patch 2/2] fix SMP data race in pagetable setup vs walking Message-ID: <20080506191153.GB8369@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20080505112021.GC5018@wotan.suse.de> <20080505121240.GD5018@wotan.suse.de> <20080506095138.GE10141@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: Nick Piggin , Hugh Dickins , linux-arch@vger.kernel.org, Linux Memory Management List List-ID: On Tue, May 06, 2008 at 07:53:23AM -0700, Linus Torvalds wrote: > > > On Tue, 6 May 2008, Nick Piggin wrote: > > > > Right. As the comment says, the x86 stuff is kind of a "reference" > > implementation, although if you prefer it isn't there, then I I can > > easily just make it alpha only. > > If there really was a point in teaching people about > "read_barrier_depends()", I'd agree that it's probably good to have it as > a reference in the x86 implementation. > > But since alpha is the only one that needs it, and is likely to remain so, > it's not like we ever want to copy that code to anything else, and it > really is better to make it alpha-only if the code is so much uglier. > > Maybe just a comment? > > As to the ACCESS_ONCE() thing, thinking about it some more, I doubt it > really matters. We're never going to change pgd anyway, so who cares if we > access it once or a hundred times? If we are never going to change mm->pgd, then why do we need the smp_read_barrier_depends()? Is this handling the initialization case or some such? Thanx, Paul -- 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