Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753712AbYJRC6R (ORCPT ); Fri, 17 Oct 2008 22:58:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751786AbYJRC6A (ORCPT ); Fri, 17 Oct 2008 22:58:00 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:54516 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751780AbYJRC57 (ORCPT ); Fri, 17 Oct 2008 22:57:59 -0400 Date: Fri, 17 Oct 2008 19:57:27 -0700 (PDT) From: Linus Torvalds To: Paul Mackerras cc: Nick Piggin , Hugh Dickins , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org Subject: Re: [patch] mm: fix anon_vma races In-Reply-To: <18681.20241.347889.843669@cargo.ozlabs.ibm.com> Message-ID: References: <20081016041033.GB10371@wotan.suse.de> <20081018015323.GA11149@wotan.suse.de> <18681.20241.347889.843669@cargo.ozlabs.ibm.com> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1185 Lines: 30 On Sat, 18 Oct 2008, Paul Mackerras wrote: > > Not sure what you mean by causal consistency, but I assume it's the > same as saying that barriers give cumulative ordering, as described on > page 413 of the Power Architecture V2.05 document at: I'm pretty sure that everybody but alpha is ok. And alpha needs the smp_read_barrier_depends() not because it doesn't really support causality, but because each CPU internally doesn't guarantee that they handle the cache invalidates in-order without a barrier. So without the smp_read_barrier_depends(), alpha will actually have the proper causal relationships (cachelines will move to exclusive state on CPU0 in the right order and others will see the causality), but because CPU2 may see the stale data from not even having invalidated the "anon_vma.initialized" because the cache invalidation queue hadn't been flushed in order. Alpha is insane. And the odd man out. Linus -- 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/