Return-Path: Received: from ftp.linux-mips.org ([194.74.144.162]:47133 "EHLO ftp.linux-mips.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751141AbXKUNuc (ORCPT ); Wed, 21 Nov 2007 08:50:32 -0500 Received: from localhost.localdomain ([127.0.0.1]:44454 "EHLO dl5rb.ham-radio-op.net") by ftp.linux-mips.org with ESMTP id S20043662AbXKUNub (ORCPT ); Wed, 21 Nov 2007 13:50:31 +0000 Date: Wed, 21 Nov 2007 13:50:16 +0000 From: Ralf Baechle Subject: Re: [rfc] io memory barriers, and getting rid of mmiowb Message-ID: <20071121135016.GB15318@linux-mips.org> References: <20071120160220.GA22196@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071120160220.GA22196@wotan.suse.de> Sender: linux-arch-owner@vger.kernel.org To: Nick Piggin , dhowells@redhat.com Cc: linux-arch@vger.kernel.org, Linus Torvalds , Benjamin Herrenschmidt List-ID: On Tue, Nov 20, 2007 at 05:02:20PM +0100, Nick Piggin wrote: > + TYPE FULL CACHEABLE (SMP CONDITIONAL) IO > + ========= ======================= =========================== ============ > + GENERAL mb() smp_mb() io_mb() > + WRITE wmb() smp_wmb() io_wmb() > + READ rmb() smp_rmb() io_rmb() > + DATA DEP. read_barrier_depends() smp_read_barrier_depends() A while ago I went through the kernel looking at the uses mb(), wmb() and rmb() and found that every use was either fishy or should have been a smp_mb(), smp_wmb() or wmp_rmb(). Which leads me to the question if there is any need for the non-smp_ variants left or can we just bury them? Ralf