From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [patch] i386: avoid expensive ppro ordering workaround for default 686 kernels From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org In-Reply-To: <20080103142330.111d4067@lxorguk.ukuu.org.uk> References: <20071218012632.GA23110@wotan.suse.de> <20071222005737.2675c33b.akpm@linux-foundation.org> <20071223055730.GA29288@wotan.suse.de> <20071222223234.7f0fbd8a.akpm@linux-foundation.org> <20071223071529.GC29288@wotan.suse.de> <20080101234133.4a744329@the-village.bc.nu> <20080102110225.GA16154@wotan.suse.de> <20080102134433.6ca82011@the-village.bc.nu> <20080103041708.GB26487@wotan.suse.de> <20080103142330.111d4067@lxorguk.ukuu.org.uk> Content-Type: text/plain Date: Fri, 04 Jan 2008 07:20:43 +1100 Message-Id: <1199391643.7291.15.camel@pasglop> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Alan Cox Cc: Nick Piggin , Linus Torvalds , Andrew Morton , Hugh Dickins , Linux Memory Management List List-ID: On Thu, 2008-01-03 at 14:23 +0000, Alan Cox wrote: > > Hmm, I don't understand what you mean. Obviously other busmasters aren't > > participating in any locking or smp_*mb() ordering protocols. > > The unlock paths are visible to busmasters > > write to DMA buffer > unlock > can turn into > > unlock > write to DMA buffer > > Whether that actually matters in any code we have I don't know. It matters with writes to MMIO at least, I don't know if your PPro bug can cause that to be re-ordered tho. Ben. -- 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