From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sun, 23 Dec 2007 01:28:20 -0800 From: Andrew Morton Subject: Re: [patch] mm: fix PageUptodate memory ordering bug Message-Id: <20071223012820.3a0e4db3.akpm@linux-foundation.org> In-Reply-To: <20071223091405.GA15631@wotan.suse.de> 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> <20071222232932.590e2b6c.akpm@linux-foundation.org> <20071223091405.GA15631@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Hugh Dickins , Linux Memory Management List , Benjamin Herrenschmidt , Linus Torvalds , Andi Kleen , Ingo Molnar , Alan Cox List-ID: On Sun, 23 Dec 2007 10:14:05 +0100 Nick Piggin wrote: > config X86_PPRO_FENCE > - bool > + bool "PentiumPro memory ordering errata workaround" > depends on M686 || M586MMX || M586TSC || M586 || M486 || M386 || MGEODEGX1 > - default y > + default n > + help > + Old PentiumPro multiprocessor systems had errata that could cause memory > + operations to violate the x86 ordering standard in rare cases. Enabling this > + option will attempt to work around some (but not all) occurances of > + this problem, at the cost of much heavier spinlock and memory barrier > + operations. > + > + If unsure, say n here. Even distro kernels should think twice before enabling > + this: there are few systems, and an unlikely bug. > I think if we're going to do this then we should add a runtime check for the offending CPU then do panic("your kernel config ain't right"). -- 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