From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 403A86B0055 for ; Sat, 26 Sep 2009 15:12:01 -0400 (EDT) Date: Sat, 26 Sep 2009 21:12:01 +0200 From: Nick Piggin Subject: Re: [RFC][PATCH] HWPOISON: remove the unsafe __set_page_locked() Message-ID: <20090926191201.GC14368@wotan.suse.de> References: <20090926031537.GA10176@localhost> <20090926114806.GA12419@localhost> <20090926150555.GM30185@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090926150555.GM30185@one.firstfloor.org> Sender: owner-linux-mm@kvack.org To: Andi Kleen Cc: Wu Fengguang , Hugh Dickins , Andrew Morton , "linux-mm@kvack.org" , LKML List-ID: On Sat, Sep 26, 2009 at 05:05:55PM +0200, Andi Kleen wrote: > > However we may well end up to accept the fact that "we just cannot do > > hwpoison 100% correct", and settle with a simple and 99% correct code. > > I would prefer to avoid any oopses, but if they are unlikely enough > and too hard to fix that's bearable. The race window here is certainly rather > small. Well, several places non-atomically modify page flags, including within preempt-enabled regions... It's nasty to introduce these oopses in the hwposion code! I'm ashamed I didn't pick up on this problem seeing as I introduced several of them. > On the other hand if you cannot detect a difference in benchmarks I see > no reason not to add the additional steps, as long as the code isn't > complicated or ugly. These changes are neither. The patch to add atomics back into the fastpaths? I don't think that's acceptable at all. A config option doesn't go far enough either because distros will have to turn it on. -- 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