From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 1833B6B005A for ; Wed, 17 Jun 2009 03:50:00 -0400 (EDT) Date: Wed, 17 Jun 2009 09:51:31 +0200 From: Nick Piggin Subject: Re: [PATCH 1/5] HWPOISON: define VM_FAULT_HWPOISON to 0 when feature is disabled Message-ID: <20090617075131.GC26664@wotan.suse.de> References: <20090611142239.192891591@intel.com> <20090611144430.414445947@intel.com> <20090612112258.GA14123@elte.hu> <20090612125741.GA6140@localhost> <20090612131754.GA32105@elte.hu> <20090612153501.GA5737@elte.hu> <20090615065232.GC18390@wotan.suse.de> <20090616202726.GB31443@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090616202726.GB31443@sgi.com> Sender: owner-linux-mm@kvack.org To: Russ Anderson Cc: Ingo Molnar , Linus Torvalds , Wu Fengguang , Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Andrew Morton , LKML , Hugh Dickins , Andi Kleen , "riel@redhat.com" , "chris.mason@oracle.com" , "linux-mm@kvack.org" List-ID: On Tue, Jun 16, 2009 at 03:27:26PM -0500, Russ Anderson wrote: > On Mon, Jun 15, 2009 at 08:52:32AM +0200, Nick Piggin wrote: > > On Fri, Jun 12, 2009 at 05:35:01PM +0200, Ingo Molnar wrote: > > > * Linus Torvalds wrote: > > > > On Fri, 12 Jun 2009, Ingo Molnar wrote: > > > > > > > > > > This seems like trying to handle a failure mode that cannot be > > > > > and shouldnt be 'handled' really. If there's an 'already > > > > > corrupted' page then the box should go down hard and fast, and > > > > > we should not risk _even more user data corruption_ by trying to > > > > > 'continue' in the hope of having hit some 'harmless' user > > > > > process that can be killed ... > > > > > > > > No, the box should _not_ go down hard-and-fast. That's the last > > > > thing we should *ever* do. > > > > > > > > We need to log it. Often at a user level (ie we want to make sure > > > > it actually hits syslog, possibly goes out the network, maybe pops > > > > up a window, whatever). > > > > > > > > Shutting down the machine is the last thing we ever want to do. > > > > > > > > The whole "let's panic" mentality is a disease. > > > > > > No doubt about that - and i'm removing BUG_ON()s and panic()s > > > wherever i can and havent added a single new one myself in the past > > > 5 years or so, its a disease. > > > > In HA failover systems you often do want to panic ASAP (after logging > > to serial cosole I guess) if anything like this happens so the system > > can be rebooted with minimal chance of data corruption spreading. > > The whole point of hardware data poisoning is to avoid having to > panic the system due to the potential of undetected data corruption, > because the corrupt data is always marked bad. This has worked > well on ia64 where applications that encounter bad data are killed > and the memory poisoned and not reallocated, avoiding a system panic. > > This has been used at customer sites for a few years. The type > customers that really check their data. It is nice to see > the hardware poison feature moving to the x86 "mainstream". So long as you can get an MCE and panic if the corrupt data actually gets consumed anywhere, then yes a "corrupt data detected but not consumed" exception would not require a panic. I don't know enough about the arch details to know what kinds of exceptions happen when. -- 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