From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id E41146B005D for ; Wed, 17 Jun 2009 04:04:04 -0400 (EDT) Date: Wed, 17 Jun 2009 10:04:04 +0200 From: Nick Piggin Subject: Re: [RFC][PATCH] HWPOISON: only early kill processes who installed SIGBUS handler Message-ID: <20090617080404.GB31192@wotan.suse.de> References: <20090615024520.786814520@intel.com> <4A35BD7A.9070208@linux.vnet.ibm.com> <20090615042753.GA20788@localhost> <20090615064447.GA18390@wotan.suse.de> <20090615070914.GC31969@one.firstfloor.org> <20090615071907.GA8665@wotan.suse.de> <20090615121001.GA10944@localhost> <20090615122528.GA13256@wotan.suse.de> <20090615142225.GA11167@localhost> <20090617063702.GA20922@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090617063702.GA20922@localhost> Sender: owner-linux-mm@kvack.org To: Wu Fengguang Cc: Andi Kleen , Balbir Singh , Andrew Morton , LKML , Ingo Molnar , Mel Gorman , Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Hugh Dickins , "riel@redhat.com" , "chris.mason@oracle.com" , "linux-mm@kvack.org" List-ID: On Wed, Jun 17, 2009 at 02:37:02PM +0800, Wu Fengguang wrote: > On Mon, Jun 15, 2009 at 10:22:25PM +0800, Wu Fengguang wrote: > > On Mon, Jun 15, 2009 at 08:25:28PM +0800, Nick Piggin wrote: > > > On Mon, Jun 15, 2009 at 08:10:01PM +0800, Wu Fengguang wrote: > > > > On Mon, Jun 15, 2009 at 03:19:07PM +0800, Nick Piggin wrote: > > > > > > For KVM you need early kill, for the others it remains to be seen. > > > > > > > > > > Right. It's almost like you need to do a per-process thing, and > > > > > those that can handle things (such as the new SIGBUS or the new > > > > > EIO) could get those, and others could be killed. > > > > > > > > To send early SIGBUS kills to processes who has called > > > > sigaction(SIGBUS, ...)? KVM will sure do that. For other apps we > > > > don't mind they can understand that signal at all. > > > > > > For apps that hook into SIGBUS for some other means and > > > > Yes I was referring to the sigaction(SIGBUS) apps, others will > > be late killed anyway. > > > > > do not understand the new type of SIGBUS signal? What about > > > those? > > > > We introduced two new SIGBUS codes: > > BUS_MCEERR_AO=5 for early kill > > BUS_MCEERR_AR=4 for late kill > > I'd assume a legacy application will handle them in the same way (both > > are unexpected code to the application). > > > > We don't care whether the application can be killed by BUS_MCEERR_AO > > or BUS_MCEERR_AR depending on its SIGBUS handler implementation. > > But (in the rare case) if the handler > > - refused to die on BUS_MCEERR_AR, it may create a busy loop and > > flooding of SIGBUS signals, which is a bug of the application. > > BUS_MCEERR_AO is one time and won't lead to busy loops. > > - does something that hurts itself (ie. data safety) on BUS_MCEERR_AO, > > it may well hurt the same way on BUS_MCEERR_AR. The latter one is > > unavoidable, so the application must be fixed anyway. > > This patch materializes the automatically early kill idea. > It aims to remove the vm.memory_failure_ealy_kill sysctl parameter. > > This is mainly a policy change, please comment. Well then you can still early-kill random apps that did not want it, and you may still cause problems if its sigbus handler does something nontrivial. Can you use a prctl or something so it can expclitly register interest in this? -- 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