Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755918AbbBLO1I (ORCPT ); Thu, 12 Feb 2015 09:27:08 -0500 Received: from cantor2.suse.de ([195.135.220.15]:41078 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752766AbbBLO1F (ORCPT ); Thu, 12 Feb 2015 09:27:05 -0500 Date: Thu, 12 Feb 2015 15:27:03 +0100 (CET) From: Jiri Kosina To: Josh Poimboeuf cc: Peter Zijlstra , Ingo Molnar , Masami Hiramatsu , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Seth Jennings , Vojtech Pavlik Subject: Re: [RFC PATCH 6/9] livepatch: create per-task consistency model In-Reply-To: <20150212142035.GD18578@treble.redhat.com> Message-ID: References: <2c3d1e685dae5cccc2dfdb1b24c241b2f1c89348.1423499826.git.jpoimboe@redhat.com> <20150212032121.GA18578@treble.redhat.com> <20150212115628.GL2896@worktop.programming.kicks-ass.net> <20150212125149.GB18578@treble.redhat.com> <20150212130817.GV23123@twins.programming.kicks-ass.net> <20150212142035.GD18578@treble.redhat.com> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1223 Lines: 37 On Thu, 12 Feb 2015, Josh Poimboeuf wrote: > > and you have a livepatch patching foo() and changing its return value > > semantics. Then freezer doesn't really help. > > Don't we have the same issue with livepatch? For example: > > while (some_condition) { > ret = foo(); > ... > schedule(); <-- switch to the new universe while it's sleeps > ... > // use ret in an unexpected way > } Well if ret is changing semantics, the livepatch will also have to patch the calling function (so that it handles new semantics properly), and therefore by looking at the stacks you would see that fact and wouldn't migrate the scheduled-out task to the new universe. > I think it's not really a problem, just something the patch author needs > to be aware of regardless. Exactly; that's just up to the patch author to undersntad what the semantical aspects of the patch he is writing are, and make appropriate consistency model choice. Thanks, -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/