Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754671AbcDNIud (ORCPT ); Thu, 14 Apr 2016 04:50:33 -0400 Received: from mx2.suse.de ([195.135.220.15]:33153 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754652AbcDNIub (ORCPT ); Thu, 14 Apr 2016 04:50:31 -0400 Date: Thu, 14 Apr 2016 10:50:28 +0200 (CEST) From: Miroslav Benes To: Josh Poimboeuf cc: Jiri Kosina , Jessica Yu , linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, Vojtech Pavlik Subject: Re: [RFC PATCH v1.9 14/14] livepatch: update task universe when exiting kernel In-Reply-To: Message-ID: References: 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: 1159 Lines: 26 On Thu, 14 Apr 2016, Miroslav Benes wrote: > On Fri, 25 Mar 2016, Josh Poimboeuf wrote: > > > Update a tasks's universe when returning from a system call or user > > space interrupt, or after handling a signal. > > > > This greatly increases the chances of a patch operation succeeding. If > > a task is I/O bound, it can switch universes when returning from a > > system call. If a task is CPU bound, it can switch universes when > > returning from an interrupt. If a task is sleeping on a to-be-patched > > function, the user can send SIGSTOP and SIGCONT to force it to switch. > > > > Since the idle "swapper" tasks don't ever exit the kernel, they're > > updated from within the idle loop. > > Well, I am still not familiarized enough with Andy's recent rework of > entry stuff, but I think all of this is correct. Maybe I would add > a note to the changelog, that since TIF_KLP_NEED_UPDATE is defined 14th > bit it is also automatically included in _TIF_ALLWORK_MASKS. And I forgot to add that I would try to prepare similar thing for s390 and maybe powerpc (taking recent development there into account). That's gonna be fun :) Miroslav