Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755517AbbBLL4g (ORCPT ); Thu, 12 Feb 2015 06:56:36 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:55081 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755220AbbBLL4f (ORCPT ); Thu, 12 Feb 2015 06:56:35 -0500 Date: Thu, 12 Feb 2015 12:56:28 +0100 From: Peter Zijlstra To: Josh Poimboeuf Cc: Ingo Molnar , Masami Hiramatsu , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Seth Jennings , Jiri Kosina , Vojtech Pavlik Subject: Re: [RFC PATCH 6/9] livepatch: create per-task consistency model Message-ID: <20150212115628.GL2896@worktop.programming.kicks-ass.net> References: <2c3d1e685dae5cccc2dfdb1b24c241b2f1c89348.1423499826.git.jpoimboe@redhat.com> <20150212032121.GA18578@treble.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150212032121.GA18578@treble.redhat.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1414 Lines: 34 On Wed, Feb 11, 2015 at 09:21:21PM -0600, Josh Poimboeuf wrote: > Ingo, Peter, > > Would you have any objections to making task_rq_lock/unlock() non-static > (or moving them to kernel/sched/sched.h) so they can be called by the > livepatch code? Basically yes. I really don't want to expose that. And kernel/sched/sched.h is very much not intended for use outside of kernel/sched/ so even that is a no go. > To provide some background, I'm looking for a way to temporarily prevent > a sleeping task from running while its stack is examined, to decide > whether it can be safely switched to the new patching "universe". For > more details see klp_transition_task() in the patch below. > > Using task_rq_lock() is the most straightforward way I could find to > achieve that. Its not at all clear how all this would work to me. And I'm not motivated enough to go try and reverse engineer your patch; IMO livepatching is utter fail. If your infrastructure relies on the uptime of a single machine you've lost already. FWIW, the barriers in klp_update_task_universe() and klp_set_universe_goal() look like complete crack, and their comments are seriously deficient. -- 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/