Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758061AbcDHOeh (ORCPT ); Fri, 8 Apr 2016 10:34:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57702 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753626AbcDHOef (ORCPT ); Fri, 8 Apr 2016 10:34:35 -0400 Date: Fri, 8 Apr 2016 09:34:33 -0500 From: Josh Poimboeuf To: Petr Mladek Cc: Jiri Kosina , Jessica Yu , Miroslav Benes , linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, Vojtech Pavlik Subject: Re: [RFC PATCH v1.9 05/14] sched: horrible way to detect whether a task has been preempted Message-ID: <20160408143433.rlwlru7olr2cs2ll@treble.redhat.com> References: <24db5a6ae5b63dfcd2096a12d18e1399a351348e.1458933243.git.jpoimboe@redhat.com> <20160406130619.GA5218@pathway.suse.cz> <20160406163356.hba6jzkloaukknn4@treble.redhat.com> <20160407094700.GA27670@pathway.suse.cz> <20160407143403.6f7wvjvh2r43e4la@treble.redhat.com> <20160408080710.GF5218@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20160408080710.GF5218@pathway.suse.cz> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1124 Lines: 28 On Fri, Apr 08, 2016 at 10:07:10AM +0200, Petr Mladek wrote: > On Thu 2016-04-07 09:34:03, Josh Poimboeuf wrote: > > On Thu, Apr 07, 2016 at 11:47:00AM +0200, Petr Mladek wrote: > > > On Wed 2016-04-06 11:33:56, Josh Poimboeuf wrote: > > > > On Wed, Apr 06, 2016 at 03:06:19PM +0200, Petr Mladek wrote: > > > We could even move this check into the livepatch code but then > > > print_context_stack_reliable() will not always give reliable results. > > > > Why would moving the check to the livepatch code affect the reliability > > of print_context_stack_reliable()? > > print_context_stack_reliable() is a generic function that might > eventualy be used also outside livepatch code. If there is > preempt_schedule_irq() on the stack, it means that the rest > of the stack might be unreliable and it should be detected > by the function itself. Ah, I see now. I actually thought you meant something else (moving in_preempt_schedule_irq() itself to livepatch code, but still calling it from print_context_stack_reliable()). > Let's forget the idea of moving the check into the livepatch > code :-) Agreed :-) -- Josh