From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755260Ab1LAWPE (ORCPT ); Thu, 1 Dec 2011 17:15:04 -0500 Received: from mail.openrapids.net ([64.15.138.104]:41111 "EHLO blackscsi.openrapids.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754543Ab1LAWPC (ORCPT ); Thu, 1 Dec 2011 17:15:02 -0500 Date: Thu, 1 Dec 2011 17:15:00 -0500 From: Mathieu Desnoyers To: Peter Zijlstra Cc: Greg KH , devel@driverdev.osuosl.org, lttng-dev@lists.lttng.org, Ingo Molnar , linux-kernel@vger.kernel.org, Darren Hart Subject: Re: [PATCH 09/11] sched: export task_prio to GPL modules Message-ID: <20111201221500.GC10552@Krystal> References: <1322775683-8741-1-git-send-email-mathieu.desnoyers@efficios.com> <1322775683-8741-10-git-send-email-mathieu.desnoyers@efficios.com> <1322776568.4699.52.camel@twins> <20111201220445.GA10552@Krystal> <1322777407.4699.59.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1322777407.4699.59.camel@twins> X-Editor: vi X-Info: http://www.efficios.com X-Operating-System: Linux/2.6.26-2-686 (i686) X-Uptime: 17:10:59 up 373 days, 3:14, 6 users, load average: 0.09, 0.12, 0.09 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra (peterz@infradead.org) wrote: > On Thu, 2011-12-01 at 17:04 -0500, Mathieu Desnoyers wrote: > > * Peter Zijlstra (peterz@infradead.org) wrote: > > > On Thu, 2011-12-01 at 16:41 -0500, Mathieu Desnoyers wrote: > > > > LTTng needs this symbol to prepend the current task dynamic priority > > > > value to events (optional context information). > > > > > > I absolutely detest exporting such stuff. It propagates the idea that > > > task prio actually means something. Also, modules really shouldn't care. > > > > People debugging their SCHED_FIFO/SCHED_RR applications, as well as > > users of priority-inheritance futexes, may happen to find this > > information extremely useful. > > > > Just saying... > > Right until the moment we go do deadlines.. Anyway, it still doesn't > make sense, your sched_switch() tracepoint handler gets this > information, why do you need this export at all? If you don't want to trace sched_switch, but just conveniently prepend this information to all your events, then lttng lets you dynamically target this extra bit of information. Note that it's not a mandatory event field: I call those "context" fields that the tracer prepends to events, as requested by the user. Thanks, Mathieu -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com