Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752238AbaKJK1c (ORCPT ); Mon, 10 Nov 2014 05:27:32 -0500 Received: from mail-wg0-f50.google.com ([74.125.82.50]:62155 "EHLO mail-wg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751725AbaKJK1b (ORCPT ); Mon, 10 Nov 2014 05:27:31 -0500 Date: Mon, 10 Nov 2014 11:27:25 +0100 From: Ingo Molnar To: Arnaldo Carvalho de Melo Cc: Peter Zijlstra , Vince Weaver , Stephane Eranian , Jiri Olsa , Andy Lutomirski , Thomas Gleixner , LKML Subject: Re: [RFD] perf syscall error handling Message-ID: <20141110102725.GA19309@gmail.com> References: <20141030222814.GF15602@worktop.programming.kicks-ass.net> <20141031072109.GD12706@worktop.programming.kicks-ass.net> <20141031092713.GA23124@gmail.com> <20141031122824.GZ12020@console-pimps.org> <20141103162548.GB18464@kernel.org> <20141103165019.GY10501@worktop.programming.kicks-ass.net> <20141103170059.GC18464@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141103170059.GC18464@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Arnaldo Carvalho de Melo wrote: > Em Mon, Nov 03, 2014 at 05:50:19PM +0100, Peter Zijlstra escreveu: > > On Mon, Nov 03, 2014 at 02:25:48PM -0200, Arnaldo Carvalho de Melo wrote: > > > > The way that peterz suggested, i.e. returning information about which > > > perf_event_attr and which of the parameters was invalid/had issues could > > > help with fallbacking/capability querying, i.e. tooling may want to use > > > some features if available automagically, fallbacking to something else > > > when that fails. > > > > We already do that to some degree in various cases, but for some if the > > > only way that becomes available to disambiguate some EINVAL return is a > > > string, code will start having strcmps :-\ > > > OK, so how about we do both, the offset+mask for the tools > > and the string for the humans? > > Yeah, tooling tries to provide the best it can with the > offset+mask, and if doesn't manage to do anything smart with > it, just show the string and hope that helps the user to figure > out what is happening. Almost: tooling should generally always consider the string as well, for the (not so uncommon) case where there can be multiple problems with the same field. Really, I think the string will give the most bang for the buck, because it's really simple and straightforward on the kernel side (so that we have a good chance of achieving full coverage relatively quickly), and later on we could still complicate it all with offset+mask if there's really a need. So lets start with an error string... Thanks, Ingo -- 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/