Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760895AbaJaHVV (ORCPT ); Fri, 31 Oct 2014 03:21:21 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:55850 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756099AbaJaHVU (ORCPT ); Fri, 31 Oct 2014 03:21:20 -0400 Date: Fri, 31 Oct 2014 08:21:09 +0100 From: Peter Zijlstra To: Vince Weaver Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Jiri Olsa , Matt Fleming , Andy Lutomirski , Stephane Eranian , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: [RFD] perf syscall error handling Message-ID: <20141031072109.GD12706@worktop.programming.kicks-ass.net> References: <20141030222814.GF15602@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 On Thu, Oct 30, 2014 at 09:16:36PM -0400, Vince Weaver wrote: > On Thu, 30 Oct 2014, Peter Zijlstra wrote: > > > So would something simple, like an offset into the struct > > perf_event_attr pointing at the current field we're trying to process > > make sense? Maybe with negative offsets to indicate the syscall > > arguments? > > > > That would narrow down the 'WTF is wrong noaw' a lot I think. But then, > > I've not actually done a lot of userspace the last few years, so maybe > > I'm just dreaming things. > > well, as someone who spends a lot of time in userspace trying to help > people who report probems like 'perf_event_open() returns EINVAL, what's > wrong' I can say pretty much anything will be an improvement. Right, the situation is dire indeed :/ > What would really help is if we could somehow return the > filename/line-number of whatever source code file that's setting errno. > > Even if perf_event_open() told me that hey, we're getting EOPNOTSUPP due > to the precise_ip parameter (something that happened just yesterday) it's > still a lot of grepping and poking around source files to find out what's > going on. It would be much better if it just told me the issue was at > kernel/events/core.c line 995 or so, but I'm not sure how you could pass > that back to the user, and one could argue it wouldn't help much the > average user without a kernel tree lying around. Would an additional bit mask help? With that we'd be able to finger the exact flag that causes pain. -- 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/