From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752281AbbJYJVt (ORCPT ); Sun, 25 Oct 2015 05:21:49 -0400 Received: from mail-wi0-f170.google.com ([209.85.212.170]:37674 "EHLO mail-wi0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750864AbbJYJVr (ORCPT ); Sun, 25 Oct 2015 05:21:47 -0400 Date: Sun, 25 Oct 2015 10:21:43 +0100 From: Ingo Molnar To: Alexei Starovoitov Cc: Peter Zijlstra , "David S. Miller" , Wang Nan , He Kuang , Kaixu Xia , Daniel Borkmann , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 net-next] bpf: fix bpf_perf_event_read() helper Message-ID: <20151025092142.GB4380@gmail.com> References: <1445559014-4667-1-git-send-email-ast@kernel.org> <20151023120335.GZ17308@twins.programming.kicks-ass.net> <562A474E.6040401@plumgrid.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <562A474E.6040401@plumgrid.com> 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 * Alexei Starovoitov wrote: > On 10/23/15 5:03 AM, Peter Zijlstra wrote: > >So the bpf_perf_event_read() returns the count value, does this not also > >mean that returning -EINVAL here is also 'wrong'? > > > >I mean, sure an actual count value that high is unlikely, but its still > >a broken interface. > > Agree. that's not pretty interface. I wish I looked at it more carefully > when it was introduced. Now it's too late to change. So I really, really think eBPF needs to have an easy to use mechanism to phase out old ABI components and introducing new (better) ones! Then old crap can be de-emphasised and eventually removed, instead of having to live with crap forever ... Thanks, Ingo