From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752666AbbJWOyM (ORCPT ); Fri, 23 Oct 2015 10:54:12 -0400 Received: from casper.infradead.org ([85.118.1.10]:58694 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751685AbbJWOyL (ORCPT ); Fri, 23 Oct 2015 10:54:11 -0400 Date: Fri, 23 Oct 2015 16:54:07 +0200 From: Peter Zijlstra To: Alexei Starovoitov Cc: "David S. Miller" , Ingo Molnar , 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: <20151023145407.GD17308@twins.programming.kicks-ass.net> 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/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 23, 2015 at 07:42:22AM -0700, 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. Right; and I figure changing the function signature is not done because the eBPF stuff is ABI? Unfortunate indeed.