From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 299E2C4321D for ; Fri, 24 Aug 2018 08:50:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC7CA2168B for ; Fri, 24 Aug 2018 08:50:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="OK7LFeKj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BC7CA2168B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727019AbeHXMYa (ORCPT ); Fri, 24 Aug 2018 08:24:30 -0400 Received: from merlin.infradead.org ([205.233.59.134]:38182 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726325AbeHXMYa (ORCPT ); Fri, 24 Aug 2018 08:24:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=1XZnLm2rzEGM69DymWV0T5VnodzC8AvkUFIC2UFoywc=; b=OK7LFeKjtz91nijG5MnFvoXYY 3sO5oipm46znvr84nX2FVwOCdJDvWPw1da1NgbVKR5c50ni4kVwK/BgqD8PWZx1nzoDDDDXhmciUJ OPbQtevRW/QmIz305DIPiUeMhC1TETPOHVskiqbhnQ682I8VpfXXmq6kG9UnOCHOWwfieZtYTqBpP MK5NySgY7K+o7ICitPz1iv7cdeV49/H3oe94OoFFBxHbLPtXPjz2tsMh922W8NRhJty6IRIumn6Vd lpAIBqzTiVdBhaDvq9kIvSd8tKI1uxbpm8joYZmdDBFPMn2UPVN6OP4MhBA0EjppMCzHkpjUet9n3 fPa+kJ2og==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1ft7no-0007LJ-05; Fri, 24 Aug 2018 08:50:44 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BA217202E65E0; Fri, 24 Aug 2018 10:50:42 +0200 (CEST) Date: Fri, 24 Aug 2018 10:50:42 +0200 From: Peter Zijlstra To: Vince Weaver Cc: linux-kernel@vger.kernel.org, Josh Poimboeuf , Alexander Shishkin , Andy Lutomirski , Arnaldo Carvalho de Melo , Arnaldo Carvalho de Melo , Jiri Olsa , Linus Torvalds , Stephane Eranian , Thomas Gleixner , Ingo Molnar Subject: Re: [perf] perf_event.h ABI visibility question Message-ID: <20180824085042.GL24124@hirez.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 23, 2018 at 02:25:06PM -0400, Vince Weaver wrote: > > I notice that Linux 4.18 has the following changeset which changes the > user visible perf_event.h file > > commit 6cbc304f2f360f25cc8607817239d6f4a2fd3dc5 > Author: Peter Zijlstra > Date: Thu May 10 15:48:41 2018 +0200 > > perf/x86/intel: Fix unwind errors from PEBS entries (mk-II) > > which contains > > --- a/include/uapi/linux/perf_event.h > +++ b/include/uapi/linux/perf_event.h > @@ -143,6 +143,8 @@ enum perf_event_sample_format { > PERF_SAMPLE_PHYS_ADDR = 1U << 19, > > PERF_SAMPLE_MAX = 1U << 20, /* non-ABI */ > + > + __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63, > }; > > > Is this supposed to be a user-visible interface? > > I realize that if the user tries to set anything above PERF_SAMPLE_MAX > it will be caught and flagged as EINVAL. > > However even with the double-underscore hint in > __PERF_SAMPLE_CALLCHAIN_EARLY the value is still in the user-visible > header so it's now part of the ABI and I guess the manpage has to document it. Hurphm.. visible yes, but as you say, also quite useless. Does it really make sense to document that?