From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755110AbbCRJPw (ORCPT <rfc822;w@1wt.eu>);
	Wed, 18 Mar 2015 05:15:52 -0400
Received: from bombadil.infradead.org ([198.137.202.9]:56837 "EHLO
	bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754488AbbCRJPt (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 18 Mar 2015 05:15:49 -0400
Date: Wed, 18 Mar 2015 10:15:27 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Vinson Lee <vlee@twopensource.com>
Cc: Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>, Adrian Hunter <adrian.hunter@intel.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Namhyung Kim <namhyung@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-perf-users@vger.kernel.org,
        Vinson Lee <vlee@twitter.com>, Yann Droneaud <ydroneaud@opteya.com>
Subject: Re: [PATCH] perf tools: Work around lack of sched_getcpu in glibc <
 2.6.
Message-ID: <20150318091527.GM23123@twins.programming.kicks-ass.net>
References: <1423879609-4373-1-git-send-email-vlee@twopensource.com>
 <1424119815.32606.14.camel@opteya.com>
 <CAHTgTXVQZDk4Eu8=aVU+fojFNNZ8Fm2aL0W5s0Rmd1aHNe76rQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAHTgTXVQZDk4Eu8=aVU+fojFNNZ8Fm2aL0W5s0Rmd1aHNe76rQ@mail.gmail.com>
User-Agent: Mutt/1.5.21 (2012-12-30)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Mar 17, 2015 at 04:49:13PM -0700, Vinson Lee wrote:
> On Mon, Feb 16, 2015 at 12:50 PM, Yann Droneaud <ydroneaud@opteya.com> wrote:
> >> +#ifdef __GLIBC_PREREQ
> >> +#if __GLIBC_PREREQ(2, 6)
> >> +#define HAVE_SCHED_GETCPU
> >> +#endif
> >> +#endif

> >> @@ -21,9 +27,13 @@ static int perf_flag_probe(void)
> >>       pid_t pid = -1;
> >>       char sbuf[STRERR_BUFSIZE];
> >>
> >> +#ifdef HAVE_SCHED_GETCPU
> >>       cpu = sched_getcpu();
> >>       if (cpu < 0)
> >>               cpu = 0;
> >> +#else
> >> +     cpu = 0;
> >> +#endif
> >>
> >>       while (1) {
> >>               /* check cloexec flag */

Would it not be much nicer to implement a sched_getcpu() stub that
returns -1 and sets errno to -ENOSYS or something?

That avoids the magic #ifdef mushroom.