From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752486AbaBKBK6 (ORCPT ); Mon, 10 Feb 2014 20:10:58 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:27147 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752131AbaBKBKz (ORCPT ); Mon, 10 Feb 2014 20:10:55 -0500 X-IronPort-AV: E=Sophos;i="4.95,821,1384272000"; d="scan'208";a="9502792" Message-ID: <52F97892.1040205@cn.fujitsu.com> Date: Tue, 11 Feb 2014 09:10:42 +0800 From: Dongsheng Yang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130612 Thunderbird/17.0.6 MIME-Version: 1.0 To: Steven Rostedt CC: Namhyung Kim , linux-kernel@vger.kernel.org, peterz@infradead.org, raistlin@linux.it, juri.lelli@gmail.com, clark.williams@gmail.com, mingo@redhat.com Subject: Re: [PATCH 1/3] sched: Move the priority specific bits into a new header file. References: <87fvo75pci.fsf@sejong.aot.lge.com> <52F83FE2.90004@cn.fujitsu.com> <20140210090948.02266f38@gandalf.local.home> In-Reply-To: <20140210090948.02266f38@gandalf.local.home> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2014/02/11 09:08:49, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2014/02/11 09:08:57, Serialize complete at 2014/02/11 09:08:57 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steven, On 02/10/2014 10:09 PM, Steven Rostedt wrote: > > > That's why you have: > > +++ b/include/linux/sched/prio.h > @@ -0,0 +1,23 @@ > +#ifndef _SCHED_PRIO_H > +#define _SCHED_PRIO_H > > The first time a header gets included, it checks if _SCHED_PRIO_H is > defined, if not, it defines it and continues. Otherwise it skips the > content of the file. > > This is so standard practice that CPP (C Pre-Processor) optimizes this > by checking if this exists and caches it. It wont even open the file > the second time it sees it included. Wow, yes. Thank you for your kind explanation. :) > > -- Steve > -- > 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/ >