Messages in this thread Patch in this message | | | Date | Mon, 10 Feb 2014 09:09:48 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 1/3] sched: Move the priority specific bits into a new header file. |
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On Mon, 10 Feb 2014 10:56:34 +0800 Dongsheng Yang <yangds.fnst@cn.fujitsu.com> wrote:
> >> diff --git a/include/linux/sched.h b/include/linux/sched.h > >> index 68a0e84..ba1b732 100644 > >> --- a/include/linux/sched.h > >> +++ b/include/linux/sched.h > >> @@ -3,6 +3,10 @@ > >> > >> #include <uapi/linux/sched.h> > >> > >> +#ifndef _SCHED_PRIO_H > >> +#include <linux/sched/prio.h> > >> +#endif /* #ifndef _SCHED_PRIO_H */ > > It seems you don't need to use #ifndef-#endif pair to include a header > > file? > > Sorry for the late reply, coming back from vacation for Chinese Spring > Festival. > > The reason I use #ifndef-#endif here is that there are lots of files, > such as kernel/sched/sched.h, are including <linux/sched.h> and > <linux/sched/rt.h>. And both of them are including prio.h. > > I am not sure should we avoid reincluding a file and how. > > Could you help to give me some suggestion of it. Thanx :)
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.
-- Steve
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