linux-kernel - Re: [RFC PATCH 4/5] RCU: Add TASK_RCU

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Message-ID: <20110411210223.GB2226@linux.vnet.ibm.com>
Date:	Mon, 11 Apr 2011 14:02:23 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michal Marek <mmarek@...e.cz>,
	Jan Beulich <JBeulich@...ell.com>, Ingo Molnar <mingo@...e.hu>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sam Ravnborg <sam@...nborg.org>,
	David Howells <dhowells@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC PATCH 4/5] RCU: Add TASK_RCU_OFFSET

On Mon, Apr 11, 2011 at 04:31:10PM +0800, Lai Jiangshan wrote:
> On 04/11/2011 01:12 PM, Paul E. McKenney wrote:
> 
> > -static inline struct task_struct *next_thread(const struct task_struct *p)
> > -{
> > -	return list_entry_rcu(p->thread_group.next,
> > -			      struct task_struct, thread_group);
> > -}
> > +/* Avoid #include hell for inlining rcu_read_lock(). */
> > +#define next_thread(p) \
> > +	list_entry_rcu((p)->thread_group.next, struct task_struct, thread_group)
> >  
> 
> 
> It is strange for me.
> The user of the API "next_thread(p)" must has two headers included, sched.h and rculist.h
> 
> I know this is a very popular pattern of user space code, is it OK for kernel?
> I think a file(even a header file) uses API(Marco), it should includes the the corresponding
> headers, it reduces surprises(example, the name of "next_thread()" has no "rcu",
> it is not expected that rcuxxxx.h is required).
> 
> I admit the work will become very much simpler if this pattern is allowed.

The guy who maintains much of sched.h suggested it.  ;-)

							Thanx, Paul

> man fcntl:
>        #include <unistd.h>
>        #include <fcntl.h>
> 
>        int fcntl(int fd, int cmd, ... /* arg */ );
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