linux-kernel - Re: [tip:core/rcu] rcu: Remove inline from forward-referenced functions

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Message-ID: <20091111045013.GG8424@linux.vnet.ibm.com>
Date:	Tue, 10 Nov 2009 20:50:13 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Joe Perches <joe@...ches.com>
Cc:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:core/rcu] rcu: Remove inline from forward-referenced
	functions

On Tue, Nov 10, 2009 at 07:28:28PM -0800, Joe Perches wrote:
> On Tue, 2009-11-10 at 17:42 -0800, Paul E. McKenney wrote:
> > On Tue, Nov 10, 2009 at 05:03:41PM -0800, Joe Perches wrote:
> > > So maybe rename rcutree_plugin.h to rcutree_plugin.c and
> > > #include "rcutree_plugin.c" in rcutree.c instead.
> > Hmmm...
> 
> Perhaps something like this:

While I do very much appreciate your time and attention to this...

My problem with this sort of thing is that when I tried it, it proved
fragile.  Small changes required lots of rework of forward declarations.
Putting it at the end makes it work very nicely -- the list of forward
declarations doubles as documentation for the plugins, and the contents
of kernel/rcutree_plugin.h (or .c or whatever, either way I end up
violation about the same number of coding guidelines) is independent of
rearrangements of kernel/rcutree.c.

The reason that I would really like to keep rcu_bootup_announce() as
a function is that it makes it trivial to collect RCU-flavor-dependent
boot-time information, if needed for some debugging effort.  If I pull
the string out, this sort of thing becomes much more painful.

							Thanx, Paul

> cheers, Joe
> 
> rcu: rename rcutree_plugin.h to .c and use
> 
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index d802419..737dc72 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -1783,6 +1783,8 @@ do { \
>  	} \
>  } while (0)
> 
> +#include "rcutree_plugin.c"
> +
>  void __init __rcu_init(void)
>  {
>  	rcu_bootup_announce();
> @@ -1795,4 +1797,3 @@ void __init __rcu_init(void)
>  	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
>  }
> 
> -#include "rcutree_plugin.h"
> diff --git a/kernel/rcutree.h b/kernel/rcutree.h
> index 17a28a0..ed11d16 100644
> --- a/kernel/rcutree.h
> +++ b/kernel/rcutree.h
> @@ -300,8 +300,7 @@ DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
> 
>  #else /* #ifdef RCU_TREE_NONCORE */
> 
> -/* Forward declarations for rcutree_plugin.h */
> -static void rcu_bootup_announce(void);
> +/* Forward declarations for rcutree_plugin.c */
>  long rcu_batches_completed(void);
>  static void rcu_preempt_note_context_switch(int cpu);
>  static int rcu_preempted_readers(struct rcu_node *rnp);
> diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.c
> similarity index 99%
> rename from kernel/rcutree_plugin.h
> rename to kernel/rcutree_plugin.c
> index 52075da..5ca2d26 100644
> --- a/kernel/rcutree_plugin.h
> +++ b/kernel/rcutree_plugin.c
> @@ -33,7 +33,7 @@ DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
>  /*
>   * Tell them what RCU they are running.
>   */
> -static void rcu_bootup_announce(void)
> +static void __init rcu_bootup_announce(void)
>  {
>  	printk(KERN_INFO
>  	       "Experimental preemptable hierarchical RCU implementation.\n");
> @@ -481,7 +481,7 @@ void exit_rcu(void)
>  /*
>   * Tell them what RCU they are running.
>   */
> -static void rcu_bootup_announce(void)
> +static void __init rcu_bootup_announce(void)
>  {
>  	printk(KERN_INFO "Hierarchical RCU implementation.\n");
>  }
> 
> 
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