Re: [PATCH] pids: simplify do_each_task_pid/while_each_task_pid

[Christoph Hellwig <hch@infradead.org>]

On Thu, Apr 13, 2006 at 08:37:27PM +0400, Oleg Nesterov wrote:
> Simpllify do_each_task_pid/while_each_task_pid macros.
> This also makes the code a bit smaller.
> 
> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
> 
> --- MM/include/linux/pid.h~	2006-03-23 22:48:10.000000000 +0300
> +++ MM/include/linux/pid.h	2006-04-13 20:28:53.000000000 +0400
> @@ -99,21 +99,16 @@ extern void FASTCALL(free_pid(struct pid
>  			pids[(type)].node)
>  
>  
> -/* We could use hlist_for_each_entry_rcu here but it takes more arguments
> - * than the do_each_task_pid/while_each_task_pid.  So we roll our own
> - * to preserve the existing interface.
> - */
> -#define do_each_task_pid(who, type, task)				\
> -	if ((task = find_task_by_pid_type(type, who))) {		\
> -		prefetch(pid_next(task, type));				\
> -		do {
> -
> -#define while_each_task_pid(who, type, task)				\
> -		} while (pid_next(task, type) &&  ({			\
> -				task = pid_next_task(task, type);	\
> -				rcu_dereference(task);			\
> -				prefetch(pid_next(task, type));		\
> -				1; }) );				\
> -	}
> +#define do_each_task_pid(who, type, task)					\
> +	do {									\
> +		struct hlist_node *pos___;					\
> +		struct pid *pid___ = find_pid(who);				\
> +		if (pid___ != NULL)						\
> +			hlist_for_each_entry_rcu((task), pos___,		\
> +				&pid___->tasks[type], pids[type].node) {
> +
> +#define while_each_task_pid(who, type, task)					\
> +			}							\
> +	} while (0)

This is prtty ugly.  Can't we just have a

#define for_each_task_pid(task, pid, type, pos) \
	hlist_for_each_entry_rcu((task), (pos),  \
		(&(pid))->tasks[type], pids[type].node) {

and move the find_pid to the caller?  That would make the code a whole lot
more readable.