[PATCH] pid: add do_each_pid_task

To avoid pid rollover confusion the kernel needs to work with struct pid *
instead of pid_t.  Currently there is not an iterator that walks through all
of the tasks of a given pid type starting with a struct pid.  This prevents us
replacing some pid_t instances with struct pid.  So this patch adds
do_each_pid_task which walks through the set of task for a given pid type
starting with a struct pid.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/pid.h

@@ -119,4 +119,17 @@ extern void FASTCALL(free_pid(struct pid *pid));
 				1; }) );				\
 	}
 
+#define do_each_pid_task(pid, type, task)				\
+	if ((task = pid_task(pid, type))) {				\
+		prefetch(pid_next(task, type));				\
+		do {
+
+#define while_each_pid_task(pid, type, task)				\
+		} while (pid_next(task, type) &&  ({			\
+				task = pid_next_task(task, type);	\
+				rcu_dereference(task);			\
+				prefetch(pid_next(task, type));		\
+				1; }) );				\
+	}
+
 #endif /* _LINUX_PID_H */