Deprecate find_task_by_pid()

There are some places that are known to operate on tasks'
global pids only:

* the rest_init() call (called on boot)
* the kgdb's getthread
* the create_kthread() (since the kthread is run in init ns)

So use the find_task_by_pid_ns(..., &init_pid_ns) there
and schedule the find_task_by_pid for removal.

[sukadev@us.ibm.com: Fix warning in kernel/pid.c]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/kthread.c b/kernel/kthread.c
index ac72eea..bd1b9ea 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -98,7 +98,7 @@
 		struct sched_param param = { .sched_priority = 0 };
 		wait_for_completion(&create->started);
 		read_lock(&tasklist_lock);
-		create->result = find_task_by_pid(pid);
+		create->result = find_task_by_pid_ns(pid, &init_pid_ns);
 		read_unlock(&tasklist_lock);
 		/*
 		 * root may have changed our (kthreadd's) priority or CPU mask.