kthread: reduce stack pressure in create_kthread and kthreadd

  * Replace:

  	set_cpus_allowed(..., CPU_MASK_ALL)

    with:

  	set_cpus_allowed_ptr(..., CPU_MASK_ALL_PTR)

    to remove excessive stack requirements when NR_CPUS=4096.

Signed-off-by: Mike Travis <travis@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/kthread.c

@@ -106,7 +106,7 @@ static void create_kthread(struct kthread_create_info *create)
 		 */
 		sched_setscheduler(create->result, SCHED_NORMAL, &param);
 		set_user_nice(create->result, KTHREAD_NICE_LEVEL);
-		set_cpus_allowed(create->result, CPU_MASK_ALL);
+		set_cpus_allowed_ptr(create->result, CPU_MASK_ALL_PTR);
 	}
 	complete(&create->done);
 }
@@ -233,7 +233,7 @@ int kthreadd(void *unused)
 	set_task_comm(tsk, "kthreadd");
 	ignore_signals(tsk);
 	set_user_nice(tsk, KTHREAD_NICE_LEVEL);
-	set_cpus_allowed(tsk, CPU_MASK_ALL);
+	set_cpus_allowed_ptr(tsk, CPU_MASK_ALL_PTR);
 
 	current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;