sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check

commit 6227cb00cc120f9a43ce8313bb0475ddabcb7d01 upstream.

The check at the beginning of cpupri_find() makes sure that the task_pri
variable does not exceed the cp->pri_to_cpu array length. But that length
is CPUPRI_NR_PRIORITIES not MAX_RT_PRIO, where it will miss the last two
priorities in that array.

As task_pri is computed from convert_prio() which should never be bigger
than CPUPRI_NR_PRIORITIES, if the check should cause a panic if it is
hit.

Change-Id: Idc7b4e236f26edeaea86aad255cfd810ac847630
Reported-by: Mike Galbraith <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

kernel/sched/cpupri.c

@@ -68,8 +68,7 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p,
 	int                  idx      = 0;
 	int                  task_pri = convert_prio(p->prio);
 
-	if (task_pri >= MAX_RT_PRIO)
-		return 0;
+	BUG_ON(task_pri >= CPUPRI_NR_PRIORITIES);
 
 	for (idx = 0; idx < task_pri; idx++) {
 		struct cpupri_vec *vec  = &cp->pri_to_cpu[idx];