sched/cpupri: Remove pri_to_cpu[1]

pri_to_cpu[1] isn't used since cpupri_set(..., newpri) is
never called with newpri = 99.

The valid RT priorities RT1..RT99 (p->rt_priority = [1..99]) map into
cpupri (idx of pri_to_cpu[]) = [2..100]

Current mapping:

p->rt_priority   p->prio   newpri   cpupri

                               -1       -1 (CPUPRI_INVALID)

                              100        0 (CPUPRI_NORMAL)

             1        98       98        2
           ...
            49        50       50       50
            50        49       49       51
           ...
            99         0        0      100

So cpupri = 1 isn't used.

Reduce the size of pri_to_cpu[] by 1 and adapt the cpupri
implementation accordingly. This will save a useless for loop with an
atomic_read in cpupri_find_fitness() calling __cpupri_find().

New mapping:

p->rt_priority   p->prio   newpri   cpupri

                               -1       -1 (CPUPRI_INVALID)

                              100        0 (CPUPRI_NORMAL)

             1        98       98        1
           ...
            49        50       50       49
            50        49       49       50
           ...
            99         0        0       99

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200922083934.19275-3-dietmar.eggemann@arm.com

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/sched/cpupri.h b/kernel/sched/cpupri.h
index 1a162369b8d4..e28e1ed12e3d 100644
--- a/kernel/sched/cpupri.h
+++ b/kernel/sched/cpupri.h
@@ -1,10 +1,10 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 
-#define CPUPRI_NR_PRIORITIES	(MAX_RT_PRIO + 1)
+#define CPUPRI_NR_PRIORITIES	MAX_RT_PRIO
 
 #define CPUPRI_INVALID		-1
 #define CPUPRI_NORMAL		 0
-/* values 2-100 are RT priorities 0-99 */
+/* values 1-99 are for RT1-RT99 priorities */
 
 struct cpupri_vec {
 	atomic_t		count;