sched: Remove USER_PRIO, TASK_USER_PRIO and MAX_USER_PRIO

The only remaining use of MAX_USER_PRIO (and USER_PRIO) is the
SCALE_PRIO() definition in the PowerPC Cell architecture's Synergistic
Processor Unit (SPU) scheduler. TASK_USER_PRIO isn't used anymore.

Commit fe443ef2 ("[POWERPC] spusched: Dynamic timeslicing for
SCHED_OTHER") copied SCALE_PRIO() from the task scheduler in v2.6.23.

Commit a4ec24b4 ("sched: tidy up SCHED_RR") removed it from the task
scheduler in v2.6.24.

Commit 3ee237dd ("sched/prio: Add 3 macros of MAX_NICE, MIN_NICE and
NICE_WIDTH in prio.h") introduced NICE_WIDTH much later.

With:

  MAX_USER_PRIO = USER_PRIO(MAX_PRIO)

                = MAX_PRIO - MAX_RT_PRIO

       MAX_PRIO = MAX_RT_PRIO + NICE_WIDTH

  MAX_USER_PRIO = MAX_RT_PRIO + NICE_WIDTH - MAX_RT_PRIO

  MAX_USER_PRIO = NICE_WIDTH

MAX_USER_PRIO can be replaced by NICE_WIDTH to be able to remove all the
{*_}USER_PRIO defines.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210128131040.296856-3-dietmar.eggemann@arm.com

arch/powerpc/platforms/cell/spufs/sched.c

@@ -72,7 +72,7 @@ static struct timer_list spuloadavg_timer;
 #define DEF_SPU_TIMESLICE	(100 * HZ / (1000 * SPUSCHED_TICK))
 
 #define SCALE_PRIO(x, prio) \
-	max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_SPU_TIMESLICE)
+	max(x * (MAX_PRIO - prio) / (NICE_WIDTH / 2), MIN_SPU_TIMESLICE)
 
 /*
  * scale user-nice values [ -20 ... 0 ... 19 ] to time slice values:

include/linux/sched/prio.h

@@ -26,15 +26,6 @@
 #define NICE_TO_PRIO(nice)	((nice) + DEFAULT_PRIO)
 #define PRIO_TO_NICE(prio)	((prio) - DEFAULT_PRIO)
 
-/*
- * 'User priority' is the nice value converted to something we
- * can work with better when scaling various scheduler parameters,
- * it's a [ 0 ... 39 ] range.
- */
-#define USER_PRIO(p)		((p)-MAX_RT_PRIO)
-#define TASK_USER_PRIO(p)	USER_PRIO((p)->static_prio)
-#define MAX_USER_PRIO		(USER_PRIO(MAX_PRIO))
-
 /*
  * Convert nice value [19,-20] to rlimit style value [1,40].
  */

kernel/sched/sched.h

@@ -140,7 +140,7 @@ extern void call_trace_sched_update_nr_running(struct rq *rq, int count);
  * scale_load() and scale_load_down(w) to convert between them. The
  * following must be true:
  *
- *  scale_load(sched_prio_to_weight[USER_PRIO(NICE_TO_PRIO(0))]) == NICE_0_LOAD
+ *  scale_load(sched_prio_to_weight[NICE_TO_PRIO(0)-MAX_RT_PRIO]) == NICE_0_LOAD
  *
  */
 #define NICE_0_LOAD		(1L << NICE_0_LOAD_SHIFT)