linux-kernel - [PATCH 1/3] sched: Remove MAX_USER_RT

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Message-Id: <20210128131040.296856-2-dietmar.eggemann@arm.com>
Date:   Thu, 28 Jan 2021 14:10:38 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jeremy Kerr <jk@...abs.org>, Arnd Bergmann <arnd@...db.de>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Hillf Danton <hdanton@...a.com>, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 1/3] sched: Remove MAX_USER_RT_PRIO

Commit d46523ea32a7 ("[PATCH] fix MAX_USER_RT_PRIO and MAX_RT_PRIO")
was introduced due to a a small time period in which the realtime patch
set was using different values for MAX_USER_RT_PRIO and MAX_RT_PRIO.

This is no longer true, i.e. now MAX_RT_PRIO == MAX_USER_RT_PRIO.

Get rid of MAX_USER_RT_PRIO and make everything use MAX_RT_PRIO
instead.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
---
 include/linux/sched/prio.h | 9 +--------
 kernel/sched/core.c        | 7 +++----
 2 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/include/linux/sched/prio.h b/include/linux/sched/prio.h
index 7d64feafc408..d111f2fd77ea 100644
--- a/include/linux/sched/prio.h
+++ b/include/linux/sched/prio.h
@@ -11,16 +11,9 @@
  * priority is 0..MAX_RT_PRIO-1, and SCHED_NORMAL/SCHED_BATCH
  * tasks are in the range MAX_RT_PRIO..MAX_PRIO-1. Priority
  * values are inverted: lower p->prio value means higher priority.
- *
- * The MAX_USER_RT_PRIO value allows the actual maximum
- * RT priority to be separate from the value exported to
- * user-space.  This allows kernel threads to set their
- * priority to a value higher than any user task. Note:
- * MAX_RT_PRIO must not be smaller than MAX_USER_RT_PRIO.
  */
 
-#define MAX_USER_RT_PRIO	100
-#define MAX_RT_PRIO		MAX_USER_RT_PRIO
+#define MAX_RT_PRIO		100
 
 #define MAX_PRIO		(MAX_RT_PRIO + NICE_WIDTH)
 #define DEFAULT_PRIO		(MAX_RT_PRIO + NICE_WIDTH / 2)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 06b449942adf..625ec1e12064 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5897,11 +5897,10 @@ static int __sched_setscheduler(struct task_struct *p,
 
 	/*
 	 * Valid priorities for SCHED_FIFO and SCHED_RR are
-	 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
+	 * 1..MAX_RT_PRIO-1, valid priority for SCHED_NORMAL,
 	 * SCHED_BATCH and SCHED_IDLE is 0.
 	 */
-	if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
-	    (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
+	if (attr->sched_priority > MAX_RT_PRIO-1)
 		return -EINVAL;
 	if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
 	    (rt_policy(policy) != (attr->sched_priority != 0)))
@@ -6969,7 +6968,7 @@ SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
 	switch (policy) {
 	case SCHED_FIFO:
 	case SCHED_RR:
-		ret = MAX_USER_RT_PRIO-1;
+		ret = MAX_RT_PRIO-1;
 		break;
 	case SCHED_DEADLINE:
 	case SCHED_NORMAL:
-- 
2.25.1