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2.4-ac: separate max RT from max user RT

PATCH In review Robert Love 2 participants 2 messages May 7, 2002

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Robert Love

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PATCH 1/1 2.4-ac: separate max RT from max user RT

Alan,

The attached patch separates the notion of "maximum real-time priority" from what we actually export to user-space. This will also us, in the future, to have kernel threads with a greater RT priority than any user task.

Right now the two values are set equal and thus the patch has no object code changes. It does provide a bit of a cleanup, however.

Patch is against 2.4.19-pre7-ac4, please apply.

Robert Love

kernel/sched.c +15 -11
diff -urN linux-2.4.19-pre7-ac4/kernel/sched.c linux/kernel/sched.c
@@ -22,13 +22,17 @@
 #include <linux/kernel_stat.h>
 
 /*
- * Priority of a process goes from 0 to MAX_PRIO-1.  The
- * 0 to MAX_RT_PRIO-1 priority range is allocated to RT tasks,
- * the MAX_RT_PRIO to MAX_PRIO range is for SCHED_OTHER tasks.
- * Priority values are inverted: lower p->prio value means higher
- * priority.
+ * Priority of a process goes from 0 to 139. The 0-99
+ * priority range is allocated to RT tasks, the 100-139
+ * range is for SCHED_OTHER tasks. Priority values are
+ * inverted: lower p->prio value means higher priority.
+ * 
+ * MAX_USER_RT_PRIO allows the actual maximum RT priority
+ * to be separate from the value exported to user-space.
+ * NOTE: MAX_RT_PRIO must not be smaller than MAX_USER_RT_PRIO.
  */
 #define MAX_RT_PRIO		100
+#define MAX_USER_RT_PRIO	100
 #define MAX_PRIO		(MAX_RT_PRIO + 40)
 
 /*

@@ -1025,7 +1029,7 @@
  */
 int task_prio(task_t *p)
 {
-	return p->prio - MAX_RT_PRIO;
+	return p->prio - MAX_USER_RT_PRIO;
 }
 
 int task_nice(task_t *p)

@@ -1082,11 +1086,11 @@
 	}
 
 	/*
-	 * Valid priorities for SCHED_FIFO and SCHED_RR are 1..MAX_RT_PRIO-1,
-	 * valid priority for SCHED_OTHER is 0.
+	 * Valid priorities for SCHED_FIFO and SCHED_RR are
+	 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_OTHER is 0.
 	 */
 	retval = -EINVAL;
-	if (lp.sched_priority < 0 || lp.sched_priority > MAX_RT_PRIO - 1)
+	if (lp.sched_priority < 0 || lp.sched_priority > MAX_USER_RT_PRIO-1)
 		goto out_unlock;
 	if ((policy == SCHED_OTHER) != (lp.sched_priority == 0))
 		goto out_unlock;

@@ -1106,7 +1110,7 @@
 	p->policy = policy;
 	p->rt_priority = lp.sched_priority;
 	if (policy != SCHED_OTHER)
-		p->prio = (MAX_RT_PRIO - 1) - p->rt_priority;
+		p->prio = MAX_USER_RT_PRIO-1 - p->rt_priority;
 	else
 		p->prio = p->static_prio;
 	if (array)

@@ -1229,7 +1233,7 @@
 	switch (policy) {
 	case SCHED_FIFO:
 	case SCHED_RR:
-		ret = MAX_RT_PRIO - 1;
+		ret = MAX_USER_RT_PRIO-1;
 		break;
 	case SCHED_OTHER:
 		ret = 0;