patch-2.4.0-test9 linux/kernel/sched.c

• Lines: 151
• Date: Mon Oct 2 11:45:01 2000
• Orig file: v2.4.0-test8/linux/kernel/sched.c
• Orig date: Fri Sep 1 14:05:25 2000

diff -u --recursive --new-file v2.4.0-test8/linux/kernel/sched.c linux/kernel/sched.c
@@ -141,61 +141,54 @@
 	int weight;
 
 	/*
-	 * Realtime process, select the first one on the
-	 * runqueue (taking priorities within processes
-	 * into account).
+	 * select the current process after every other
+	 * runnable process, but before the idle thread.
+	 * Also, dont trigger a counter recalculation.
 	 */
-	if (p->policy != SCHED_OTHER) {
-		weight = 1000 + p->rt_priority;
+	weight = -1;
+	if (p->policy & SCHED_YIELD)
 		goto out;
-	}
 
 	/*
-	 * Give the process a first-approximation goodness value
-	 * according to the number of clock-ticks it has left.
-	 *
-	 * Don't do any other calculations if the time slice is
-	 * over..
+	 * Non-RT process - normal case first.
 	 */
-	weight = p->counter;
-	if (!weight)
-		goto out;
+	if (p->policy == SCHED_OTHER) {
+		/*
+		 * Give the process a first-approximation goodness value
+		 * according to the number of clock-ticks it has left.
+		 *
+		 * Don't do any other calculations if the time slice is
+		 * over..
+		 */
+		weight = p->counter;
+		if (!weight)
+			goto out;
 			
 #ifdef CONFIG_SMP
-	/* Give a largish advantage to the same processor...   */
-	/* (this is equivalent to penalizing other processors) */
-	if (p->processor == this_cpu)
-		weight += PROC_CHANGE_PENALTY;
+		/* Give a largish advantage to the same processor...   */
+		/* (this is equivalent to penalizing other processors) */
+		if (p->processor == this_cpu)
+			weight += PROC_CHANGE_PENALTY;
 #endif
 
-	/* .. and a slight advantage to the current MM */
-	if (p->mm == this_mm || !p->mm)
-		weight += 1;
-	weight += 20 - p->nice;
+		/* .. and a slight advantage to the current MM */
+		if (p->mm == this_mm || !p->mm)
+			weight += 1;
+		weight += 20 - p->nice;
+		goto out;
+	}
 
+	/*
+	 * Realtime process, select the first one on the
+	 * runqueue (taking priorities within processes
+	 * into account).
+	 */
+	weight = 1000 + p->rt_priority;
 out:
 	return weight;
 }
 
 /*
- * subtle. We want to discard a yielded process only if it's being
- * considered for a reschedule. Wakeup-time 'queries' of the scheduling
- * state do not count. Another optimization we do: sched_yield()-ed
- * processes are runnable (and thus will be considered for scheduling)
- * right when they are calling schedule(). So the only place we need
- * to care about SCHED_YIELD is when we calculate the previous process'
- * goodness ...
- */
-static inline int prev_goodness(struct task_struct * p, int this_cpu, struct mm_struct *this_mm)
-{
-	if (p->policy & SCHED_YIELD) {
-		p->policy &= ~SCHED_YIELD;
-		return 0;
-	}
-	return goodness(p, this_cpu, this_mm);
-}
-
-/*
  * the 'goodness value' of replacing a process on a given CPU.
  * positive value means 'replace', zero or negative means 'dont'.
  */
@@ -451,6 +444,7 @@
 static inline void __schedule_tail(struct task_struct *prev)
 {
 #ifdef CONFIG_SMP
+	int yield;
 	unsigned long flags;
 
 	/*
@@ -462,6 +456,8 @@
 	 * cache.
 	 */
 	spin_lock_irqsave(&runqueue_lock, flags);
+	yield = prev->policy & SCHED_YIELD;
+	prev->policy &= ~SCHED_YIELD;
 	prev->has_cpu = 0;
 	if (prev->state == TASK_RUNNING)
 		goto running_again;
@@ -476,9 +472,11 @@
 	 * current process as well.)
 	 */
 running_again:
-	if (prev != idle_task(smp_processor_id()))
+	if ((prev != idle_task(smp_processor_id())) && !yield)
 		reschedule_idle(prev);
 	goto out_unlock;
+#else
+	prev->policy &= ~SCHED_YIELD;
 #endif /* CONFIG_SMP */
 }
 
@@ -669,7 +667,7 @@
 	goto repeat_schedule;
 
 still_running:
-	c = prev_goodness(prev, this_cpu, prev->active_mm);
+	c = goodness(prev, this_cpu, prev->active_mm);
 	next = prev;
 	goto still_running_back;
 
@@ -1030,12 +1028,13 @@
 
 asmlinkage long sys_sched_yield(void)
 {
-	spin_lock_irq(&runqueue_lock);
+	/*
+	 * This process can only be rescheduled by us,
+	 * so this is safe without any locking.
+	 */
 	if (current->policy == SCHED_OTHER)
 		current->policy |= SCHED_YIELD;
 	current->need_resched = 1;
-	move_last_runqueue(current);
-	spin_unlock_irq(&runqueue_lock);
 	return 0;
 }