Index: linux-2.6.15-rc1-ck1/include/linux/sched.h
===================================================================
--- linux-2.6.15-rc1-ck1.orig/include/linux/sched.h	2005-11-12 20:53:15.000000000 +1100
+++ linux-2.6.15-rc1-ck1/include/linux/sched.h	2005-11-12 20:54:41.000000000 +1100
@@ -159,9 +159,10 @@ extern unsigned long nr_iowait(void);
 #define SCHED_FIFO		1
 #define SCHED_RR		2
 #define SCHED_BATCH		3
+#define SCHED_ISO		4
 
 #define SCHED_MIN		0
-#define SCHED_MAX		3
+#define SCHED_MAX		4
 
 #define SCHED_RANGE(policy)	((policy) >= SCHED_MIN && \
 					(policy) <= SCHED_MAX)
@@ -205,7 +206,7 @@ extern void show_stack(struct task_struc
 
 void io_schedule(void);
 long io_schedule_timeout(long timeout);
-extern int sched_interactive, sched_compute;
+extern int sched_interactive, sched_compute, sched_iso_cpu;
 
 extern void cpu_init (void);
 extern void trap_init(void);
@@ -502,6 +503,7 @@ struct signal_struct {
 
 #define rt_task(p)		(unlikely((p)->prio < MAX_RT_PRIO))
 #define batch_task(p)		((p)->policy == SCHED_BATCH)
+#define iso_task(p)		((p)->policy == SCHED_ISO)
 
 /*
  * Some day this will be a full-fledged user tracking system..
@@ -921,6 +923,7 @@ do { if (atomic_dec_and_test(&(tsk)->usa
 #define PF_HOTPLUG_CPU	0x01000000	/* Currently performing CPU hotplug */
 #define PF_NONSLEEP	0x02000000	/* Waiting on in kernel activity */
 #define PF_YIELDED	0x04000000	/* I have just yielded */
+#define PF_ISOREF	0x08000000	/* SCHED_ISO task has used up quota */
 
 /*
  * Only the _current_ task can read/write to tsk->flags, but other
Index: linux-2.6.15-rc1-ck1/include/linux/sysctl.h
===================================================================
--- linux-2.6.15-rc1-ck1.orig/include/linux/sysctl.h	2005-11-12 15:45:42.000000000 +1100
+++ linux-2.6.15-rc1-ck1/include/linux/sysctl.h	2005-11-12 20:54:24.000000000 +1100
@@ -149,6 +149,7 @@ enum
 	KERN_SPIN_RETRY=70,	/* int: number of spinlock retries */
 	KERN_INTERACTIVE=71,	/* interactive tasks can have cpu bursts */
 	KERN_COMPUTE=72,	/* adjust timeslices for a compute server */
+	KERN_ISO_CPU=73,	/* percent cpu SCHED_ISO tasks run SCHED_RR */
 };
 
 
Index: linux-2.6.15-rc1-ck1/kernel/sched.c
===================================================================
--- linux-2.6.15-rc1-ck1.orig/kernel/sched.c	2005-11-12 20:53:50.000000000 +1100
+++ linux-2.6.15-rc1-ck1/kernel/sched.c	2005-11-12 20:54:24.000000000 +1100
@@ -92,6 +92,9 @@ int sched_compute = 0;
 #define RR_INTERVAL()		(_RR_INTERVAL * (1 + 19 * sched_compute))
 #define DEF_TIMESLICE		(RR_INTERVAL() * 19)
 
+int sched_iso_cpu = 70;
+#define ISO_PERIOD		(3 * HZ)
+
 #define task_hot(p, now, sd) ((long long) ((now) - (p)->timestamp)	\
 				< (long long) (sd)->cache_hot_time)
 
@@ -116,6 +119,8 @@ struct runqueue {
 	 * remote CPUs use both these fields when doing load calculation.
 	 */
 	unsigned long nr_running;
+	unsigned long iso_ticks;
+	unsigned int iso_refractory;
 #ifdef CONFIG_SMP
 	unsigned long prio_bias;
 	unsigned long cpu_load[3];
@@ -721,6 +726,15 @@ static int effective_prio(task_t *p)
 		}
 		return MAX_PRIO - 1;
 	}
+	if (iso_task(p)) {
+		if (likely(!(p->flags & PF_ISOREF)))
+			/*
+			 * If SCHED_ISO tasks have not used up their real time
+			 * quota they have highest SCHED_NORMAL priority.
+			 * Otherwise they run as SCHED_NORMAL.
+			 */
+			return MAX_RT_PRIO;
+	}
 
 	full_slice = slice(p);
 	if (full_slice > p->slice)
@@ -2525,6 +2539,22 @@ static void time_slice_expired(task_t *p
 }
 
 /*
+ * Test if SCHED_ISO tasks have run longer than their alloted period as RT
+ * tasks and set the refractory flag if necessary. There is 10% hysteresis
+ * for unsetting the flag.
+ */
+static inline unsigned int test_ret_isorefractory(runqueue_t *rq)
+{
+	if (likely(!rq->iso_refractory)) {
+		if (rq->iso_ticks / ISO_PERIOD > sched_iso_cpu)
+			rq->iso_refractory = 1;
+	} else
+		if (rq->iso_ticks / ISO_PERIOD < (sched_iso_cpu * 90 / 100))
+			rq->iso_refractory = 0;
+	return rq->iso_refractory;
+}
+
+/*
  * This function gets called by the timer code, with HZ frequency.
  * We call it with interrupts disabled.
  */
@@ -2552,15 +2582,34 @@ void scheduler_tick(void)
 		set_tsk_need_resched(p);
 		goto out;
 	}
+
+	spin_lock(&rq->lock);
+	if (unlikely((rt_task(p) || (iso_task(p) && !rq->iso_refractory)) &&
+		p->mm)) {
+			rq->iso_ticks += 100;
+			if (rq->iso_ticks > ISO_PERIOD * 100)
+				rq->iso_ticks = ISO_PERIOD * 100;
+	} else
+		rq->iso_ticks = rq->iso_ticks * (ISO_PERIOD - 1) / ISO_PERIOD;
+
+	if (unlikely(test_ret_isorefractory(rq))) {
+		if (iso_task(p)) {
+			if (!(p->flags & PF_ISOREF)) {
+				set_tsk_need_resched(p);
+				p->flags |= PF_ISOREF;
+			}
+		}
+	} else if (iso_task(p))
+		p->flags &= ~PF_ISOREF;
+
 	/*
 	 * SCHED_FIFO tasks never run out of timeslice.
 	 */
 	if (unlikely(p->policy == SCHED_FIFO)) {
 		expired_balance = 0;
-		goto out;
+		goto out_unlock;
 	}
 
-	spin_lock(&rq->lock);
 	debit = ns_diff(rq->timestamp_last_tick, p->timestamp);
 	p->ns_debit += debit;
 	if (p->ns_debit < NSJIFFY)
@@ -2698,7 +2747,7 @@ static inline int dependent_sleeper(int 
 		task_t *smt_curr = smt_rq->curr;
 
 		/* Kernel threads do not participate in dependent sleeping */
-		if (!p->mm || !smt_curr->mm || rt_task(p))
+		if (!p->mm || !smt_curr->mm || rt_task(p) || iso_task(p))
 			goto check_smt_task;
 
 		/*
@@ -2736,7 +2785,7 @@ static inline int dependent_sleeper(int 
 
 check_smt_task:
 		if ((!smt_curr->mm && smt_curr != smt_rq->idle) ||
-			rt_task(smt_curr))
+			rt_task(smt_curr) || iso_task(smt_curr))
 				continue;
 		if (!p->mm) {
 			wakeup_busy_runqueue(smt_rq);
@@ -3553,9 +3602,19 @@ int sched_setscheduler(struct task_struc
 {
 	int retval;
 	int queued, oldprio, oldpolicy = -1;
+	struct sched_param zero_param = { .sched_priority = 0 };
 	unsigned long flags;
 	runqueue_t *rq;
 
+	if (SCHED_RT(policy) && !capable(CAP_SYS_NICE)) {
+		/*
+		 * If the caller requested an RT policy without having the
+		 * necessary rights, we downgrade the policy to SCHED_ISO.
+		 * We also set the parameter to zero to pass the checks.
+		 */
+		policy = SCHED_ISO;
+		param = &zero_param;
+	}
 recheck:
 	/* double check policy once rq lock held */
 	if (policy < 0)
@@ -4052,6 +4111,7 @@ asmlinkage long sys_sched_get_priority_m
 		break;
 	case SCHED_NORMAL:
 	case SCHED_BATCH:
+	case SCHED_ISO:
 		ret = 0;
 		break;
 	}
@@ -4076,6 +4136,7 @@ asmlinkage long sys_sched_get_priority_m
 		break;
 	case SCHED_NORMAL:
 	case SCHED_BATCH:
+	case SCHED_ISO:
 		ret = 0;
 	}
 	return ret;
@@ -5443,6 +5504,7 @@ void __init sched_init(void)
 		rq->nr_running = 0;
 		rq->cache_ticks = 0;
 		rq->preempted = 0;
+		rq->iso_ticks = 0;
 
 #ifdef CONFIG_SMP
 		rq->sd = NULL;
Index: linux-2.6.15-rc1-ck1/kernel/sysctl.c
===================================================================
--- linux-2.6.15-rc1-ck1.orig/kernel/sysctl.c	2005-11-12 15:45:42.000000000 +1100
+++ linux-2.6.15-rc1-ck1/kernel/sysctl.c	2005-11-12 20:54:24.000000000 +1100
@@ -224,6 +224,11 @@ static ctl_table root_table[] = {
 	{ .ctl_name = 0 }
 };
 
+/* Constants for minimum and maximum testing.
+   We use these as one-element integer vectors. */
+static int zero;
+static int one_hundred = 100;
+
 static ctl_table kern_table[] = {
 	{
 		.ctl_name	= KERN_OSTYPE,
@@ -634,6 +639,17 @@ static ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec,
 	},
+	{
+		.ctl_name	= KERN_ISO_CPU,
+		.procname	= "iso_cpu",
+		.data		= &sched_iso_cpu,
+		.maxlen		= sizeof (int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_minmax,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &zero,
+		.extra2		= &one_hundred,
+	},
 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
 	{
 		.ctl_name       = KERN_UNKNOWN_NMI_PANIC,
@@ -675,12 +691,6 @@ static ctl_table kern_table[] = {
 	{ .ctl_name = 0 }
 };
 
-/* Constants for minimum and maximum testing in vm_table.
-   We use these as one-element integer vectors. */
-static int zero;
-static int one_hundred = 100;
-
-
 static ctl_table vm_table[] = {
 	{
 		.ctl_name	= VM_OVERCOMMIT_MEMORY,