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+/* 
+ * Mach Operating System
+ * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
+ * All Rights Reserved.
+ * 
+ * Permission to use, copy, modify and distribute this software and its
+ * documentation is hereby granted, provided that both the copyright
+ * notice and this permission notice appear in all copies of the
+ * software, derivative works or modified versions, and any portions
+ * thereof, and that both notices appear in supporting documentation.
+ * 
+ * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
+ * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
+ * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
+ * 
+ * Carnegie Mellon requests users of this software to return to
+ * 
+ *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
+ *  School of Computer Science
+ *  Carnegie Mellon University
+ *  Pittsburgh PA 15213-3890
+ * 
+ * any improvements or extensions that they make and grant Carnegie Mellon
+ * the rights to redistribute these changes.
+ */
+/*
+ *	File:	sched.h
+ *	Author:	Avadis Tevanian, Jr.
+ *	Date:	1985
+ *
+ *	Header file for scheduler.
+ *
+ */
+
+#ifndef	_KERN_SCHED_H_
+#define _KERN_SCHED_H_
+
+#include <cpus.h>
+#include <mach_fixpri.h>
+#include <simple_clock.h>
+#include <stat_time.h>
+
+#include <kern/queue.h>
+#include <kern/lock.h>
+#include <kern/macro_help.h>
+
+#if	MACH_FIXPRI
+#include <mach/policy.h>
+#endif	MACH_FIXPRI
+
+#if	STAT_TIME
+
+/*
+ *	Statistical timing uses microseconds as timer units.  18 bit shift
+ *	yields priorities.  PRI_SHIFT_2 isn't needed.
+ */
+#define PRI_SHIFT	18
+
+#else	STAT_TIME
+
+/*
+ *	Otherwise machine provides shift(s) based on time units it uses.
+ */
+#include <machine/sched_param.h>
+
+#endif	STAT_TIME
+#define NRQS	32			/* 32 run queues per cpu */
+
+struct run_queue {
+	queue_head_t		runq[NRQS];	/* one for each priority */
+	decl_simple_lock_data(,	lock)		/* one lock for all queues */
+	int			low;		/* low queue value */
+	int			count;		/* count of threads runable */
+};
+
+typedef struct run_queue	*run_queue_t;
+#define RUN_QUEUE_NULL	((run_queue_t) 0)
+
+#if	MACH_FIXPRI
+/*
+ *	NOTE: For fixed priority threads, first_quantum indicates
+ *	whether context switch at same priority is ok.  For timeshareing
+ *	it indicates whether preempt is ok.
+ */
+
+#define csw_needed(thread, processor) ((thread)->state & TH_SUSP ||	\
+	((processor)->runq.count > 0) ||				\
+	((thread)->policy == POLICY_TIMESHARE &&			\
+		(processor)->first_quantum == FALSE &&			\
+		(processor)->processor_set->runq.count > 0 &&		\
+		  (processor)->processor_set->runq.low <=		\
+			(thread)->sched_pri) ||				\
+	((thread)->policy == POLICY_FIXEDPRI &&				\
+		(processor)->processor_set->runq.count > 0 &&		\
+		 ((((processor)->first_quantum == FALSE) &&		\
+		  ((processor)->processor_set->runq.low <=		\
+			(thread)->sched_pri)) ||			\
+		 ((processor)->processor_set->runq.low <		\
+			(thread)->sched_pri))))
+
+#else	MACH_FIXPRI
+#define csw_needed(thread, processor) ((thread)->state & TH_SUSP ||	\
+		((processor)->runq.count > 0) ||			\
+		((processor)->first_quantum == FALSE &&			\
+		 ((processor)->processor_set->runq.count > 0 &&		\
+		  (processor)->processor_set->runq.low <=		\
+			((thread)->sched_pri))))
+#endif	MACH_FIXPRI
+
+/*
+ *	Scheduler routines.
+ */
+
+extern struct run_queue	*rem_runq();
+extern struct thread	*choose_thread();
+extern queue_head_t	action_queue;	/* assign/shutdown queue */
+decl_simple_lock_data(extern,action_lock);
+
+extern int		min_quantum;	/* defines max context switch rate */
+
+/*
+ *	Default base priorities for threads.
+ */
+#define BASEPRI_SYSTEM	6
+#define BASEPRI_USER	12
+
+/*
+ *	Macro to check for invalid priorities.
+ */
+
+#define invalid_pri(pri) (((pri) < 0) || ((pri) >= NRQS))
+
+/*
+ *	Shift structures for holding update shifts.  Actual computation
+ *	is  usage = (usage >> shift1) +/- (usage >> abs(shift2))  where the
+ *	+/- is determined by the sign of shift 2.
+ */
+struct shift {
+	int	shift1;
+	int	shift2;
+};
+
+typedef	struct shift	*shift_t, shift_data_t;
+
+/*
+ *	sched_tick increments once a second.  Used to age priorities.
+ */
+
+extern unsigned	sched_tick;
+
+#define SCHED_SCALE	128
+#define SCHED_SHIFT	7
+
+/*
+ *	thread_timer_delta macro takes care of both thread timers.
+ */
+
+#define thread_timer_delta(thread)  				\
+MACRO_BEGIN							\
+	register unsigned	delta;				\
+								\
+	delta = 0;						\
+	TIMER_DELTA((thread)->system_timer,			\
+		(thread)->system_timer_save, delta);		\
+	TIMER_DELTA((thread)->user_timer,			\
+		(thread)->user_timer_save, delta);		\
+	(thread)->cpu_delta += delta;				\
+	(thread)->sched_delta += delta * 			\
+			(thread)->processor_set->sched_load;	\
+MACRO_END
+
+#if	SIMPLE_CLOCK
+/*
+ *	sched_usec is an exponential average of number of microseconds
+ *	in a second for clock drift compensation.
+ */
+
+extern int	sched_usec;
+#endif	SIMPLE_CLOCK
+
+#endif	_KERN_SCHED_H_