edf.h

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

enum {
	Maxsteps = 200 * 100 * 2,	/* 100 periods of 200 procs */

	/* Edf.flags field */
	Admitted		= 0x01,
	Sporadic		= 0x02,
	Yieldonblock		= 0x04,
	Sendnotes		= 0x08,
	Deadline		= 0x10,
	Yield			= 0x20,
	Extratime		= 0x40,

	Infinity = ~0ULL,
};

typedef struct Edf		Edf;

struct Edf {
	/* All times in µs */
	/* time intervals */
	long		D;		/* Deadline */
	long		Delta;		/* Inherited deadline */
	long		T;		/* period */
	long		C;		/* Cost */
	long		S;		/* Slice: time remaining in this period */
	/* times (only low-order bits of absolute time) */
	long		r;		/* (this) release time */
	long		d;		/* (this) deadline */
	long		t;		/* Start of next period, t += T at release */
	long		s;		/* Time at which this proc was last scheduled */
	/* for schedulability testing */
	long		testDelta;
	int		testtype;	/* Release or Deadline */
	long		testtime;
	Proc		*testnext;
	/* other */
	ushort		flags;
	Timer;
	/* Stats */
	long		edfused;
	long		extraused;
	long		aged;
	ulong		periods;
	ulong		missed;
};

extern Lock	edftestlock;	/* for atomic admitting/expelling */

#pragma	varargck	type	"t"		long
#pragma	varargck	type	"U"		uvlong

/* Interface: */
Edf*		edflock(Proc*);
void		edfunlock(void);