/* task.h */

/* EMACS_MODES: c !fill */

/* This file contains the definitions for the UNIX tasking package.  This
 * package requires the general-purpose queuing package.
 */

#include	"q.h"

typedef	int	stack;			/* type of data in task's stack */
typedef	int	event;			/* an event flag */

typedef	struct	task	{		/* a UNIX task - top of its stack */
	struct	q_elt	tk_elt;		/* next task ptr */
	stack	*tk_fp;			/* task's current frame ptr */
	unsigned tk_state;		/* task's state: run, ready, blocked */
	event	tk_evf;			/* task's wakeup event flag */
	caddr_t	tk_extern;		/* task's external static vars. */
	stack	tk_stack[1];		/* top of task's stack */
} task;

typedef	struct	task_q	{		/* a task queue */
	task	*tq_head;		/* first task in queue */
	task	*tq_tail;		/* last task in queue */
	int	tq_len;			/* number of tasks in queue */
} task_q;


extern	task	*tk_cur;		/* currently running task */
extern	task_q	tk_rdy;			/* queue of ready tasks */
extern	task_q	tk_blk;			/* queue of blocked tasks */
extern	int	tk_resched;		/* reschedule needed flag */
extern	task	*tk_init ();		/* initialize task system */
extern	task	*tk_fork ();		/* fork a new task */


#define	TK_SYSLEEP	30		/* time to block process */


/* Definitions for task states */

#define	TK_RUN		1		/* task is currently running */
#define	TK_RDY		2		/* task is on ready queue */
#define	TK_BLK		3		/* task is on blocked queue */
#define	TK_DEAD		4		/* task has exited */


/* Useful macros */

/* Wakeup a specified task.  May be used at interrupt level */

#define	tk_wake(tk)	{ (tk)->tk_evf = TRUE; tk_resched = TRUE; }

/* Wakeup a task and set the specified event flag for it */

#define	tk_setef(tk,ef) { *(ef) = TRUE; (tk)->tk_evf = TRUE; tk_resched = TRUE; }

/* Block the current task and force a reschedule. */

#define	tk_block() { \
	tk_cur->tk_state = TK_BLK; \
	q_addt (&tk_blk, tk_cur); \
	tk_sched (); \
}

/* Yield the processor to any other runnable task */

#define	tk_yield()	{ tk_wake(tk_cur); tk_block(); }