/* Non pre-empting synchronization kernel, machine-independent portion
 * Copyright 1991 Phil Karn, KA9Q
 */

#define	SUSPEND_PROC	1

#if	defined(PROCLOG) || defined(PROCTRACE)
#include <stdio.h>
#endif
#include <dos.h>
#include <setjmp.h>
#include "global.h"
#include "mbuf.h"
#include "proc.h"
#include "timer.h"
#include "socket.h"
#include "daemon.h"
#include "hardware.h"

#ifdef	PROCLOG
FILE *proclog;
FILE *proctrace;
#endif
int Stkchk = 0;
struct proc *Curproc;		/* Currently running process */
struct proc *Rdytab;		/* Processes ready to run (not including curproc) */
struct proc *Waittab[PHASH];	/* Waiting process list */
struct proc *Susptab;		/* Suspended processes */
static struct mbuf *Killq;

static void addproc __ARGS((struct proc *entry));
static void delproc __ARGS((struct proc *entry));

/* Create a process descriptor for the main function. Must be actually
 * called from the main function!
 * Note that standard I/O is NOT set up here.
 */
struct proc *
mainproc(name)
char *name;
{
	register struct proc *pp;

	/* Create process descriptor */
	pp = (struct proc *)callocw(1,sizeof(struct proc));

	/* Create name */
	pp->name = strdup(name);
#ifndef	AMIGA
	pp->stksize = 0;
#else
	init_psetup(pp);
#endif
	/* Make current */
	pp->state = READY;
	Curproc = pp;

#ifdef	PROCLOG
	proclog = fopen("proclog",APPEND_TEXT);
	proctrace = fopen("proctrace",APPEND_TEXT);
#endif
	return pp;
}
/* Create a new, ready process and return pointer to descriptor.
 * The general registers are not initialized, but optional args are pushed
 * on the stack so they can be seen by a C function.
 */
struct proc *
newproc(name,stksize,pc,iarg,parg1,parg2,freeargs)
char *name;		/* Arbitrary user-assigned name string */
unsigned int stksize;	/* Stack size in words to allocate */
void (*pc)();		/* Initial execution address */
int iarg;		/* Integer argument (argc) */
void *parg1;		/* Generic pointer argument #1 (argv) */
void *parg2;		/* Generic pointer argument #2 (session ptr) */
int freeargs;		/* If set, free arg list on parg1 at termination */
{
	register struct proc *pp;
	int i;

	if(Stkchk)
		chkstk();

	/* Create process descriptor */
	pp = (struct proc *)callocw(1,sizeof(struct proc));

	/* Create name */
	pp->name = strdup(name);

	/* Allocate stack */
#ifdef	AMIGA
	stksize += 2000;	/* DOS overhead */
#endif
	pp->stksize = stksize;
	if((pp->stack = (int16 *)malloc(sizeof(int16)*stksize)) == NULL){
		free(pp->name);
		free((char *)pp);
		return NULLPROC;
	}
	/* Initialize stack for high-water check */
	for(i=0;i<stksize;i++)
		pp->stack[i] = STACKPAT;

	/* Do machine-dependent initialization of stack */
	psetup(pp,iarg,parg1,parg2,pc);

	pp->freeargs = freeargs;
	pp->iarg = iarg;
	pp->parg1 = parg1;
	pp->parg2 = parg2;
	
	/* Inherit creator's input and output sockets */
	usesock(Curproc->input);
	pp->input = Curproc->input;
	usesock(Curproc->output);
	pp->output = Curproc->output;

	/* Add to ready process table */
	pp->state = READY;
	addproc(pp);
	return pp;
}

/* Free resources allocated to specified process. If a process wants to kill
 * itself, the reaper is called to do the dirty work. This avoids some
 * messy situations that would otherwise occur, like freeing your own stack.
 */
void
killproc(pp)
register struct proc *pp;
{
	char **argv;

	if(pp == NULLPROC)
		return;
	/* Don't check the stack here! Will cause infinite recursion if
	 * called from a stack error
	 */

	if(pp == Curproc)
		killself();	/* Doesn't return */
	/* Close any open sockets */
	freesock(pp);

	/* Stop alarm clock in case it's running */
	stop_timer(&pp->alarm);

	/* Alert everyone waiting for this proc to die */
	psignal(pp,0);

	/* Remove from appropriate table */
	delproc(pp);

#ifdef	PROCLOG
	fprintf(proclog,"id %lx name %s stack %u/%u\n",ptol(pp),
		pp->name,stkutil(pp),pp->stksize);
	fclose(proclog);
	proclog = fopen("proclog",APPEND_TEXT);
	proctrace = fopen("proctrace",APPEND_TEXT);
#endif
	/* Free allocated memory resources */
	if(pp->freeargs){
		argv = pp->parg1;
		while(pp->iarg-- != 0)
			free(*argv++);
		free(pp->parg1);
	}
	free(pp->name);
	free(pp->stack);
	free(pp->outbuf);
	free((char *)pp);
}
/* Terminate current process by sending a request to the killer process.
 * Automatically called when a process function returns. Does not return.
 */
void
killself()
{
	register struct mbuf *bp;

	if(Curproc != NULLPROC){
		bp = pushdown(NULLBUF,sizeof(Curproc));
		memcpy(bp->data,(char *)&Curproc,sizeof(Curproc));
		enqueue(&Killq,bp);
	}
	/* "Wait for me; I will be merciful and quick." */
	for(;;)
		pwait(NULL);
}
/* Process used by processes that want to kill themselves */
void
killer(i,v1,v2)
int i;
void *v1;
void *v2;
{
	struct proc *pp;
	struct mbuf *bp;

	for(;;){
		while(Killq == NULLBUF)
			pwait(&Killq);
		bp = dequeue(&Killq);
		pullup(&bp,(char *)&pp,sizeof(pp));
		free_p(bp);
		if(pp != Curproc)	/* We're immortal */
			killproc(pp);
	}						
}

#ifdef	SUSPEND_PROC
/* Inhibit a process from running */
void
suspend(pp)
struct proc *pp;
{
	if(pp == NULLPROC)
		return;
	if(pp != Curproc)
		delproc(pp);	/* Running process isn't on any list */
	pp->state |= SUSPEND;
	if(pp != Curproc)
		addproc(pp);	/* pwait will do it for us */
	else
		pwait(NULL);
}
/* Restart suspended process */
void
resume(pp)
struct proc *pp;
{
	if(pp == NULLPROC)
		return;
	delproc(pp);	/* Can't be Curproc! */
	pp->state &= ~SUSPEND;
	addproc(pp);
}
#endif	/* SUSPEND_PROC */

/* Wakeup waiting process, regardless of event it's waiting for. The process
 * will see a return value of "val" from its pwait() call.
 */
void
alert(pp,val)
struct proc *pp;
int val;
{
	if(pp == NULLPROC)
		return;
#ifdef	notdef
	if((pp->state & WAITING) == 0)
		return;
#endif
#ifdef	PROCTRACE
	printf("alert(%lx,%u) [%s]\n",ptol(pp),val,pp->name);
	fflush(stdout);
#endif
	if(pp != Curproc)
		delproc(pp);
	pp->state &= ~WAITING;
	pp->retval = val;
	pp->event = 0;
	if(pp != Curproc)
		addproc(pp);
}

/* Post a wait on a specified event and give up the CPU until it happens. The
 * null event is special: it means "I don't want to block on an event, but let
 * somebody else run for a while". It can also mean that the present process
 * is terminating; in this case the wait never returns.
 *
 * Pwait() returns 0 if the event was signaled; otherwise it returns the
 * arg in an alert() call. Pwait must not be called from interrupt level.
 *
 * Note that pwait can run with interrupts enabled even though it examines
 * a few global variables that can be modified by psignal at interrupt time.
 * These *seem* safe.
 */
int
pwait(event)
void *event;
{
	register struct proc *oldproc;
	int tmp;

	if(Curproc != NULLPROC){	/* If process isn't terminating */
		if(Stkchk)
			chkstk();

		if(event == NULL){
			/* Special case; just give up the processor.
			 *
			 * Optimization: if nothing else is ready, just return.
			 */
			if(Rdytab == NULLPROC){
				return 0;
			}
		} else {
			/* Post a wait for the specified event */
			Curproc->event = event;
			Curproc->state = WAITING;
		}
		addproc(Curproc);
	}
	/* Look for a ready process and run it. If there are none,
	 * loop or halt until an interrupt makes something ready.
	 */
	while(Rdytab == NULLPROC){
		/* Give system back to upper-level multitasker, if any.
		 * Note that this function enables interrupts internally
		 * to prevent deadlock, but it restores our state
		 * before returning.
		 */
		kbint();	/***/
		giveup();
	}
	/* Remove first entry from ready list */
	oldproc = Curproc;
	Curproc = Rdytab;
	delproc(Curproc);

	/* Now do the context switch.
	 * This technique was inspired by Rob, PE1CHL, and is a bit tricky.
	 *
	 * If the old process has gone away, simply load the new process's
	 * environment. Otherwise, save the current process's state. Then if
	 * this is still the old process, load the new environment. Since the
	 * new task will "think" it's returning from the setjmp() with a return
	 * value of 1, the comparison with 0 will bypass the longjmp(), which
	 * would otherwise cause an infinite loop.
	 */
#ifdef	PROCTRACE
	if(strcmp(oldproc->name,Curproc->name) != 0){
	  	printf("-> %s(%d)\n",Curproc->name,!!Curproc->i_state);
		fflush(stdout);
	}
#endif
	/* Note use of comma operator to save old interrupt state only if
	 * oldproc is non-null
	 */
	if(oldproc == NULLPROC
	 || (oldproc->i_state = istate(), setjmp(oldproc->env) == 0)){
		/* We're still running in the old task; load new task context.
		 * The interrupt state is restored here in case longjmp
		 * doesn't do it (e.g., systems other than Turbo-C).
		 */
		restore(Curproc->i_state);
		longjmp(Curproc->env,1);
	}
	/* At this point, we're running in the newly dispatched task */
	tmp = Curproc->retval;
	Curproc->retval = 0;

	/* Also restore the true interrupt state here, in case the longjmp
	 * DOES restore the interrupt state saved at the time of the setjmp().
	 * This is the case with Turbo-C's setjmp/longjmp.
	 */
	restore(Curproc->i_state);
	return tmp;
}

/* Make ready the first 'n' processes waiting for a given event. The ready
 * processes will see a return value of 0 from pwait().  Note that they don't
 * actually get control until we explicitly give up the CPU ourselves through
 * a pwait(). Psignal may be called from interrupt level. It returns the
 * number of processes that were woken up.
 */
int
psignal(event,n)
void *event;	/* Event to signal */
int n;		/* Max number of processes to wake up */
{
	register struct proc *pp;
	struct proc *pnext;
	int i_state;
	unsigned int hashval;
	int cnt = 0;

	if(Stkchk)
		chkstk();

	if(event == NULL)
		return 0;		/* Null events are invalid */

	/* n = 0 means "signal everybody waiting for this event" */
	if(n == 0)
		n = 65535;

	hashval = phash(event);
	i_state = dirps();
	for(pp = Waittab[hashval];n != 0 && pp != NULLPROC;pp = pnext){
		pnext = pp->next;
		if(pp->event == event){
#ifdef	PROCTRACE
			if(i_state){
				printf("psignal(%lx,%u) wake %lx [%s]\n",ptol(event),n,
				 ptol(pp),pp->name);
				fflush(stdout);
			}
#endif
			delproc(pp);
			pp->state &= ~WAITING;
			pp->retval = 0;
			pp->event = NULL;
			addproc(pp);
			n--;
			cnt++;
		}
	}
#ifdef	SUSPEND_PROC
	for(pp = Susptab;n != 0 && pp != NULLPROC;pp = pnext){
		pnext = pp->next;
		if(pp->event == event){
#ifdef	PROCTRACE
			if(i_state){
				printf("psignal(%lx,%u) wake %lx [%s]\n",ptol(event),n,
				 ptol(pp),pp->name);
				fflush(stdout);
			}
#endif /* PROCTRACE */
			delproc(pp);
			pp->state &= ~WAITING;
			pp->event = 0;
			pp->retval = 0;
			addproc(pp);
			n--;
			cnt++;
		}
	}
#endif	/* SUSPEND_PROC */
	restore(i_state);
	return cnt;
}

/* Rename a process */
void
chname(pp,newname)
struct proc *pp;
char *newname;
{
	free(pp->name);
	pp->name = strdup(newname);
}
/* Remove a process entry from the appropriate table */
static void
delproc(entry)
register struct proc *entry;	/* Pointer to entry */
{
	int i_state;

	if(entry == NULLPROC)
		return;

	i_state = dirps();
	if(entry->next != NULLPROC)
		entry->next->prev = entry->prev;
	if(entry->prev != NULLPROC){
		entry->prev->next = entry->next;
	} else {
		switch(entry->state){
		case READY:
			Rdytab = entry->next;
			break;
		case WAITING:
			Waittab[phash(entry->event)] = entry->next;
			break;
#ifdef	SUSPEND_PROC
		case SUSPEND:
		case SUSPEND|WAITING:
			Susptab = entry->next;
			break;
#endif
		}
	}
	restore(i_state);
}
/* Append proc entry to end of appropriate list */
static void
addproc(entry)
register struct proc *entry;	/* Pointer to entry */
{
	register struct proc *pp;
	struct proc **head;
	int i_state;

	if(entry == NULLPROC)
		return;

	switch(entry->state){
	case READY:
		head = &Rdytab;
		break;
	case WAITING:
		head = &Waittab[phash(entry->event)];
		break;
#ifdef	SUSPEND_PROC
	case SUSPEND:
	case SUSPEND|WAITING:
		head = &Susptab;
		break;
#endif
	}
	entry->next = NULLPROC;
	i_state = dirps();
	if(*head == NULLPROC){
		/* Empty list, stick at beginning */
		entry->prev = NULLPROC;
		*head = entry;
	} else {
		/* Find last entry on list */
		for(pp = *head;pp->next != NULLPROC;pp = pp->next)
			;
		pp->next = entry;
		entry->prev = pp;
	}
	restore(i_state);
}