/* $Header: lwp.c,v 1.2 87/09/01 11:13:05 nichols Exp $ */
/* $Source: /afs/andrew.cmu.edu/usr7/kazar/afs/lwp/RCS/lwp.c,v $ */

#ifndef lint
static char *rcsid = "$Header: lwp.c,v 1.2 87/09/01 11:13:05 nichols Exp $";
#endif

/*
 * P_R_P_Q_# (C) COPYRIGHT IBM CORPORATION 1987
 * LICENSED MATERIALS - PROPERTY OF IBM
 * REFER TO COPYRIGHT INSTRUCTIONS FORM NUMBER G120-2083
 */

/*******************************************************************\
* 								    *
* 	Information Technology Center				    *
* 	Carnegie-Mellon University				    *
* 								    *
* 								    *
\*******************************************************************/


/* allocate externs here */
#define  LWP_KERNEL
#define  NULL	    0

#include "lwp.h"

extern char PRE_Block;	/* from preempt.c */

#define  ON	    1
#define  OFF	    0
#define  TRUE	    1
#define  FALSE	    0
#define  READY		2
#define  WAITING		3
#define  DESTROYED	4
#define QWAITING		5
#define  MAXINT     (~(1<<((sizeof(int)*8)-1)))
#define  MINSTACK   44

/* Debugging macro */
#ifdef DEBUG
#define Debug(level, msg)\
	 if (lwp_debug && lwp_debug >= level) {\
	     printf("***LWP (0x%x): ", lwp_cpptr);\
	     printf msg;\
	     putchar('\n');\
	 }

#else
#define Debug(level, msg)

#endif

int	 Dispatcher();
int	 Create_Process_Part2();
int	 Exit_LWP();
long	 Initialize_Stack();
int	 Stack_Used();
char   (*RC_to_ASCII());

#define MAX_PRIORITIES	(LWP_MAX_PRIORITY+1)

struct QUEUE {
    PROCESS	head;
    int		count;
} runnable[MAX_PRIORITIES], blocked;
/* Invariant for runnable queues: The head of each queue points to the currently running process if it is in that queue, or it points to the next process in that queue that should run. */

/* Offset of stack field within pcb -- used by stack checking stuff */
int stack_offset;

/* Stack checking action */
int lwp_overflowAction = LWP_SOABORT;

/* Controls stack size counting. */
int lwp_stackUseEnabled = TRUE;	/* pay the price */

static remove(p, q)
    register PROCESS p;
    register struct QUEUE *q;
{
    /* Special test for only element on queue */
    if (q->count == 1)
	q -> head = NULL;
    else {
	/* Not only element, do normal remove */
	p -> next -> prev = p -> prev;
	p -> prev -> next = p -> next;
    }
    /* See if head pointing to this element */
    if (q->head == p) q -> head = p -> next;
    q->count--;
    p -> next = p -> prev = NULL;
}

static insert(p, q)
    register PROCESS p;
    register struct QUEUE *q;
{
    if (q->head == NULL) {	/* Queue is empty */
	q -> head = p;
	p -> next = p -> prev = p;
    } else {			/* Regular insert */
	p -> prev = q -> head -> prev;
	q -> head -> prev -> next = p;
	q -> head -> prev = p;
	p -> next = q -> head;
    }
    q->count++;
}

static move(p, from, to)
    PROCESS p;
    struct QUEUE *from, *to;
{
    remove(p, from);
    insert(p, to);
}

/* Iterator macro */
#define for_all_elts(var, q, body)\
	{\
	    register PROCESS var, _NEXT_;\
	    register int _I_;\
	    for (_I_=q.count, var = q.head; _I_>0; _I_--, var=_NEXT_) {\
		_NEXT_ = var -> next;\
		body\
	    }\
	}

/*									    */
/*****************************************************************************\
* 									      *
*  Following section documents the Assembler interfaces used by LWP code      *
* 									      *
\*****************************************************************************/

/*
	savecontext(int (*ep)(), struct lwp_context *savearea, char *sp);

Stub for Assembler routine that will
save the current SP value in the passed
context savearea and call the function
whose entry point is in ep.  If the sp
parameter is NULL, the current stack is
used, otherwise sp becomes the new stack
pointer.

	returnto(struct lwp_context *savearea);

Stub for Assembler routine that will
restore context from a passed savearea
and return to the restored C frame.

*/

/* Macro to force a re-schedule.  Strange name is historical */

#define Set_LWP_RC(dummy) savecontext(Dispatcher, &lwp_cpptr->context, NULL)

static struct lwp_ctl *lwp_init = 0;

int LWP_QWait()
    {register PROCESS tp;
    (tp=lwp_cpptr) -> status = QWAITING;
    remove(tp, &runnable[tp->priority]);
    Set_LWP_RC();
    return LWP_SUCCESS;
}

int LWP_QSignal(pid)
    register PROCESS pid; {
    if (pid->status == QWAITING) {
	pid->status = READY;
	insert(pid, &runnable[pid->priority]);
	return LWP_SUCCESS;
    }
    else return LWP_ENOWAIT;
}

int LWP_CreateProcess(ep, stacksize, priority, parm, name, pid)
   int   (*ep)();
   int   stacksize, priority;
   char  *parm;
   char  *name;
   PROCESS *pid;
{
    PROCESS temp, temp2;
    char *stackptr;

    Debug(0, ("Entered LWP_CreateProcess"))
    /* Throw away all dead process control blocks */
    purge_dead_pcbs();
    if (lwp_init) {
	temp = (PROCESS) malloc (sizeof (struct lwp_pcb));
	if (temp == NULL) {
	    Set_LWP_RC();
	    return LWP_ENOMEM;
	}
	if (stacksize < MINSTACK)
	    stacksize = 1000;
	else
	    stacksize = 4 * ((stacksize+3) / 4);
	if ((stackptr = (char *) malloc(stacksize)) == NULL) {
	    Set_LWP_RC();
	    return LWP_ENOMEM;
	}
	if (priority < 0 || priority >= MAX_PRIORITIES) {
	    Set_LWP_RC();
	    return LWP_EBADPRI;
	}
 	Initialize_Stack(stackptr, stacksize);
	Initialize_PCB(temp, priority, stackptr, stacksize, ep, parm, name);
	insert(temp, &runnable[priority]);
	temp2 = lwp_cpptr;
	if (PRE_Block != 0) Abort_LWP("PRE_Block not 0");

	/* Gross hack: beware! */
	PRE_Block = 1;
	lwp_cpptr = temp;
	savecontext(Create_Process_Part2, &temp2->context, stackptr+stacksize-4);
	/* End of gross hack */

	Set_LWP_RC();
	*pid = temp;
	return 0;
    } else
	return LWP_EINIT;
}

int LWP_CurrentProcess(pid)	/* returns pid of current process */
    PROCESS *pid;
{
    Debug(0, ("Entered Current_Process"))
    if (lwp_init) {
	    *pid = lwp_cpptr;
	    return LWP_SUCCESS;
    } else
	return LWP_EINIT;
}

#define LWPANCHOR (*lwp_init)

int LWP_DestroyProcess(pid)		/* destroy a lightweight process */
    PROCESS pid;
{
    PROCESS temp;

    Debug(0, ("Entered Destroy_Process"))
    if (lwp_init) {
	if (lwp_cpptr != pid) {
	    Dispose_of_Dead_PCB(pid);
	    Set_LWP_RC();
	} else {
	    pid -> status = DESTROYED;
	    move(pid, &runnable[pid->priority], &blocked);
	    temp = lwp_cpptr;
	    savecontext(Dispatcher, &(temp -> context),
			&(LWPANCHOR.dsptchstack[(sizeof LWPANCHOR.dsptchstack)-4]));
	}
	return LWP_SUCCESS;
    } else
	return LWP_EINIT;
}

int LWP_DispatchProcess()		/* explicit voluntary preemption */
{
    Debug(2, ("Entered Dispatch_Process"))
    if (lwp_init) {
	Set_LWP_RC();
	return LWP_SUCCESS;
    } else
	return LWP_EINIT;
}

#ifdef DEBUG
Dump_Processes()
{
    if (lwp_init) {
	register int i;
	for (i=0; i<MAX_PRIORITIES; i++)
	    for_all_elts(x, runnable[i], {
		printf("[Priority %d]\n", i);
		Dump_One_Process(x);
	    })
	for_all_elts(x, blocked, { Dump_One_Process(x); })
    } else
	printf("***LWP: LWP support not initialized\n");
}
#endif

int LWP_GetProcessPriority(pid, priority)	/* returns process priority */
    PROCESS pid;
    int *priority;
{
    Debug(0, ("Entered Get_Process_Priority"))
    if (lwp_init) {
	*priority = pid -> priority;
	return 0;
    } else
	return LWP_EINIT;
}

int LWP_InitializeProcessSupport(priority, pid)
    int priority;
    PROCESS *pid;
{
    PROCESS temp;
    struct lwp_pcb dummy;
    register int i;

    Debug(0, ("Entered LWP_InitializeProcessSupport"))
    if (lwp_init != NULL) return LWP_SUCCESS;

    /* Set up offset for stack checking -- do this as soon as possible */
    stack_offset = (char *) &dummy.stack - (char *) &dummy;

    if (priority >= MAX_PRIORITIES) return LWP_EBADPRI;
    for (i=0; i<MAX_PRIORITIES; i++) {
	runnable[i].head = NULL;
	runnable[i].count = 0;
    }
    blocked.head = NULL;
    blocked.count = 0;
    lwp_init = (struct lwp_ctl *) malloc(sizeof(struct lwp_ctl));
    temp = (PROCESS) malloc(sizeof(struct lwp_pcb));
    if (lwp_init == NULL || temp == NULL)
	Abort_LWP("Insufficient Storage to Initialize LWP Support");
    LWPANCHOR.processcnt = 1;
    LWPANCHOR.outerpid = temp;
    LWPANCHOR.outersp = NULL;
    Initialize_PCB(temp, priority, NULL, 0, NULL, NULL, "Main Process [created by LWP]");
    insert(temp, &runnable[priority]);
    savecontext(Dispatcher, &temp->context, NULL);
    LWPANCHOR.outersp = temp -> context.topstack;
    Set_LWP_RC();
    *pid = temp;
    return LWP_SUCCESS;
}

int LWP_INTERNALSIGNAL(event, yield)		/* signal the occurence of an event */
    char *event;
    int yield;
{
    Debug(2, ("Entered LWP_SignalProcess"))
    if (lwp_init) {
	int rc;
	rc = Internal_Signal(event);
	if (yield) Set_LWP_RC();
	return rc;
    } else
	return LWP_EINIT;
}

int LWP_TerminateProcessSupport()	/* terminate all LWP support */
{
    register int i;

    Debug(0, ("Entered Terminate_Process_Support"))
    if (lwp_init == NULL) return LWP_EINIT;
    if (lwp_cpptr != LWPANCHOR.outerpid)
	Abort_LWP("Terminate_Process_Support invoked from wrong process!");
    for (i=0; i<MAX_PRIORITIES; i++)
	for_all_elts(cur, runnable[i], { Free_PCB(cur); })
    for_all_elts(cur, blocked, { Free_PCB(cur); })
    free(lwp_init);
    lwp_init = NULL;
    return LWP_SUCCESS;
}

int LWP_WaitProcess(event)		/* wait on a single event */
    char *event;
{
    char *tempev[2];

    Debug(2, ("Entered Wait_Process"))
    if (event == NULL) return LWP_EBADEVENT;
    tempev[0] = event;
    tempev[1] = NULL;
    return LWP_MwaitProcess(1, tempev);
}

int LWP_MwaitProcess(wcount, evlist)	/* wait on m of n events */
    int wcount;
    char *evlist[];
{
    register int ecount, i;

    Debug(0, ("Entered Mwait_Process [waitcnt = %d]", wcount))

    if (evlist == NULL) {
	Set_LWP_RC();
	return LWP_EBADCOUNT;
    }
    for (ecount = 0; evlist[ecount] != NULL; ecount++) ;
    if (ecount == 0) {
	Set_LWP_RC();
	return LWP_EBADCOUNT;
    }
    if (lwp_init) {
	if (wcount>ecount || wcount<0) {
	    Set_LWP_RC();
	    return LWP_EBADCOUNT;
	}
	if (ecount > lwp_cpptr->eventlistsize) {
	    lwp_cpptr->eventlist = (char **)realloc(lwp_cpptr->eventlist, ecount*sizeof(char *));
	    lwp_cpptr->eventlistsize = ecount;
	}
	for (i=0; i<ecount; i++) lwp_cpptr -> eventlist[i] = evlist[i];
	if (wcount > 0) {
	    lwp_cpptr -> status = WAITING;
	    move(lwp_cpptr, &runnable[lwp_cpptr->priority], &blocked);
	}
	lwp_cpptr -> wakevent = 0;
	lwp_cpptr -> waitcnt = wcount;
	lwp_cpptr -> eventcnt = ecount;
	Set_LWP_RC();
	return LWP_SUCCESS;
    }
    return LWP_EINIT;
}

int LWP_StackUsed(pid, max, used)
    PROCESS pid;
    int *max, *used;
{
    *max = pid -> stacksize;
    *used = Stack_Used(pid->stack, *max);
    if (*used == 0)
	return LWP_NO_STACK;
    return LWP_SUCCESS;
}

/*
 *  The following functions are strictly
 *  INTERNAL to the LWP support package.
 */

static Abort_LWP(msg)
    char *msg;
{
    struct lwp_context tempcontext;

    Debug(0, ("Entered Abort_LWP"))
    printf("***LWP: %s\n",msg);
    printf("***LWP: Abort --- dumping PCBs ...\n");
#ifdef DEBUG
    Dump_Processes();
#endif
    if (LWPANCHOR.outersp == NULL)
	Exit_LWP();
    else
	savecontext(Exit_LWP, &tempcontext, LWPANCHOR.outersp);
}

static Create_Process_Part2 ()	/* creates a context for the new process */
{
    PROCESS temp;

    Debug(2, ("Entered Create_Process_Part2"))
    temp = lwp_cpptr;		/* Get current process id */
    savecontext(Dispatcher, &temp->context, NULL);
    (*temp->ep)(temp->parm);
    LWP_DestroyProcess(temp);
}

static Delete_PCB(pid) 	/* remove a PCB from the process list */
    register PROCESS pid;
{
    Debug(4, ("Entered Delete_PCB"))
    remove(pid, (pid->blockflag || pid->status==WAITING || pid->status==DESTROYED
		 ? &blocked
		 : &runnable[pid->priority]));
    LWPANCHOR.processcnt--;
}

#ifdef DEBUG
static Dump_One_Process(pid)
   PROCESS pid;
{
    int i;

    printf("***LWP: Process Control Block at 0x%x\n", pid);
    printf("***LWP: Name: %s\n", pid->name);
    if (pid->ep != NULL)
	printf("***LWP: Initial entry point: 0x%x\n", pid->ep);
    if (pid->blockflag) printf("BLOCKED and ");
    switch (pid->status) {
	case READY:	printf("READY");     break;
	case WAITING:	printf("WAITING");   break;
	case DESTROYED:	printf("DESTROYED"); break;
	default:	printf("unknown");
    }
    putchar('\n');
    printf("***LWP: Priority: %d \tInitial parameter: 0x%x\n",
	    pid->priority, pid->parm);
    if (pid->stacksize != 0) {
	printf("***LWP:  Stacksize: %d \tStack base address: 0x%x\n",
		pid->stacksize, pid->stack);
	printf("***LWP: HWM stack usage: ");
	printf("%d\n", Stack_Used(pid->stack,pid->stacksize));
	free (pid->stack);
    }
    printf("***LWP: Current Stack Pointer: 0x%x\n", pid->context.topstack);
    if (pid->eventcnt > 0) {
	printf("***LWP: Number of events outstanding: %d\n", pid->waitcnt);
	printf("***LWP: Event id list:");
	for (i=0;i<pid->eventcnt;i++)
	    printf(" 0x%x", pid->eventlist[i]);
	putchar('\n');
    }
    if (pid->wakevent>0)
	printf("***LWP: Number of last wakeup event: %d\n", pid->wakevent);
}
#endif

static purge_dead_pcbs()
{
    for_all_elts(cur, blocked, { if (cur->status == DESTROYED) Dispose_of_Dead_PCB(cur); })
}

int LWP_TraceProcesses = 0;

static Dispatcher()		/* Lightweight process dispatcher */
{
    register int i;
#ifdef DEBUG
    static int dispatch_count = 0;

    if (LWP_TraceProcesses > 0) {
	for (i=0; i<MAX_PRIORITIES; i++) {
	    printf("[Priority %d, runnable (%d):", i, runnable[i].count);
	    for_all_elts(p, runnable[i], {
		printf(" \"%s\"", p->name);
	    })
	    puts("]");
	}
	printf("[Blocked (%d):", blocked.count);
	for_all_elts(p, blocked, {
	    printf(" \"%s\"", p->name);
	})
	puts("]");
    }
#endif

    /* Check for stack overflowif this lwp has a stack.  Check for
       the guard word at the front of the stack being damaged and
       for the stack pointer being below the front of the stack.
       WARNING!  This code assumes that stacks grow downward. */
    if (lwp_cpptr != NULL && lwp_cpptr->stack != NULL
	    && (lwp_cpptr->stackcheck != *(long *)(lwp_cpptr->stack)
		|| lwp_cpptr->context.topstack < lwp_cpptr->stack)) {
	switch (lwp_overflowAction) {
	    case LWP_SOQUIET:
		break;
	    case LWP_SOABORT:
		Overflow_Complain();
		abort ();
	    case LWP_SOMESSAGE:
	    default:
		Overflow_Complain();
		lwp_overflowAction = LWP_SOQUIET;
		break;
	}
    }

    /* Move head of current runnable queue forward if current LWP is still in it. */
    if (lwp_cpptr != NULL && lwp_cpptr == runnable[lwp_cpptr->priority].head)
	runnable[lwp_cpptr->priority].head = runnable[lwp_cpptr->priority].head -> next;
    /* Find highest priority with runnable processes. */
    for (i=MAX_PRIORITIES-1; i>=0; i--)
	if (runnable[i].head != NULL) break;

    if (i < 0) Abort_LWP("No READY processes");

#ifdef DEBUG
    if (LWP_TraceProcesses > 0)
	printf("Dispatch %d [PCB at 0x%x] \"%s\"\n", ++dispatch_count, runnable[i].head, runnable[i].head->name);
#endif
    if (PRE_Block != 1) Abort_LWP("PRE_Block not 1");
    lwp_cpptr = runnable[i].head;
    returnto(&lwp_cpptr->context);
}

/* Complain of a stack overflow to stderr without using stdio. */
static Overflow_Complain ()
{
    char *msg1 = "LWP: stack overflow in process ";
    char *msg2 = "!\n";

    write (2, msg1, strlen(msg1));
    write (2, lwp_cpptr->name, strlen(lwp_cpptr->name));
    write (2, msg2, strlen(msg2));
}

static Dispose_of_Dead_PCB (cur)
    PROCESS cur;
{
    Debug(4, ("Entered Dispose_of_Dead_PCB"))
    Delete_PCB(cur);
    Free_PCB(cur);
/*
    Internal_Signal(cur);
*/
}

static Exit_LWP()
{
    abort();
}

static Free_PCB(pid)
    PROCESS pid;
{
    Debug(4, ("Entered Free_PCB"))
    if (pid -> stack != NULL) {
	Debug(0, ("HWM stack usage: %d, [PCB at 0x%x]",
		   Stack_Used(pid->stack,pid->stacksize), pid))
	free(pid -> stack);
    }
    if (pid->eventlist != NULL)  free(pid->eventlist);
    free(pid);
}

static Initialize_PCB(temp, priority, stack, stacksize, ep, parm, name)
    PROCESS temp;
    int	(*ep)();
    int	stacksize, priority;
    char *parm;
    char *name,*stack;
{
    register int i = 0;

    Debug(4, ("Entered Initialize_PCB"))
    if (name != NULL)
	while (((temp -> name[i] = name[i]) != '\0') && (i < 31)) i++;
    temp -> name[31] = '\0';
    temp -> status = READY;
    temp -> eventlist = (char **)malloc(EVINITSIZE*sizeof(char *));
    temp -> eventlistsize = EVINITSIZE;
    temp -> eventcnt = 0;
    temp -> wakevent = 0;
    temp -> waitcnt = 0;
    temp -> blockflag = 0;
    temp -> iomgrRequest = 0;
    temp -> priority = priority;
    temp -> index = lwp_nextindex++;
    temp -> stack = stack;
    temp -> stacksize = stacksize;
    if (temp -> stack != NULL)
	temp -> stackcheck = *(long *) (temp -> stack);
    temp -> ep = ep;
    temp -> parm = parm;
    temp -> misc = NULL;	/* currently unused */
    temp -> next = NULL;
    temp -> prev = NULL;
    temp -> rused = NULL;
    temp -> level = 1;		/* non-preemptable */
}

static int Internal_Signal(event)
    register char *event;
{
    int rc = LWP_ENOWAIT;
    register int i;

    Debug(0, ("Entered Internal_Signal [event id 0x%x]", event))
    if (!lwp_init) return LWP_EINIT;
    if (event == NULL) return LWP_EBADEVENT;
    for_all_elts(temp, blocked, {
	if (temp->status == WAITING)
	    for (i=0; i < temp->eventcnt; i++) {
		if (temp -> eventlist[i] == event) {
		    temp -> eventlist[i] = NULL;
		    rc = LWP_SUCCESS;
		    Debug(0, ("Signal satisfied for PCB 0x%x", temp))
		    if (--temp->waitcnt == 0) {
			temp -> status = READY;
			temp -> wakevent = i+1;
			move(temp, &blocked, &runnable[temp->priority]);
			break;
		    }
		}
	    }
    })
    return rc;
}

/* This can be any unlikely pattern except 0x00010203 or the reverse. */
#define STACKMAGIC	0xBADBADBA
static long Initialize_Stack(stackptr, stacksize)
    char *stackptr;
    int stacksize;
{
    register int i;

    Debug(4, ("Entered Initialize_Stack"))
    if (lwp_stackUseEnabled)
	for (i=0; i<stacksize; i++)
	    stackptr[i] = i &0xff;
    else
	*(long *)stackptr = STACKMAGIC;
}

static int Stack_Used(stackptr, stacksize)
   register char *stackptr;
   int stacksize;
{
    register int    i;

    if (*(long *) stackptr == STACKMAGIC)
	return 0;
    else {
	for (i = 0; i < stacksize; i++)
	    if ((unsigned char) stackptr[i] != (i & 0xff))
		return (stacksize - i);
	return 0;
    }
}


LWP_NewRock(Tag, Value)
    int Tag;		/* IN */
    char *Value;	/* IN */
    /* Finds a free rock and sets its value to Value.
	Return codes:
		LWP_SUCCESS	Rock did not exist and a new one was used
		LWP_EBADROCK	Rock already exists.
		LWP_ENOROCKS	All rocks are in use.

	From the above semantics, you can only set a rock value once.  This is specifically
	to prevent multiple users of the LWP package from accidentally using the same Tag
	value and clobbering others.  You can always use one level of indirection to obtain
	a rock whose contents can change.
    */
    {
    register int i;
    register struct rock *ra;	/* rock array */
    
    ra = lwp_cpptr->rlist;

    for (i = 0; i < lwp_cpptr->rused; i++)
	if (ra[i].tag == Tag) return(LWP_EBADROCK);

    if (lwp_cpptr->rused < MAXROCKS)
	{
	ra[lwp_cpptr->rused].tag = Tag;
	ra[lwp_cpptr->rused].value = Value;
	lwp_cpptr->rused++;
	return(LWP_SUCCESS);
	}
    else return(LWP_ENOROCKS);
    }


LWP_GetRock(Tag,  Value)
    int Tag;		/* IN */
    char **Value;	/* OUT */
    
    /* Obtains the pointer Value associated with the rock Tag of this LWP.
       Returns:
	    LWP_SUCCESS		if specified rock exists and Value has been filled
	    LWP_EBADROCK	rock specified does not exist
    */
    {
    register int i;
    register struct rock *ra;
    
    ra = lwp_cpptr->rlist;
    
    for (i = 0; i < lwp_cpptr->rused; i++)
	if (ra[i].tag == Tag)
	    {
	    *Value =  ra[i].value;
	    return(LWP_SUCCESS);
	    }
    return(LWP_EBADROCK);
    }