ports//devel/libcii/work/src/thread.c

static char rcsid[] = "$Id: H:/drh/idioms/book/RCS/thread.doc,v 1.11 1997/02/21 19:50:51 drh Exp $";
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include </usr/include/signal.h>
#include <sys/time.h>
#include "assert.h"
#include "mem.h"
#include "thread.h"
#include "sem.h"
void _MONITOR(void) {}
extern void _ENDMONITOR(void);
#define T Thread_T
#define isempty(q) ((q) == NULL)
struct T {
	unsigned long *sp;						/* must be first */
	T link;
	T *inqueue;
	T handle;
	Except_Frame *estack;
	int code;
	T join;
	T next;
	int alerted;
};
static T ready = NULL;
static T current;
static int nthreads;
static struct Thread_T root;
static T join0;
static T freelist;
const Except_T Thread_Alerted = { "Thread alerted" };
const Except_T Thread_Failed =
	{ "Thread creation failed" };
static int critical;
extern void _swtch(T from, T to);
static void put(T t, T *q) {
	assert(t);
	assert(t->inqueue == NULL && t->link == NULL);
	if (*q) {
		t->link = (*q)->link;
		(*q)->link = t;
	} else
		t->link = t;
	*q = t;
	t->inqueue = q;
}
static T get(T *q) {
	T t;
	assert(!isempty(*q));
	t = (*q)->link;
	if (t == *q)
		*q = NULL;
	else
		(*q)->link = t->link;
	assert(t->inqueue == q);
	t->link = NULL;
	t->inqueue = NULL;
	return t;
}
static void delete(T t, T *q) {
	T p;
	assert(t->link && t->inqueue == q);
	assert(!isempty(*q));
	for (p = *q; p->link != t; p = p->link)
		;
	if (p == t)
		*q = NULL;
	else {
		p->link = t->link;
		if (*q == t)
			*q = p;
	}
	t->link = NULL;
	t->inqueue = NULL;
}
static void run(void) {
	T t = current;
	current = get(&ready);
	t->estack = Except_stack;
	Except_stack = current->estack;
	_swtch(t, current);
}
static void testalert(void) {
	if (current->alerted) {
		current->alerted = 0;
		RAISE(Thread_Alerted);
	}
}
static void release(void) {
	T t;
	do { critical++;
	while ((t = freelist) != NULL) {
		freelist = t->next;
		FREE(t);
	}
	critical--; } while (0);
}
#if linux
#include <asm/sigcontext.h>
static int interrupt(int sig, struct sigcontext_struct sc) {
	if (critical ||
	   sc.eip >= (unsigned long)_MONITOR
	&& sc.eip <= (unsigned long)_ENDMONITOR)
		return 0;
	put(current, &ready);
	do { critical++;
	sigsetmask(sc.oldmask);
	critical--; } while (0);
	run();
	return 0;
}
#else
static int interrupt(int sig, int code,
	struct sigcontext *scp) {
	if (critical ||
	   scp->sc_pc >= (unsigned long)_MONITOR
	&& scp->sc_pc <= (unsigned long)_ENDMONITOR)
		return 0;
	put(current, &ready);
	sigprocmask(SIG_SETMASK, NULL, &(scp->sc_mask));
	run();
	return 0;
}
#endif
int Thread_init(int preempt, ...) {
	assert(preempt == 0 || preempt == 1);
	assert(current == NULL);
	root.handle = &root;
	current = &root;
	nthreads = 1;
	if (preempt) {
		{
			struct sigaction sa;
			memset(&sa, '\0', sizeof sa);
			sa.sa_handler = (void (*)())interrupt;
			if (sigaction(SIGVTALRM, &sa, NULL) < 0)
				return 0;
		}
		{
			struct itimerval it;
			it.it_value.tv_sec     =  0;
			it.it_value.tv_usec    = 50;
			it.it_interval.tv_sec  =  0;
			it.it_interval.tv_usec = 50;
			if (setitimer(ITIMER_VIRTUAL, &it, NULL) < 0)
				return 0;
		}
	}
	return 1;
}
T Thread_self(void) {
	assert(current);
	return current;
}
void Thread_pause(void) {
	assert(current);
	put(current, &ready);
	run();
}
int Thread_join(T t) {
	assert(current && t != current);
	testalert();
	if (t) {
		if (t->handle == t) {
			put(current, &t->join);
			run();
			testalert();
			return current->code;
		} else
			return -1;
	} else {
		assert(isempty(join0));
		if (nthreads > 1) {
			put(current, &join0);
			run();
			testalert();
		}
		return 0;
	}
}
void Thread_exit(int code) {
	assert(current);
	release();
	if (current != &root) {
		current->next = freelist;
		freelist = current;
	}
	current->handle = NULL;
	while (!isempty(current->join)) {
		T t = get(&current->join);
		t->code = code;
		put(t, &ready);
	}
	if (!isempty(join0) && nthreads == 2) {
		assert(isempty(ready));
		put(get(&join0), &ready);
	}
	if (--nthreads == 0)
		exit(code);
	else
		run();
}
void Thread_alert(T t) {
	assert(current);
	assert(t && t->handle == t);
	t->alerted = 1;
	if (t->inqueue) {
		delete(t, t->inqueue);
		put(t, &ready);
	}
}
T Thread_new(int apply(void *), void *args,
	int nbytes, ...) {
 	T t;
	assert(current);
	assert(apply);
	assert(args && nbytes >= 0 || args == NULL);
	if (args == NULL)
		nbytes = 0;
	{
		int stacksize = (16*1024+sizeof (*t)+nbytes+15)&~15;
		release();
		do { critical++;
		TRY
			t = ALLOC(stacksize);
			memset(t, '\0', sizeof *t);
		EXCEPT(Mem_Failed)
			t = NULL;
		END_TRY;
		critical--; } while (0);
		if (t == NULL)
			RAISE(Thread_Failed);
		t->sp = (void *)((char *)t + stacksize);
		while (((unsigned long)t->sp)&15)
			t->sp--;
	}
	t->handle = t;
	if (nbytes > 0) {
		t->sp -= ((nbytes + 15U)&~15)/sizeof (*t->sp);
		do { critical++;
		memcpy(t->sp, args, nbytes);
		critical--; } while (0);
		args = t->sp;
	}
#if __alpha
	{ extern void _thrstart(void);
	  t->sp -= 112/8;
	  t->sp[(48+24)/8] = (unsigned long)Thread_exit;
	  t->sp[(48+16)/8] = (unsigned long)args;
	  t->sp[(48+ 8)/8] = (unsigned long)apply;
	  t->sp[(48+ 0)/8] = (unsigned long)_thrstart; }
#elif mips
	{ extern void _start(void);
	  t->sp -= 16/4;
	  t->sp -= 88/4;
	  t->sp[(48+20)/4] = (unsigned long)Thread_exit;
	  t->sp[(48+28)/4] = (unsigned long)args;
	  t->sp[(48+32)/4] = (unsigned long)apply;
	  t->sp[(48+36)/4] = (unsigned long)_start; }
#elif sparc
	{ 	int i; void *fp; extern void _start(void);
	  	for (i = 0; i < 8; i++)
	  		*--t->sp = 0;
	  	*--t->sp = (unsigned long)args;
	  	*--t->sp = (unsigned long)apply;
	  	t->sp -= 64/4;
	  	fp = t->sp;
	  	*--t->sp = (unsigned long)_start - 8;
	  	*--t->sp = (unsigned long)fp;
	  	t->sp -= 64/4; }
#elif (linux || unix) && i386
	{ extern void _thrstart(void);
	  t->sp -= 4/4;
	  *t->sp = (unsigned long)_thrstart;
	  t->sp -= 16/4;
	  t->sp[4/4]  = (unsigned long)apply;
	  t->sp[8/4]  = (unsigned long)args;
	  t->sp[12/4] = (unsigned long)t->sp + (4+16)/4; }
#else
	Unsupported platform
#endif
	nthreads++;
	put(t, &ready);
	return t;
}
#undef T
#define T Sem_T
T *Sem_new(int count) {
	T *s;
	NEW(s);
	Sem_init(s, count);
	return s;
}
void Sem_init(T *s, int count) {
	assert(current);
	assert(s);
	s->count = count;
	s->queue = NULL;
}
void Sem_wait(T *s) {
	assert(current);
	assert(s);
	testalert();
	if (s->count <= 0) {
		put(current, (Thread_T *)&s->queue);
		run();
		testalert();
	} else
		--s->count;
}
void Sem_signal(T *s) {
	assert(current);
	assert(s);
	if (s->count == 0 && !isempty(s->queue)) {
		Thread_T t = get((Thread_T *)&s->queue);
		assert(!t->alerted);
		put(t, &ready);
	} else
		++s->count;
}
#undef T
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