Import sources from 2011-03-30 iso image

1 files changed, 363 insertions, 0 deletions

diff --git a/sys/src/libc/9sys/qlock.c b/sys/src/libc/9sys/qlock.c
new file mode 100755
index 000000000..fb2d80238
--- /dev/null
+++ b/sys/src/libc/9sys/qlock.c
@@ -0,0 +1,363 @@
+#include <u.h>
+#include <libc.h>
+
+static struct {
+	QLp	*p;
+	QLp	x[1024];
+} ql = {
+	ql.x
+};
+
+enum
+{
+	Queuing,
+	QueuingR,
+	QueuingW,
+	Sleeping,
+};
+
+static void*	(*_rendezvousp)(void*, void*) = rendezvous;
+
+/* this gets called by the thread library ONLY to get us to use its rendezvous */
+void
+_qlockinit(void* (*r)(void*, void*))
+{
+	_rendezvousp = r;
+}
+
+/* find a free shared memory location to queue ourselves in */
+static QLp*
+getqlp(void)
+{
+	QLp *p, *op;
+
+	op = ql.p;
+	for(p = op+1; ; p++){
+		if(p == &ql.x[nelem(ql.x)])
+			p = ql.x;
+		if(p == op)
+			abort();
+		if(_tas(&(p->inuse)) == 0){
+			ql.p = p;
+			p->next = nil;
+			break;
+		}
+	}
+	return p;
+}
+
+void
+qlock(QLock *q)
+{
+	QLp *p, *mp;
+
+	lock(&q->lock);
+	if(!q->locked){
+		q->locked = 1;
+		unlock(&q->lock);
+		return;
+	}
+
+
+	/* chain into waiting list */
+	mp = getqlp();
+	p = q->tail;
+	if(p == nil)
+		q->head = mp;
+	else
+		p->next = mp;
+	q->tail = mp;
+	mp->state = Queuing;
+	unlock(&q->lock);
+
+	/* wait */
+	while((*_rendezvousp)(mp, (void*)1) == (void*)~0)
+		;
+	mp->inuse = 0;
+}
+
+void
+qunlock(QLock *q)
+{
+	QLp *p;
+
+	lock(&q->lock);
+	if (q->locked == 0)
+		fprint(2, "qunlock called with qlock not held, from %#p\n",
+			getcallerpc(&q));
+	p = q->head;
+	if(p != nil){
+		/* wakeup head waiting process */
+		q->head = p->next;
+		if(q->head == nil)
+			q->tail = nil;
+		unlock(&q->lock);
+		while((*_rendezvousp)(p, (void*)0x12345) == (void*)~0)
+			;
+		return;
+	}
+	q->locked = 0;
+	unlock(&q->lock);
+}
+
+int
+canqlock(QLock *q)
+{
+	if(!canlock(&q->lock))
+		return 0;
+	if(!q->locked){
+		q->locked = 1;
+		unlock(&q->lock);
+		return 1;
+	}
+	unlock(&q->lock);
+	return 0;
+}
+
+void
+rlock(RWLock *q)
+{
+	QLp *p, *mp;
+
+	lock(&q->lock);
+	if(q->writer == 0 && q->head == nil){
+		/* no writer, go for it */
+		q->readers++;
+		unlock(&q->lock);
+		return;
+	}
+
+	mp = getqlp();
+	p = q->tail;
+	if(p == 0)
+		q->head = mp;
+	else
+		p->next = mp;
+	q->tail = mp;
+	mp->next = nil;
+	mp->state = QueuingR;
+	unlock(&q->lock);
+
+	/* wait in kernel */
+	while((*_rendezvousp)(mp, (void*)1) == (void*)~0)
+		;
+	mp->inuse = 0;
+}
+
+int
+canrlock(RWLock *q)
+{
+	lock(&q->lock);
+	if (q->writer == 0 && q->head == nil) {
+		/* no writer; go for it */
+		q->readers++;
+		unlock(&q->lock);
+		return 1;
+	}
+	unlock(&q->lock);
+	return 0;
+}
+
+void
+runlock(RWLock *q)
+{
+	QLp *p;
+
+	lock(&q->lock);
+	if(q->readers <= 0)
+		abort();
+	p = q->head;
+	if(--(q->readers) > 0 || p == nil){
+		unlock(&q->lock);
+		return;
+	}
+
+	/* start waiting writer */
+	if(p->state != QueuingW)
+		abort();
+	q->head = p->next;
+	if(q->head == 0)
+		q->tail = 0;
+	q->writer = 1;
+	unlock(&q->lock);
+
+	/* wakeup waiter */
+	while((*_rendezvousp)(p, 0) == (void*)~0)
+		;
+}
+
+void
+wlock(RWLock *q)
+{
+	QLp *p, *mp;
+
+	lock(&q->lock);
+	if(q->readers == 0 && q->writer == 0){
+		/* noone waiting, go for it */
+		q->writer = 1;
+		unlock(&q->lock);
+		return;
+	}
+
+	/* wait */
+	p = q->tail;
+	mp = getqlp();
+	if(p == nil)
+		q->head = mp;
+	else
+		p->next = mp;
+	q->tail = mp;
+	mp->next = nil;
+	mp->state = QueuingW;
+	unlock(&q->lock);
+
+	/* wait in kernel */
+	while((*_rendezvousp)(mp, (void*)1) == (void*)~0)
+		;
+	mp->inuse = 0;
+}
+
+int
+canwlock(RWLock *q)
+{
+	lock(&q->lock);
+	if (q->readers == 0 && q->writer == 0) {
+		/* no one waiting; go for it */
+		q->writer = 1;
+		unlock(&q->lock);
+		return 1;
+	}
+	unlock(&q->lock);
+	return 0;
+}
+
+void
+wunlock(RWLock *q)
+{
+	QLp *p;
+
+	lock(&q->lock);
+	if(q->writer == 0)
+		abort();
+	p = q->head;
+	if(p == nil){
+		q->writer = 0;
+		unlock(&q->lock);
+		return;
+	}
+	if(p->state == QueuingW){
+		/* start waiting writer */
+		q->head = p->next;
+		if(q->head == nil)
+			q->tail = nil;
+		unlock(&q->lock);
+		while((*_rendezvousp)(p, 0) == (void*)~0)
+			;
+		return;
+	}
+
+	if(p->state != QueuingR)
+		abort();
+
+	/* wake waiting readers */
+	while(q->head != nil && q->head->state == QueuingR){
+		p = q->head;
+		q->head = p->next;
+		q->readers++;
+		while((*_rendezvousp)(p, 0) == (void*)~0)
+			;
+	}
+	if(q->head == nil)
+		q->tail = nil;
+	q->writer = 0;
+	unlock(&q->lock);
+}
+
+void
+rsleep(Rendez *r)
+{
+	QLp *t, *me;
+
+	if(!r->l)
+		abort();
+	lock(&r->l->lock);
+	/* we should hold the qlock */
+	if(!r->l->locked)
+		abort();
+
+	/* add ourselves to the wait list */
+	me = getqlp();
+	me->state = Sleeping;
+	if(r->head == nil)
+		r->head = me;
+	else
+		r->tail->next = me;
+	me->next = nil;
+	r->tail = me;
+
+	/* pass the qlock to the next guy */
+	t = r->l->head;
+	if(t){
+		r->l->head = t->next;
+		if(r->l->head == nil)
+			r->l->tail = nil;
+		unlock(&r->l->lock);
+		while((*_rendezvousp)(t, (void*)0x12345) == (void*)~0)
+			;
+	}else{
+		r->l->locked = 0;
+		unlock(&r->l->lock);
+	}
+
+	/* wait for a wakeup */
+	while((*_rendezvousp)(me, (void*)1) == (void*)~0)
+		;
+	me->inuse = 0;
+}
+
+int
+rwakeup(Rendez *r)
+{
+	QLp *t;
+
+	/*
+	 * take off wait and put on front of queue
+	 * put on front so guys that have been waiting will not get starved
+	 */
+	
+	if(!r->l)
+		abort();
+	lock(&r->l->lock);
+	if(!r->l->locked)
+		abort();
+
+	t = r->head;
+	if(t == nil){
+		unlock(&r->l->lock);
+		return 0;
+	}
+
+	r->head = t->next;
+	if(r->head == nil)
+		r->tail = nil;
+
+	t->next = r->l->head;
+	r->l->head = t;
+	if(r->l->tail == nil)
+		r->l->tail = t;
+
+	t->state = Queuing;
+	unlock(&r->l->lock);
+	return 1;
+}
+
+int
+rwakeupall(Rendez *r)
+{
+	int i;
+
+	for(i=0; rwakeup(r); i++)
+		;
+	return i;
+}
+