1 files changed, 141 insertions, 0 deletions
diff --git a/lib9/lock.c b/lib9/lock.c
new file mode 100644
index 00000000..48b5d8c2
--- /dev/null
+++ b/lib9/lock.c
@@ -0,0 +1,141 @@
+#include	"dat.h"
+#include	"fns.h"
+#include	"error.h"
+
+void
+lock(Lock *l)
+{
+	int i;
+
+	if(_tas(&l->val) == 0)
+		return;
+	for(i=0; i<100; i++){
+		if(_tas(&l->val) == 0)
+			return;
+		osyield();
+	}
+	for(i=1;; i++){
+		if(_tas(&l->val) == 0)
+			return;
+		osmillisleep(i*10);
+		if(i > 100){
+			osyield();
+			i = 1;
+		}
+	}
+}
+
+int
+canlock(Lock *l)
+{
+	return _tas(&l->val) == 0;
+}
+
+void
+unlock(Lock *l)
+{
+	l->val = 0;
+}
+
+void
+qlock(QLock *q)
+{
+	Proc *p;
+
+	lock(&q->use);
+	if(!q->locked) {
+		q->locked = 1;
+		unlock(&q->use);
+		return;
+	}
+	p = q->tail;
+	if(p == 0)
+		q->head = up;
+	else
+		p->qnext = up;
+	q->tail = up;
+	up->qnext = 0;
+	unlock(&q->use);
+	osblock();
+}
+
+int
+canqlock(QLock *q)
+{
+	if(!canlock(&q->use))
+		return 0;
+	if(q->locked){
+		unlock(&q->use);
+		return 0;
+	}
+	q->locked = 1;
+	unlock(&q->use);
+	return 1;
+}
+
+void
+qunlock(QLock *q)
+{
+	Proc *p;
+
+	lock(&q->use);
+	p = q->head;
+	if(p) {
+		q->head = p->qnext;
+		if(q->head == 0)
+			q->tail = 0;
+		unlock(&q->use);
+		osready(p);
+		return;
+	}
+	q->locked = 0;
+	unlock(&q->use);
+}
+
+void
+rlock(RWlock *l)
+{
+	qlock(&l->x);		/* wait here for writers and exclusion */
+	lock(&l->l);
+	l->readers++;
+	canqlock(&l->k);	/* block writers if we are the first reader */
+	unlock(&l->l);
+	qunlock(&l->x);
+}
+
+/* same as rlock but punts if there are any writers waiting */
+int
+canrlock(RWlock *l)
+{
+	if (!canqlock(&l->x))
+		return 0;
+	lock(&l->l);
+	l->readers++;
+	canqlock(&l->k);	/* block writers if we are the first reader */
+	unlock(&l->l);
+	qunlock(&l->x);
+	return 1;
+}
+
+void
+runlock(RWlock *l)
+{
+	lock(&l->l);
+	if(--l->readers == 0)	/* last reader out allows writers */
+		qunlock(&l->k);
+	unlock(&l->l);
+}
+
+void
+wlock(RWlock *l)
+{
+	qlock(&l->x);		/* wait here for writers and exclusion */
+	qlock(&l->k);		/* wait here for last reader */
+}
+
+void
+wunlock(RWlock *l)
+{
+	qunlock(&l->k);
+	qunlock(&l->x);
+}