Changes in the user space code of the optimistic semaphores.
Unused semaphore stats have been removed. ACs use spin locks
with no backoff. The other roles use the standard locks.

Reference: /n/patches.lsub.org/patch/upsemstats
Date: Mon Jun 25 20:29:16 CES 2012
Signed-off-by: esoriano@lsub.org

--- /sys/src/libc/9sys/upsem.c	Fri Jun  8 11:35:52 2012
+++ /sys/src/libc/9sys/upsem.c	Mon Jun 25 19:18:31 2012
@@ -4,10 +4,6 @@
 typedef struct Cnt Cnt;	/* debug */
 struct Cnt
 {
-	int	sleep;
-	int	zsleep;
-	int	wake;
-	int	zwake;
 	int	uup;
 	int	kup;
 	int	udown;
@@ -24,25 +20,17 @@
 static Cnt c;
 
 /*
- * The genuine spin lock
+ * For ACs, no backoff
  */
 static void
-_lock(Lock *lk)
+nixaclock(Lock *lk)
 {
 	while(_tas(&lk->val))
-		;
+		while(lk->val)
+			;
 	return;
 }
 
-static void
-_yield(void)
-{
-	int nixtype;
-
-	getcoreno(&nixtype);
-	if(nixtype != NIXAC)
-		sleep(0);
-}
 
 void
 initsem(Sem *s, int val)
@@ -55,10 +43,17 @@
 void
 upsem(Sem *s)
 {
+	int nixtype;
 
 	assert(s != nil);
-	
-	_lock(s);
+
+	getcoreno(&nixtype);
+
+	if(nixtype == NIXAC)	
+		nixaclock(s); 
+	else 
+		lock(s); 
+
 	if(s->tickets == 0 && (s->waiting > 0 || s->going > 0)){
 		unlock(s);
 		ainc(&c.kup);
@@ -74,14 +69,20 @@
 downsem(Sem *s, int block)
 {
 	int i;
+	int nixtype;
 
 	assert(s != nil);
+	getcoreno(&nixtype);
 
 	/* busy wait */
 	for(i = 0; s->tickets == 0 && i < semtrytimes; i++)
 		;
 
-	_lock(s);
+	if(nixtype == NIXAC)	
+		nixaclock(s); 
+	else 
+		lock(s); 
+
 	if(! block && s->tickets == 0){
 		unlock(s);
 		return 0;
@@ -100,7 +101,6 @@
 	return 1;
 }
 
-
 /*
  * No optimistic for now.
  */
@@ -134,10 +134,6 @@
 void
 semstats(void)
 {
-	print("sleep: %d\n", c.sleep);
-	print("zsleep: %d\n", c.zsleep);
-	print("wake: %d\n", c.wake);
-	print("zwake: %d\n", c.zwake);
 	print("uup: %d\n", c.uup);
 	print("kup: %d\n", c.kup);
 	print("udown: %d\n", c.udown);