ape: change tas/sleep locks to cas/semacquire/semrelease locks (from sources)

1 files changed, 23 insertions, 14 deletions

diff --git a/sys/src/ape/lib/ap/arm/lock.c b/sys/src/ape/lib/ap/arm/lock.c
index 91c0ba233..65a65df7b 100644
--- a/sys/src/ape/lib/ap/arm/lock.c
+++ b/sys/src/ape/lib/ap/arm/lock.c
@@ -1,26 +1,35 @@
-#define _LOCK_EXTENSION
+#include "../plan9/lib.h"
 #include "../plan9/sys9.h"
+#define _LOCK_EXTENSION
 #include <lock.h>
 
-int	tas(int*);
-
 void
-lock(Lock *lk)
+lock(Lock *l)
 {
-	while(tas(&lk->val))
-		_SLEEP(0);
+	if(ainc(&l->key) == 1)
+		return;	/* changed from 0 -> 1: we hold lock */
+	/* otherwise wait in kernel */
+	while(_SEMACQUIRE(&l->sem, 1) < 0){
+		/* interrupted; try again */
+	}
 }
 
-int
-canlock(Lock *lk)
+void
+unlock(Lock *l)
 {
-	if(tas(&lk->val))
-		return 0;
-	return 1;
+	if(adec(&l->key) == 0)
+		return;	/* changed from 1 -> 0: no contention */
+	_SEMRELEASE(&l->sem, 1);
 }
 
-void
-unlock(Lock *lk)
+int
+canlock(Lock *l)
 {
-	lk->val = 0;
+	if(ainc(&l->key) == 1)
+		return 1;	/* changed from 0 -> 1: success */
+	/* Undo increment (but don't miss wakeup) */
+	if(adec(&l->key) == 0)
+		return 0;	/* changed from 1 -> 0: no contention */
+	_SEMRELEASE(&l->sem, 1);
+	return 0;
 }