libc: initial arm64 support

1 files changed, 41 insertions, 0 deletions

diff --git a/sys/src/libc/arm64/lock.c b/sys/src/libc/arm64/lock.c
new file mode 100644
index 000000000..307c4b7d6
--- /dev/null
+++ b/sys/src/libc/arm64/lock.c
@@ -0,0 +1,41 @@
+#include <u.h>
+#include <libc.h>
+
+extern uintptr _barrier(uintptr);
+
+void
+lock(Lock *lk)
+{
+	int i;
+
+	/* once fast */
+	if(!_tas(&lk->val))
+		return;
+	/* a thousand times pretty fast */
+	for(i=0; i<1000; i++){
+		if(!_tas(&lk->val))
+			return;
+		sleep(0);
+	}
+	/* now nice and slow */
+	for(i=0; i<1000; i++){
+		if(!_tas(&lk->val))
+			return;
+		sleep(100);
+	}
+	/* take your time */
+	while(_tas(&lk->val))
+		sleep(1000);
+}
+
+int
+canlock(Lock *lk)
+{
+	return _tas(&lk->val) == 0;
+}
+
+void
+unlock(Lock *lk)
+{
+	lk->val = _barrier(0);
+}