3 files changed, 18 insertions, 2 deletions
diff --git a/include/cpu.h b/include/cpu.h
index c200016..6dbaa74 100644
--- a/include/cpu.h
+++ b/include/cpu.h
@@ -91,5 +91,7 @@ static inline void* getirqstack(void)
 #define SYS_TIME        1
 #define SYS_SCHED       2
 #define SYS_FREE_STACK  3
+#define SYS_LOCK        4
+#define SYS_UNLOCK      5
 
 #endif
diff --git a/include/util/lock.h b/include/util/lock.h
new file mode 100644
index 0000000..78add88
--- /dev/null
+++ b/include/util/lock.h
@@ -0,0 +1,12 @@
+#ifndef UTIL_LOCK_H
+#define UTIL_LOCK_H
+
+#include <util/mutex.h>
+
+struct Lock {
+	unsigned long pid;
+} __attribute__((packed, aligned(4)));
+
+struct Lock* create_lock(void);
+
+#endif
diff --git a/include/util/mutex.h b/include/util/mutex.h
index 907fe5b..61237b8 100644
--- a/include/util/mutex.h
+++ b/include/util/mutex.h
@@ -8,10 +8,12 @@
 #define CORE3_PID 4
 #define FIRST_AVAIL_PID CORE3_PID+1
 
+// PID field is first so that it can be treated
+//  as a lock
 struct Mutex {
-	void* addr;
 	unsigned long pid;
-} __attribute__((packed, aligned(4)));;
+	void* addr;
+} __attribute__((packed, aligned(4)));
 
 struct Mutex* create_mutex(void* addr);