Added mutex_control syscall for userspace mutexes.

- Compiles and Codezero runs as normal without touching mutex implementation
- Mutex implementation needs testing.

The mutex control syscall allows userspace programs to declare any virtual
address as a mutex lock and ask for help from the kernel syscall
for resolving locking contentions.

tasks/libl4/include/l4lib/arch-arm/syscalls.h

@@ -78,6 +78,10 @@ typedef int (*__l4_time_t)(void *timeval, int set);
 extern __l4_time_t __l4_time;
 int l4_time(void *timeval, int set);
 
+typedef int (*__l4_mutex_control_t)(void *mutex_word, int op);
+extern __l4_mutex_control_t __l4_mutex_control;
+int l4_mutex_control(void *mutex_word, int op);
+
 
 /* To be supplied by server tasks. */
 void *virt_to_phys(void *);

tasks/libl4/include/l4lib/mutex.h

@@ -0,0 +1,38 @@
+
+/*
+ * User space locking
+ *
+ * Copyright (C) 2009 Bahadir Bilgehan Balban
+ */
+
+#ifndef __L4_MUTEX_H__
+#define __L4_MUTEX_H__
+
+
+#if !defined(__ASSEMBLY__)
+
+#include <l4/api/mutex.h>
+
+struct l4_mutex {
+	unsigned int lock;
+} __attribute__((aligned(sizeof(int))));
+
+
+void l4_mutex_init(struct l4_mutex *m);
+int l4_mutex_lock(struct l4_mutex *m);
+int l4_mutex_unlock(struct l4_mutex *m);
+
+#endif
+
+/* Mutex return value - don't mix up with mutes state */
+#define L4_MUTEX_CONTENDED	-1
+#define L4_MUTEX_SUCCESS	0
+
+/* Mutex states - Any valid tid value is a locked state */
+#define L4_MUTEX_UNLOCKED		-1
+#define L4_MUTEX(m)	\
+	struct l4_mutex m = { L4_MUTEX_UNLOCKED }
+
+
+
+#endif /* __L4_MUTEX_H__ */