5 files changed, 47 insertions, 5 deletions
diff --git a/src/common/Makefile b/src/common/Makefile
index ef0f6b1..8698100 100644
--- a/src/common/Makefile
+++ b/src/common/Makefile
@@ -1,5 +1,5 @@
 Out = _common.o
-Obj = string.o
+Obj = string.o sched.o
 ExtObj = 
 
 include $(SrcPath)/common.make
diff --git a/src/common/include/sched.h b/src/common/include/sched.h
new file mode 100644
index 0000000..0f8f8f4
--- /dev/null
+++ b/src/common/include/sched.h
@@ -0,0 +1,15 @@
+#ifndef DEF_MUTEX_H
+#define DEF_MUTEX_H
+
+#include <types.h>
+
+#define MUTEX_LOCKED 1
+#define MUTEX_UNLOCKED 0
+
+//A mutex is just an uint32_t
+
+int mutex_lock(uint32_t* mutex);	//wait for mutex to be free
+int mutex_lockE(uint32_t* mutex);	//lock mutex only if free, returns !0 if locked, 0 if was busy
+void mutex_unlock(uint32_t* mutex);
+
+#endif
diff --git a/src/common/include/stdlib.h b/src/common/include/stdlib_common.h
index 2c5e6dd..80c188f 100644
--- a/src/common/include/stdlib.h
+++ b/src/common/include/stdlib_common.h
@@ -7,7 +7,7 @@
 #define MAX(a, b) ((a) > (b) ? (a) : (b))
 
 void *memcpy(void *dest, const void *src, int count);
-uint8_t *memset(uint8_t *dest, uint8_t val, int count);
+void *memset(void *dest, int val, int count);
 uint16_t *memsetw(uint16_t *dest, uint16_t val, int count);
 
 #endif
diff --git a/src/common/sched.c b/src/common/sched.c
new file mode 100644
index 0000000..29ea8a8
--- /dev/null
+++ b/src/common/sched.c
@@ -0,0 +1,26 @@
+#include <sched.h>
+
+/*	Internal use only. This function is atomic, meaning it cannot be interrupted by a system task switch. */
+static uint32_t atomic_exchange(uint32_t* ptr, uint32_t newval) {
+	uint32_t r;
+	asm volatile("xchg (%%ecx), %%eax" : "=a"(r) : "c"(ptr), "a"(newval));
+	return r;
+}
+
+int mutex_lock(uint32_t* mutex) {
+	while (atomic_exchange(mutex, MUTEX_LOCKED) == MUTEX_LOCKED) {
+		schedule();
+	}
+	return 0;
+}
+
+int mutex_lockE(uint32_t* mutex) {
+	if (atomic_exchange(mutex, MUTEX_LOCKED) == MUTEX_LOCKED) {
+		return 0;
+	}
+	return 1;
+}
+
+void mutex_unlock(uint32_t* mutex) {
+	*mutex = MUTEX_UNLOCKED;
+}
diff --git a/src/common/string.c b/src/common/string.c
index b2ec309..120fd5d 100644
--- a/src/common/string.c
+++ b/src/common/string.c
@@ -1,5 +1,5 @@
 #include <string.h>
-#include <stdlib.h>
+#include <stdlib_common.h>
 
 int strlen(const char *str) {
 	int i = 0;
@@ -63,10 +63,11 @@ void *memcpy(void *vd, const void *vs, int count) {
 	return vd;
 }
 
-uint8_t *memset(uint8_t *dest, uint8_t val, int count) {
+void *memset(void *dest, int val, int count) {
+	uint8_t *dest_c = (uint8_t*)dest;
 	int i;
 	for (i = 0; i < count; i++) {
-		dest[i] = val;
+		dest_c[i] = val;
 	}
 	return dest;
 }