1 files changed, 26 insertions, 0 deletions
diff --git a/demo/lock.S b/demo/lock.S
new file mode 100644
index 0000000..3ec2765
--- /dev/null
+++ b/demo/lock.S
@@ -0,0 +1,26 @@
+.global spin_init
+spin_init:
+	mov     r1, #0
+	str     r1, [r0]
+	mov     pc, lr
+
+.global spin_lock
+spin_lock:
+	mrs     r2, cpsr
+	str     r2, [r1]
+	orr     r2, r2, #0xc0 @ Levanta I, F
+	msr     cpsr_c, r2
+	mov     r3, #1
+1:	ldrex   r2, [r0]
+	teq     r2, #0
+	strexeq r2, r3, [r0]
+	teqeq   r2, #0
+	bne     1b
+	mov     pc, lr
+
+.global spin_unlock
+spin_unlock:
+	mov     r2, #0
+	str     r2, [r0]
+	msr     cpsr_c, r1
+	mov     pc, lr