X-Git-Url: https://pd.if.org/git/?p=zos;a=blobdiff_plain;f=spinlock.s;fp=spinlock.s;h=37849b2233dfc8aa341566d9d7fa112e862b2e73;hp=0000000000000000000000000000000000000000;hb=5a6d8336c11140500330da69cd74490a07876fe1;hpb=5c0e560e481e2e97b793f7574e849a5882781df9

diff --git a/spinlock.s b/spinlock.s
new file mode 100644
index 0000000..37849b2
--- /dev/null
+++ b/spinlock.s
@@ -0,0 +1,30 @@
+global spinlock_acquire:function
+global spinlock_release:function
+global spinlock_init:function
+
+; spinlock addr in rdi
+; low four bytes is ticket number
+; high four bytes is turn counter
+
+spinlock_init:
+	mov rax, 0
+	mov [rdi], rax
+	ret
+
+spinlock_acquire:
+	mov eax, 1
+	lock xadd [rdi], eax   ; eax = my ticket number
+
+	cmp [rdi+4], eax        ; is it my turn?
+	je .acquired             ; yes
+
+.retry:
+	pause
+	cmp [rdi+4], eax        ; is it my turn?
+	jne .retry                ; keep waiting
+.acquired:
+	ret
+
+spinlock_release:
+	lock inc dword [rdi+4]
+	ret