feat: seq_cst implementation

atomic.go

@@ -0,0 +1,13 @@
+package gouring
+
+import _ "unsafe"
+
+var io_uring_smp_mb = io_uring_smp_mb_fallback
+
+func io_uring_smp_mb_fallback()
+func io_uring_smp_mb_mfence()
+
+func init() {
+	// temporary
+	io_uring_smp_mb = io_uring_smp_mb_mfence
+}

atomic_amd64.s

@@ -0,0 +1,12 @@
+#include "go_asm.h"
+#include "funcdata.h"
+#include "textflag.h"
+
+TEXT ·io_uring_smp_mb_fallback(SB), NOSPLIT, $0
+    LOCK
+    ORQ $0, 0(SP)
+    RET
+
+TEXT ·io_uring_smp_mb_mfence(SB), NOSPLIT, $0
+    MFENCE
+    RET

queue.go

@@ -19,7 +19,8 @@ func (ring *IoUring) sq_ring_needs_enter(flags *uint32) bool {
 		return true
 	}
 
-	// FIXME: io_uring_smp_mb
+	// FIXME: Extra call - no inline asm.
+	io_uring_smp_mb()
 
 	if atomic.LoadUint32(ring.Sq._Flags())&IORING_SQ_NEED_WAKEUP != 0 {
 		*flags |= IORING_ENTER_SQ_WAKEUP