net80211: fix ieee80211_node_dectestref().

* sync with FreeBSD.
* implement atomic_cmpset_int() with atomic_test_and_set().

src/libs/compat/freebsd11_network/compat/machine/atomic.h

@@ -24,6 +24,9 @@
 #define atomic_readandclear_int(ptr) \
 	atomic_set((int32 *)(ptr), 0)
 
+#define atomic_cmpset_int(ptr, old, new) \
+	(atomic_test_and_set((int32 *)(ptr), new, old) == old)
+
 
 #define mb()    memory_full_barrier()
 #define wmb()   memory_write_barrier_inline()

src/libs/compat/freebsd_network/compat/machine/atomic.h

@@ -24,4 +24,8 @@
 #define atomic_readandclear_int(ptr) \
 	atomic_set((int32 *)(ptr), 0)
 
+#define atomic_cmpset_int(ptr, old, new) \
+	(atomic_test_and_set((int32 *)(ptr), new, old) == old)
+
+
 #endif	/* _FBSD_COMPAT_MACHINE_ATOMIC_H_ */

src/libs/compat/freebsd_wlan/net80211/ieee80211_haiku.cpp

@@ -454,7 +454,7 @@ ieee80211_getmgtframe(uint8_t** frm, int headroom, int pktlen)
 
 /*
  * Decrements the reference-counter and
- * tests whether it became zero.
+ * tests whether it became zero. If so, sets it to one.
  *
  * @return 1 reference-counter became zero
  * @return 0 reference-counter didn't became zero
@@ -462,8 +462,8 @@ ieee80211_getmgtframe(uint8_t** frm, int headroom, int pktlen)
 int
 ieee80211_node_dectestref(struct ieee80211_node* ni)
 {
-	// atomic_add returns old value
+	atomic_subtract_int(&ni->ni_refcnt, 1);
-	return atomic_add((int32*)&ni->ni_refcnt, -1) == 1;
+	return atomic_cmpset_int(&ni->ni_refcnt, 0, 1);
 }