Need the reads on the property to be atomic as well. Otherwise there as cases like 'startAnimating' getting called from two seperate threads. Each would read a value A. The first thread would then write the value A+1. Thread 2 also read A so it would also write A+1. As a result missing an increment

AFNetworking/AFNetworkActivityIndicatorManager.m

@@ -23,7 +23,7 @@
 #import "AFNetworkActivityIndicatorManager.h"
 
 @interface AFNetworkActivityIndicatorManager ()
-@property (readwrite, nonatomic, assign) NSInteger activityCount;
+@property (readwrite, assign) NSInteger activityCount;
 @end
 
 @implementation AFNetworkActivityIndicatorManager