Merge pull request #9 from uber/fix_nscondition_loop

Fix CountDownLatch usage of NSCondition

Author: neakor

Concurrency.xcodeproj/project.pbxproj

@@ -34,14 +34,14 @@
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
-		413AD8C020AF73AB00AD7F36 /* PBXContainerItemProxy */ = {
+		412CDD2D20B88EAB00AF5890 /* PBXContainerItemProxy */ = {
 			isa = PBXContainerItemProxy;
 			containerPortal = OBJ_1 /* Project object */;
 			proxyType = 1;
 			remoteGlobalIDString = "Concurrency::Concurrency";
 			remoteInfo = Concurrency;
 		};
-		413AD8C120AF73AB00AD7F36 /* PBXContainerItemProxy */ = {
+		412CDD2E20B88EAB00AF5890 /* PBXContainerItemProxy */ = {
 			isa = PBXContainerItemProxy;
 			containerPortal = OBJ_1 /* Project object */;
 			proxyType = 1;
@@ -258,12 +258,12 @@
 		OBJ_42 /* PBXTargetDependency */ = {
 			isa = PBXTargetDependency;
 			target = "Concurrency::ConcurrencyTests" /* ConcurrencyTests */;
-			targetProxy = 413AD8C120AF73AB00AD7F36 /* PBXContainerItemProxy */;
+			targetProxy = 412CDD2E20B88EAB00AF5890 /* PBXContainerItemProxy */;
 		};
 		OBJ_54 /* PBXTargetDependency */ = {
 			isa = PBXTargetDependency;
 			target = "Concurrency::Concurrency" /* Concurrency */;
-			targetProxy = 413AD8C020AF73AB00AD7F36 /* PBXContainerItemProxy */;
+			targetProxy = 412CDD2D20B88EAB00AF5890 /* PBXContainerItemProxy */;
 		};
 /* End PBXTargetDependency section */
 

Sources/Concurrency/CountDownLatch.swift

@@ -81,12 +81,18 @@ public class CountDownLatch {
         }
 
         condition.lock()
+        defer {
+            condition.unlock()
+        }
         // Check count again after acquiring the lock, before entering waiting. This ensures the caller
         // does not enter waiting after the last counting down occurs.
-        if conditionCount.value > 0 {
-            return condition.wait(until: deadline)
+        // NSCondition must be run in a loop, since it can wake up randomly without any siganling.
+        while conditionCount.value > 0 {
+            let result = condition.wait(until: deadline)
+            if !result || Date() > deadline {
+                return false
+            }
         }
-        condition.unlock()
         return true
     }