Revert "Synchronise getter and setter of the cancelled property of the SDWebImageCombinedOperation in order to eliminate data race."

This reverts commit 5a18c84529.

SDWebImage/Core/SDWebImageManager.m

@@ -17,9 +17,7 @@
 static id<SDImageCache> _defaultImageCache;
 static id<SDImageLoader> _defaultImageLoader;
 
-@interface SDWebImageCombinedOperation () {
+@interface SDWebImageCombinedOperation ()
-    SD_LOCK_DECLARE(_cancelledLock); // a lock to keep the access to `cancelled` thread-safe
-}
 
 @property (assign, nonatomic, getter = isCancelled) BOOL cancelled;
 @property (strong, nonatomic, readwrite, nullable) id<SDWebImageOperation> loaderOperation;
@@ -805,29 +803,12 @@ static id<SDImageLoader> _defaultImageLoader;
 
 @implementation SDWebImageCombinedOperation
 
-- (instancetype)init {
-    if (self = [super init]) {
-        SD_LOCK_INIT(_cancelledLock);
-    }
-
-    return self;
-}
-
-- (BOOL)isCancelled {
-    BOOL isCancelled = NO;
-    SD_LOCK(_cancelledLock);
-    isCancelled = _cancelled;
-    SD_UNLOCK(_cancelledLock);
-    return isCancelled;
-}
-
 - (void)cancel {
-    SD_LOCK(_cancelledLock);
+    @synchronized(self) {
-    if (_cancelled) {
+        if (self.isCancelled) {
-        SD_UNLOCK(_cancelledLock);
             return;
         }
-    _cancelled = YES;
+        self.cancelled = YES;
         if (self.cacheOperation) {
             [self.cacheOperation cancel];
             self.cacheOperation = nil;
@@ -837,7 +818,7 @@ static id<SDImageLoader> _defaultImageLoader;
             self.loaderOperation = nil;
         }
         [self.manager safelyRemoveOperationFromRunning:self];
-    SD_UNLOCK(_cancelledLock);
+    }
 }
 
 @end