From 759b7322c972e72cc3571b9adeae4b6fb62200cd Mon Sep 17 00:00:00 2001
From: zhongwuzw <zhongwuzw@qq.com>
Date: Fri, 31 Aug 2018 21:53:53 +0800
Subject: [PATCH] Remove lock tradeoff when get fetchFrame

---
 SDWebImage/SDAnimatedImageView.m | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/SDWebImage/SDAnimatedImageView.m b/SDWebImage/SDAnimatedImageView.m
index 0e6c52fd..9c7d4595 100644
--- a/SDWebImage/SDAnimatedImageView.m
+++ b/SDWebImage/SDAnimatedImageView.m
@@ -689,8 +689,10 @@ static NSUInteger SDDeviceFreeMemory() {
     
     // Update the current frame
     UIImage *currentFrame;
+    UIImage *fetchFrame;
     LOCKBLOCK({
         currentFrame = self.frameBuffer[@(currentFrameIndex)];
+        fetchFrame = currentFrame ? self.frameBuffer[@(nextFrameIndex)] : nil;
     });
     BOOL bufferFull = NO;
     if (currentFrame) {
@@ -744,11 +746,6 @@ static NSUInteger SDDeviceFreeMemory() {
         fetchFrameIndex = nextFrameIndex;
     }
     
-    UIImage *fetchFrame;
-    LOCKBLOCK({
-        fetchFrame = self.frameBuffer[@(fetchFrameIndex)];
-    });
-    
     if (!fetchFrame && !bufferFull && self.fetchQueue.operationCount == 0) {
         // Prefetch next frame in background queue
         UIImage<SDAnimatedImage> *animatedImage = self.animatedImage;