From a8f13ccad400eb8ff84a379042c0595951ca9658 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?K=C3=A1ri=20Tristan=20Helgason?= <kthelgason@webrtc.org>
Date: Thu, 5 Apr 2018 11:48:00 +0200
Subject: [PATCH] Improve thread-safety of MTL Renderer.
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Bug: b/77579859
Change-Id: I427d0f41593155dc5cbf98a09d7ec826497b803c
Reviewed-on: https://webrtc-review.googlesource.com/67040
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22795}
---
 .../Classes/Metal/RTCMTLNV12Renderer.mm       |  2 ++
 .../Framework/Classes/Metal/RTCMTLVideoView.m | 22 +++++++++----------
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/sdk/objc/Framework/Classes/Metal/RTCMTLNV12Renderer.mm b/sdk/objc/Framework/Classes/Metal/RTCMTLNV12Renderer.mm
index 079b5fb76c..6de9c347e6 100644
--- a/sdk/objc/Framework/Classes/Metal/RTCMTLNV12Renderer.mm
+++ b/sdk/objc/Framework/Classes/Metal/RTCMTLNV12Renderer.mm
@@ -18,6 +18,7 @@
 #import "WebRTC/RTCVideoFrameBuffer.h"
 
 #import "RTCMTLRenderer+Private.h"
+#include "rtc_base/checks.h"
 
 #define MTL_STRINGIFY(s) @ #s
 
@@ -85,6 +86,7 @@ static NSString *const shaderSource = MTL_STRINGIFY(
 }
 
 - (BOOL)setupTexturesForFrame:(nonnull RTCVideoFrame *)frame {
+  RTC_DCHECK([frame.buffer isKindOfClass:[RTCCVPixelBuffer class]]);
   [super setupTexturesForFrame:frame];
   CVPixelBufferRef pixelBuffer = ((RTCCVPixelBuffer *)frame.buffer).pixelBuffer;
 
diff --git a/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m b/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m
index 0e17777c4a..e343bb48b4 100644
--- a/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m
+++ b/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m
@@ -105,32 +105,32 @@
 
 - (void)drawInMTKView:(nonnull MTKView *)view {
   NSAssert(view == self.metalView, @"Receiving draw callbacks from foreign instance.");
-  if (!self.videoFrame) {
+  RTCVideoFrame *videoFrame = self.videoFrame;
+  if (!videoFrame) {
     return;
   }
 
-  id<RTCMTLRenderer> renderer = nil;
-  if ([self.videoFrame.buffer isKindOfClass:[RTCCVPixelBuffer class]]) {
-    if (!self.rendererNV12) {
+  if ([videoFrame.buffer isKindOfClass:[RTCCVPixelBuffer class]]) {
+    static dispatch_once_t nv12_token;
+    dispatch_once(&nv12_token, ^{
       self.rendererNV12 = [RTCMTLVideoView createNV12Renderer];
       if (![self.rendererNV12 addRenderingDestination:self.metalView]) {
         self.rendererNV12 = nil;
         RTCLogError(@"Failed to create NV12 renderer");
       }
-    }
-    renderer = self.rendererNV12;
+    });
+    [self.rendererNV12 drawFrame:videoFrame];
   } else {
-    if (!self.rendererI420) {
+    static dispatch_once_t i420_token;
+    dispatch_once(&i420_token, ^{
       self.rendererI420 = [RTCMTLVideoView createI420Renderer];
       if (![self.rendererI420 addRenderingDestination:self.metalView]) {
         self.rendererI420 = nil;
         RTCLogError(@"Failed to create I420 renderer");
       }
-    }
-    renderer = self.rendererI420;
+    });
+    [self.rendererI420 drawFrame:videoFrame];
   }
-
-  [renderer drawFrame:self.videoFrame];
 }
 
 - (void)mtkView:(MTKView *)view drawableSizeWillChange:(CGSize)size {