From e1c61cd2071df028d68b7ff71bde96104ac449b9 Mon Sep 17 00:00:00 2001
From: tux3 <barrdetwix@gmail.com>
Date: Sat, 24 Oct 2015 04:38:00 +0200
Subject: [PATCH] CoreVideoSource: Replace insane spinlock by QMutex

What was I thinking.
---
 src/video/corevideosource.cpp | 48 ++++++++++-------------------------
 src/video/corevideosource.h   |  3 ++-
 2 files changed, 15 insertions(+), 36 deletions(-)

diff --git a/src/video/corevideosource.cpp b/src/video/corevideosource.cpp
index 00576dff7..0a71b9b14 100644
--- a/src/video/corevideosource.cpp
+++ b/src/video/corevideosource.cpp
@@ -26,7 +26,7 @@ extern "C" {
 
 CoreVideoSource::CoreVideoSource()
     : subscribers{0}, deleteOnClose{false},
-      biglock{false}, stopped{false}
+    stopped{false}
 {
 }
 
@@ -35,12 +35,7 @@ void CoreVideoSource::pushFrame(const vpx_image_t* vpxframe)
     if (stopped)
         return;
 
-    // Fast lock
-    {
-        bool expected = false;
-        while (!biglock.compare_exchange_weak(expected, true))
-            expected = false;
-    }
+    QMutexLocker locker(&biglock);
 
     std::shared_ptr<VideoFrame> vframe;
     AVFrame* avframe;
@@ -49,11 +44,11 @@ void CoreVideoSource::pushFrame(const vpx_image_t* vpxframe)
     int dstStride, srcStride, minStride;
 
     if (subscribers <= 0)
-        goto end;
+        return;
 
     avframe = av_frame_alloc();
     if (!avframe)
-        goto end;
+        return;
     avframe->width = width;
     avframe->height = height;
     avframe->format = AV_PIX_FMT_YUV420P;
@@ -62,7 +57,7 @@ void CoreVideoSource::pushFrame(const vpx_image_t* vpxframe)
     if (!buf)
     {
         av_frame_free(&avframe);
-        goto end;
+        return;
     }
     avframe->opaque = buf;
 
@@ -80,63 +75,46 @@ void CoreVideoSource::pushFrame(const vpx_image_t* vpxframe)
 
     vframe = std::make_shared<VideoFrame>(avframe);
     emit frameAvailable(vframe);
-
-end:
-    biglock = false;
 }
 
 bool CoreVideoSource::subscribe()
 {
-    // Fast lock
-    {
-        bool expected = false;
-        while (!biglock.compare_exchange_weak(expected, true))
-            expected = false;
-    }
+    QMutexLocker locker(&biglock);
     ++subscribers;
-    biglock = false;
     return true;
 }
 
 void CoreVideoSource::unsubscribe()
 {
-    // Fast lock
-    {
-        bool expected = false;
-        while (!biglock.compare_exchange_weak(expected, true))
-            expected = false;
-    }
+    biglock.lock();
     if (--subscribers == 0)
     {
         if (deleteOnClose)
         {
-            biglock = false;
+            biglock.unlock();
+            // DANGEROUS: No member access after this point, that's why we manually unlock
             delete this;
             return;
         }
     }
-    biglock = false;
+    biglock.unlock();
 }
 
 void CoreVideoSource::setDeleteOnClose(bool newstate)
 {
-    // Fast lock
-    {
-        bool expected = false;
-        while (!biglock.compare_exchange_weak(expected, true))
-            expected = false;
-    }
+    QMutexLocker locker(&biglock);
     deleteOnClose = newstate;
-    biglock = false;
 }
 
 void CoreVideoSource::stopSource()
 {
+    QMutexLocker locker(&biglock);
     stopped = true;
     emit sourceStopped();
 }
 
 void CoreVideoSource::restartSource()
 {
+    QMutexLocker locker(&biglock);
     stopped = false;
 }
diff --git a/src/video/corevideosource.h b/src/video/corevideosource.h
index 888cc063a..b09b2ecc6 100644
--- a/src/video/corevideosource.h
+++ b/src/video/corevideosource.h
@@ -24,6 +24,7 @@
 #include <vpx/vpx_image.h>
 #include <atomic>
 #include "videosource.h"
+#include <QMutex>
 
 /// A VideoSource that emits frames received by Core
 class CoreVideoSource : public VideoSource
@@ -52,7 +53,7 @@ private:
 private:
     std::atomic_int subscribers; ///< Number of suscribers
     std::atomic_bool deleteOnClose; ///< If true, self-delete after the last suscriber is gone
-    std::atomic_bool biglock; ///< Fast lock
+    QMutex biglock;
     std::atomic_bool stopped;
 
 friend class CoreAV;