From f0659b4f3c61fd4652e12bf1b3b0ad7fa1112d9d Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Tue, 18 Jan 2022 18:19:28 -0600
Subject: [PATCH] Fix random crash on stream start with renderers that require
 test frames

---
 app/streaming/session.cpp      |  7 +++++++
 app/streaming/video/ffmpeg.cpp | 14 ++++++++------
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/app/streaming/session.cpp b/app/streaming/session.cpp
index f1a33119..9d202cbb 100644
--- a/app/streaming/session.cpp
+++ b/app/streaming/session.cpp
@@ -819,6 +819,11 @@ private:
             emit m_Session->sessionFinished(m_Session->m_PortTestResults);
         }
 
+        // The video decoder must already be destroyed, since it could
+        // try to interact with APIs that can only be called between
+        // LiStartConnection() and LiStopConnection().
+        SDL_assert(m_Session->m_VideoDecoder == nullptr);
+
         // Finish cleanup of the connection state
         LiStopConnection();
 
@@ -1717,6 +1722,8 @@ DispatchDeferredCleanup:
     SDL_AtomicUnlock(&m_InputHandlerLock);
 
     // Destroy the decoder, since this must be done on the main thread
+    // NB: This must happen before LiStopConnection() for pull-based
+    // decoders.
     SDL_AtomicLock(&m_DecoderLock);
     delete m_VideoDecoder;
     m_VideoDecoder = nullptr;
diff --git a/app/streaming/video/ffmpeg.cpp b/app/streaming/video/ffmpeg.cpp
index 465bbe86..27d8529b 100644
--- a/app/streaming/video/ffmpeg.cpp
+++ b/app/streaming/video/ffmpeg.cpp
@@ -424,13 +424,15 @@ bool FFmpegVideoDecoder::completeInitialization(const AVCodec* decoder, PDECODER
 
         // Tell overlay manager to use this frontend renderer
         Session::get()->getOverlayManager().setOverlayRenderer(m_FrontendRenderer);
-    }
 
-    m_DecoderThread = SDL_CreateThread(FFmpegVideoDecoder::decoderThreadProcThunk, "FFDecoder", (void*)this);
-    if (m_DecoderThread == nullptr) {
-        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
-                     "Failed to create decoder thread: %s", SDL_GetError());
-        return false;
+        // Only create the decoder thread when instantiating the decoder for real. It will use APIs from
+        // moonlight-common-c that can only be legally called with an established connection.
+        m_DecoderThread = SDL_CreateThread(FFmpegVideoDecoder::decoderThreadProcThunk, "FFDecoder", (void*)this);
+        if (m_DecoderThread == nullptr) {
+            SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                         "Failed to create decoder thread: %s", SDL_GetError());
+            return false;
+        }
     }
 
     return true;