From e7f9c69a5fe88a3fea5a7dc3ce71e7ed337bdbd7 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Tue, 13 Mar 2018 18:56:31 +0100
Subject: [PATCH] (Hopefully! :-) ) fix some deadlocks during CEF shutdown.

---
 cef_capture.cpp    | 17 +++++++++++------
 cef_capture.h      |  4 +++-
 nageru_cef_app.cpp |  1 +
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/cef_capture.cpp b/cef_capture.cpp
index e46f0c0..ff978f2 100644
--- a/cef_capture.cpp
+++ b/cef_capture.cpp
@@ -41,7 +41,7 @@ CEFCapture::~CEFCapture()
 
 void CEFCapture::post_to_cef_ui_thread(std::function<void()> &&func)
 {
-	lock_guard<mutex> lock(browser_mutex);
+	lock_guard<recursive_mutex> lock(browser_mutex);
 	if (browser != nullptr) {
 		CefPostTask(TID_UI, new CEFTaskAdapter(std::move(func)));
 	} else {
@@ -113,7 +113,10 @@ void CEFCapture::OnPaint(const void *buffer, int width, int height)
 		// so we need to do this explicitly, or we could be stuck on an
 		// old frame forever if the image doesn't change.)
 		post_to_cef_ui_thread([this] {
-			browser->GetHost()->Invalidate(PET_VIEW);
+			lock_guard<recursive_mutex> lock(browser_mutex);
+			if (browser != nullptr) {  // Could happen if we are shutting down.
+				browser->GetHost()->Invalidate(PET_VIEW);
+			}
 		});
 		++timecode;
 	} else {
@@ -156,7 +159,7 @@ void CEFCapture::start_bm_capture()
 	cef_app->initialize_cef();
 
 	CefPostTask(TID_UI, new CEFTaskAdapter([this]{
-		lock_guard<mutex> lock(browser_mutex);
+		lock_guard<recursive_mutex> lock(browser_mutex);
 
 		CefBrowserSettings browser_settings;
 		browser_settings.web_security = cef_state_t::STATE_DISABLED;
@@ -175,9 +178,11 @@ void CEFCapture::start_bm_capture()
 
 void CEFCapture::stop_dequeue_thread()
 {
-	lock_guard<mutex> lock(browser_mutex);
-	cef_app->close_browser(browser);
-	browser = nullptr;  // Or unref_cef() will be sad.
+	{
+		lock_guard<recursive_mutex> lock(browser_mutex);
+		cef_app->close_browser(browser);
+		browser = nullptr;  // Or unref_cef() will be sad.
+	}
 	cef_app->unref_cef();
 }
 
diff --git a/cef_capture.h b/cef_capture.h
index 311076e..9e231c9 100644
--- a/cef_capture.h
+++ b/cef_capture.h
@@ -189,7 +189,9 @@ private:
 	std::string description, start_url;
 	std::atomic<int> max_fps{60};
 
-	std::mutex browser_mutex;
+	// Needs to be recursive because the lambda in OnPaint could cause
+	// OnPaint itself to be called.
+	std::recursive_mutex browser_mutex;
 	CefRefPtr<CefBrowser> browser;  // Under <browser_mutex>.
 
 	// Tasks waiting for <browser> to get ready. Under <browser_mutex>.
diff --git a/nageru_cef_app.cpp b/nageru_cef_app.cpp
index 2ddd816..2e64cee 100644
--- a/nageru_cef_app.cpp
+++ b/nageru_cef_app.cpp
@@ -38,6 +38,7 @@ void NageruCefApp::unref_cef()
 	unique_lock<mutex> lock(cef_mutex);
 	if (--cef_thread_refcount == 0) {
 		CefPostTask(TID_UI, new CEFTaskAdapter(&CefQuitMessageLoop));
+		lock.unlock();
 		cef_thread.join();
 	}
 }
-- 
2.39.2