From 33c756b38e94cef68b3f842c1c2f8bad9d4447a2 Mon Sep 17 00:00:00 2001
From: UIS <uis9936@gmail.com>
Date: Thu, 10 Dec 2020 15:23:59 +0300
Subject: Fix multithreading

Reorder locks in Event.cpp
---
 src/Event.cpp | 43 +++++++++++++++++++++++--------------------
 1 file changed, 23 insertions(+), 20 deletions(-)

(limited to 'src/Event.cpp')

diff --git a/src/Event.cpp b/src/Event.cpp
index ea09af3..1ca933f 100644
--- a/src/Event.cpp
+++ b/src/Event.cpp
@@ -17,7 +17,7 @@ EventListener::~EventListener() {
 
 void EventListener::HandleEvent() {
 	OPTICK_EVENT();
-	if (!NotEmpty())
+	if (Empty())
 		return;
 
 	std::lock_guard<std::recursive_mutex> eventsLock (eventsMutex);
@@ -31,11 +31,14 @@ void EventListener::HandleEvent() {
 
 void EventListener::HandleAllEvents() {
 	OPTICK_EVENT();
-    if (!NotEmpty())
-        return;
 
+	//This mutexes will locked in PollEvents
 	std::lock_guard<std::recursive_mutex> eventsLock (eventsMutex);
-    std::lock_guard<std::recursive_mutex> handlersLock (handlersMutex);
+	std::lock_guard<std::recursive_mutex> handlersLock (handlersMutex);
+
+	if (Empty())
+		return;
+
 	while (!events.empty()) {
 		Event event = events.front();
 		events.pop();
@@ -45,11 +48,10 @@ void EventListener::HandleAllEvents() {
 	}
 }
 
-bool EventListener::NotEmpty() {
-    PollEvents();
+bool EventListener::Empty() {
 	std::lock_guard<std::recursive_mutex> eventsLock (eventsMutex);
-	bool ret = !events.empty();
-	return ret;
+	PollEvents();
+	return events.empty();
 }
 
 void EventListener::RegisterHandler(size_t eventId, const EventListener::HandlerType &data) {
@@ -59,16 +61,17 @@ void EventListener::RegisterHandler(size_t eventId, const EventListener::Handler
 
 void EventListener::PollEvents() {
 	OPTICK_EVENT();
-    std::lock_guard<std::recursive_mutex> rawLock (rawEventsMutex);
-    if (rawEvents.empty())
-        return;
-    
-    std::lock_guard<std::recursive_mutex> eventsLock (eventsMutex);
-    std::lock_guard<std::recursive_mutex> handlersLock (handlersMutex);
-    while (!rawEvents.empty()) {
-        Event event = rawEvents.front();
-        rawEvents.pop();
-        if (handlers[event.id])
-            events.push(event);
-    }
+	std::lock_guard<std::recursive_mutex> eventsLock (eventsMutex);
+	std::lock_guard<std::recursive_mutex> handlersLock (handlersMutex);//To prevent inverse lock order
+
+	std::lock_guard<std::recursive_mutex> rawLock (rawEventsMutex);
+	if (rawEvents.empty())
+		return;
+
+	while (!rawEvents.empty()) {
+		Event event = rawEvents.front();
+		rawEvents.pop();
+		if (handlers[event.id])
+			events.push(event);
+	}
 }
-- 
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