From 1567c1c8d6c998e043f39c511e2acd562f7dbaa9 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Tue, 31 Oct 2023 14:15:35 +0100
Subject: [PATCH] Fix Mono AOT on iOS to not freeze during GC stop-the-world
 event on memory collection

---
 Source/Engine/Engine/NativeInterop.Unmanaged.cs | 3 ---
 Source/Engine/Scripting/Runtime/DotNet.cpp      | 7 +++++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/Source/Engine/Engine/NativeInterop.Unmanaged.cs b/Source/Engine/Engine/NativeInterop.Unmanaged.cs
index 5af1569b9..0391974b6 100644
--- a/Source/Engine/Engine/NativeInterop.Unmanaged.cs
+++ b/Source/Engine/Engine/NativeInterop.Unmanaged.cs
@@ -1181,10 +1181,7 @@ namespace FlaxEngine.Interop
         [UnmanagedCallersOnly]
         internal static void GCCollect(int generation, int mode, bool blocking, bool compacting)
         {
-            // TODO: fix stall on iOS with AOT
-#if !USE_AOT
             GC.Collect(generation, (GCCollectionMode)mode, blocking, compacting);
-#endif
         }
 
         [UnmanagedCallersOnly]
diff --git a/Source/Engine/Scripting/Runtime/DotNet.cpp b/Source/Engine/Scripting/Runtime/DotNet.cpp
index b3e5a0072..91b1d3dde 100644
--- a/Source/Engine/Scripting/Runtime/DotNet.cpp
+++ b/Source/Engine/Scripting/Runtime/DotNet.cpp
@@ -46,6 +46,7 @@
 #include <mono/metadata/metadata.h>
 #include <mono/metadata/threads.h>
 #include <mono/metadata/reflection.h>
+#include <mono/metadata/mono-gc.h>
 #include <mono/metadata/mono-private-unstable.h>
 typedef char char_t;
 #define DOTNET_HOST_MONO_DEBUG 0
@@ -522,7 +523,8 @@ void MCore::GC::FreeMemory(void* ptr, bool coTaskMem)
 
 void MCore::Thread::Attach()
 {
-#if DOTNET_HOST_MONO
+    // TODO: find a way to properly register native thread so Mono Stop The World (stw) won't freeze when native threads (eg. Job System) are running native code only
+#if DOTNET_HOST_MONO && !USE_MONO_AOT
     if (!IsInMainThread() && !mono_domain_get())
     {
         mono_thread_attach(MonoDomainHandle);
@@ -2056,7 +2058,7 @@ bool InitHostfxr()
     // Setup debugger
     {
         int32 debuggerLogLevel = 0;
-        if (CommandLine::Options.MonoLog.IsTrue())
+        if (CommandLine::Options.MonoLog.IsTrue() || DOTNET_HOST_MONO_DEBUG)
         {
             LOG(Info, "Using detailed Mono logging");
             mono_trace_set_level_string("debug");
@@ -2139,6 +2141,7 @@ bool InitHostfxr()
         LOG(Fatal, "Failed to initialize Mono.");
         return true;
     }
+    mono_gc_init_finalizer_thread();
 
     // Log info
     char* buildInfo = mono_get_runtime_build_info();