From e9d80f88e77fbb2c9738e6bda2ad82bdd003a434 Mon Sep 17 00:00:00 2001
From: Aleksey Kliger <alklig@microsoft.com>
Date: Tue, 12 Jan 2021 13:01:58 -0500
Subject: [PATCH 1/4] [mono] Set thread suspend default in mono.proj; default
 to hybrid

Instead of detecting in cmake, make a decision in mono.proj
---
 src/mono/CMakeLists.txt |  7 +++----
 src/mono/mono.proj      | 11 ++++++++++-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/mono/CMakeLists.txt b/src/mono/CMakeLists.txt
index 0df377c2cc2708..79c8a69aab5142 100644
--- a/src/mono/CMakeLists.txt
+++ b/src/mono/CMakeLists.txt
@@ -204,7 +204,6 @@ elseif(CMAKE_SYSTEM_NAME STREQUAL "Android")
   set(ANDROID_UNIFIED_HEADERS 1)
   set(ENABLE_MONODROID 1)
   set(DISABLE_EXECUTABLES 1)
-  set(GC_SUSPEND "hybrid")
   # Force some defines
   set(HAVE_SCHED_GETAFFINITY 0)
   set(HAVE_SCHED_SETAFFINITY 0)
@@ -255,9 +254,6 @@ if(TARGET_SYSTEM_NAME STREQUAL "Darwin")
   set(TARGET_MACH 1)
   set(TARGET_OSX 1)
   set(TARGET_DARWIN 1)
-  if (GC_SUSPEND STREQUAL "default")
-    set(GC_SUSPEND "hybrid")
-  endif()
 elseif(TARGET_SYSTEM_NAME STREQUAL "iOS" OR TARGET_SYSTEM_NAME STREQUAL "tvOS")
   set(TARGET_MACH 1)
   set(TARGET_IOS 1)
@@ -543,6 +539,9 @@ if (GC_SUSPEND STREQUAL "coop")
   set(ENABLE_COOP_SUSPEND 1)
 elseif(GC_SUSPEND STREQUAL "hybrid")
   set(ENABLE_HYBRID_SUSPEND 1)
+elseif(GC_SUSPEND STREQUAL "preemptive")
+else()
+  message(FATAL_ERROR "GC_SUSPEND (set to '${GC_SUSPEND}') must be one of coop, hybrid or preemptive")
 endif()
 
 ######################################
diff --git a/src/mono/mono.proj b/src/mono/mono.proj
index c460c4515dafc2..1e53b595f0ad2c 100644
--- a/src/mono/mono.proj
+++ b/src/mono/mono.proj
@@ -9,6 +9,7 @@
       - MonoAOTLLVMDir - [optional] the directory where LLVM is located, for an AOT-only Mono
       - MonoVerboseBuild - enable verbose build
       - MonoMetadataUpdate - enable experimental method body replacement code
+      - MonoThreadSuspend - coop,hybrid,preemptive - default thread suspend mode
   -->
 
   <PropertyGroup>
@@ -45,6 +46,10 @@
     <MonoCCompiler Condition="$(MonoCCompiler.StartsWith('-'))">$(MonoCCompiler.TrimStart('-'))</MonoCCompiler>
     <MonoCxxCompiler Condition="'$(MonoCCompiler)' == 'clang'">clang++</MonoCxxCompiler>
     <MonoCxxCompiler Condition="'$(MonoCCompiler)' == 'gcc'">g++</MonoCxxCompiler>
+    <!-- default thread suspend for specific platforms -->
+    <MonoThreadSuspend Condition="'$(TargetswatchOS)' == 'true'">coop</MonoThreadSuspend>
+    <!-- default thread suspend for all platforms -->
+    <MonoThreadSuspend Condition="'$(MonoThreadSuspend)' == ''">hybrid</MonoThreadSuspend>
   </PropertyGroup>
 
   <ItemGroup Condition="'$(TargetsBrowser)' == 'true'">
@@ -124,6 +129,7 @@
       <_MonoCMakeArgs Include="-DCMAKE_INSTALL_LIBDIR=lib"/>
       <_MonoCMakeArgs Include="-DCMAKE_BUILD_TYPE=$(Configuration)"/>
       <_MonoCMakeArgs Condition="'$(MonoEnableLLVM)' == 'true'" Include="-DLLVM_PREFIX=$(MonoLLVMDir)" />
+      <_MonoCMakeArgs Include="-DGC_SUSPEND=$(MonoThreadSuspend)" />
     </ItemGroup>
 
     <!-- We build LLVM bits for x64 Linux without C++11 ABI (CentOS 7 has libstdc++ < 5.1) -->
@@ -414,7 +420,10 @@
       <!-- FIXME: Add sanity check that the interpreter is enabled -->
       <MonoAOTCMakeArgs Condition="'$(MonoMetadataUpdate)' == 'true'" Include="-DENABLE_METADATA_UPDATE=1" />
 
-      <!-- Select generator platform for VS generator -->
+      <!-- thread suspend -->
+      <MonoAOTCMakeArgs Include="-DGC_SUSPEND=$(MonoThreadSuspend)" />
+ 
+     <!-- Select generator platform for VS generator -->
       <MonoAOTCMakeArgs Condition="'$(OS)' == 'Windows_NT' and '$(_MonoUseNinja)' != 'true' and '$(Platform)' == 'x64'" Include="-A x64" />
       <MonoAOTCMakeArgs Condition="'$(OS)' == 'Windows_NT' and '$(_MonoUseNinja)' != 'true' and '$(Platform)' == 'x86'" Include="-A Win32" />
       <MonoAOTCMakeArgs Condition="'$(OS)' == 'Windows_NT' and '$(_MonoUseNinja)' != 'true' and '$(Platform)' == 'arm'" Include="-A ARM" />

From c0b635c5ce27ed8c582d07d834f44dd87d4d4a43 Mon Sep 17 00:00:00 2001
From: Aleksey Kliger <alklig@microsoft.com>
Date: Fri, 15 Jan 2021 13:02:57 -0500
Subject: [PATCH 2/4] [cmake] Pick a fallback suspend policy if GC_SUSPEND is
 default

---
 src/mono/CMakeLists.txt | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/mono/CMakeLists.txt b/src/mono/CMakeLists.txt
index 79c8a69aab5142..85ea53471d70ad 100644
--- a/src/mono/CMakeLists.txt
+++ b/src/mono/CMakeLists.txt
@@ -540,6 +540,15 @@ if (GC_SUSPEND STREQUAL "coop")
 elseif(GC_SUSPEND STREQUAL "hybrid")
   set(ENABLE_HYBRID_SUSPEND 1)
 elseif(GC_SUSPEND STREQUAL "preemptive")
+elseif(GC_SUSPEND STREQUAL "default")
+  # set some kind of fallback default
+  if(TARGET_SYSTEM_NAME STREQUAL "watchOS")
+    set(ENABLE_COOP_SUSPEND 1)
+  elseif(TARGET_SYSTEM_NAME STREQUAL "Windows")
+    # use preemptive
+  else()
+    set(ENABLE_HYBRID_SUSPEND 1)
+  endif()
 else()
   message(FATAL_ERROR "GC_SUSPEND (set to '${GC_SUSPEND}') must be one of coop, hybrid or preemptive")
 endif()

From fe00669b1fbfe3f386181bf0e175ca2f4c5ef7cd Mon Sep 17 00:00:00 2001
From: Aleksey Kliger <alklig@microsoft.com>
Date: Fri, 15 Jan 2021 14:31:24 -0500
Subject: [PATCH 3/4] cleanup mono.proj

---
 src/mono/mono.proj | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/mono/mono.proj b/src/mono/mono.proj
index 1e53b595f0ad2c..55ac82e6ab8e5c 100644
--- a/src/mono/mono.proj
+++ b/src/mono/mono.proj
@@ -46,9 +46,12 @@
     <MonoCCompiler Condition="$(MonoCCompiler.StartsWith('-'))">$(MonoCCompiler.TrimStart('-'))</MonoCCompiler>
     <MonoCxxCompiler Condition="'$(MonoCCompiler)' == 'clang'">clang++</MonoCxxCompiler>
     <MonoCxxCompiler Condition="'$(MonoCCompiler)' == 'gcc'">g++</MonoCxxCompiler>
-    <!-- default thread suspend for specific platforms -->
-    <MonoThreadSuspend Condition="'$(TargetswatchOS)' == 'true'">coop</MonoThreadSuspend>
-    <!-- default thread suspend for all platforms -->
+  </PropertyGroup>
+
+  <!-- default thread suspend for specific platforms -->
+  <PropertyGroup>
+    <MonoThreadSuspend Condition="'$(TargetswatchOS)' == 'true' and '$(MonoThreadSuspend)' == ''">coop</MonoThreadSuspend>
+    <!-- all other platforms -->
     <MonoThreadSuspend Condition="'$(MonoThreadSuspend)' == ''">hybrid</MonoThreadSuspend>
   </PropertyGroup>
 

From 48f8e55cc4a3ed2ee356f5ab45cbfac68514f95f Mon Sep 17 00:00:00 2001
From: Aleksey Kliger <alklig@microsoft.com>
Date: Fri, 15 Jan 2021 14:31:35 -0500
Subject: [PATCH 4/4] default to "preemptive" on wasm

It isn't really preemptive, it just turns off safepoint code in the AOT
compiler.  This is fine for single threaded.
---
 src/mono/CMakeLists.txt | 2 ++
 src/mono/mono.proj      | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/src/mono/CMakeLists.txt b/src/mono/CMakeLists.txt
index 85ea53471d70ad..e0e4a64f70f38a 100644
--- a/src/mono/CMakeLists.txt
+++ b/src/mono/CMakeLists.txt
@@ -546,6 +546,8 @@ elseif(GC_SUSPEND STREQUAL "default")
     set(ENABLE_COOP_SUSPEND 1)
   elseif(TARGET_SYSTEM_NAME STREQUAL "Windows")
     # use preemptive
+  elseif(TARGET_SYSTEM_NAME STREQUAL "Emscripten")
+    # use preemptive
   else()
     set(ENABLE_HYBRID_SUSPEND 1)
   endif()
diff --git a/src/mono/mono.proj b/src/mono/mono.proj
index 55ac82e6ab8e5c..d629d103b53c24 100644
--- a/src/mono/mono.proj
+++ b/src/mono/mono.proj
@@ -51,6 +51,8 @@
   <!-- default thread suspend for specific platforms -->
   <PropertyGroup>
     <MonoThreadSuspend Condition="'$(TargetswatchOS)' == 'true' and '$(MonoThreadSuspend)' == ''">coop</MonoThreadSuspend>
+    <!-- wasm isn't really preemptive, but we don't want safepoints -->
+    <MonoThreadSuspend Condition="'$(TargetsBrowser)' == 'true' and '$(MonoThreadSuspend)' == ''">preemptive</MonoThreadSuspend>
     <!-- all other platforms -->
     <MonoThreadSuspend Condition="'$(MonoThreadSuspend)' == ''">hybrid</MonoThreadSuspend>
   </PropertyGroup>