Feature and ifdef FEATURE_MULTITHREADING

[pavelsavara]

No description provided.

[Copilot]

Pull request overview

This PR refactors the threading feature detection mechanism in the .NET runtime by consolidating multiple threading-related feature flags into a single, consistently-named flag: FEATURE_IS_MULTITHREADING_SUPPORTED. This replaces the previous FEATURE_WASM_MANAGED_THREADS and FEATURE_SINGLE_THREADED flags with clearer, more consistent naming.

Changes:

• Renamed MSBuild property FeatureWasmManagedThreads to FeatureIsMultithreadingSupported across all project files
• Renamed C# preprocessor define FEATURE_WASM_MANAGED_THREADS to FEATURE_IS_MULTITHREADING_SUPPORTED
• Removed FEATURE_SINGLE_THREADED and FeatureSingleThread in favor of checking !FEATURE_IS_MULTITHREADING_SUPPORTED
• Updated documentation in threads.md to reflect the new naming
• Updated C/C++ PAL layer code to use FEATURE_IS_MULTITHREADING_SUPPORTED (with appropriate #ifdef/#ifndef usage)

Reviewed changes

Copilot reviewed 68 out of 68 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/mono/wasm/threads.md	Updated documentation to reference new feature flag name
src/mono/System.Private.CoreLib/System.Private.CoreLib.csproj	Consolidated feature properties, removed separate single-thread property
src/mono/System.Private.CoreLib/src/System/Threading/Monitor.Mono.cs	Updated preprocessor directive
src/libraries/System.Threading/src/System.Threading.csproj	Updated feature property definition and condition logic
src/libraries/System.Threading/src/System/Threading/*.cs	Updated preprocessor directives in source files
src/libraries/System.Threading/ref/System.Threading.cs	Updated preprocessor directives in reference assembly
src/libraries/System.Threading.Thread*/ref/*.csproj	Updated feature property references in WebAssembly threading projects
src/libraries/System.Threading.ThreadPool*/ref/*.csproj	Updated feature property references
src/libraries/System.Threading.Tasks.Parallel/src/*.csproj	Removed separate single-thread flag, using unified flag
src/libraries/System.Runtime.InteropServices.JavaScript/src/*.cs	Updated all preprocessor directives across JavaScript interop
src/libraries/System.Runtime.InteropServices.JavaScript/src/*.csproj	Updated feature property and conditions
src/libraries/System.Runtime.InteropServices.JavaScript/tests/*.cs	Updated test code preprocessor directives
src/libraries/System.Private.CoreLib/src/System/Threading/*.cs	Updated threading implementation files
src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeFeature.cs	Refactored conditional compilation blocks
src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems	Updated file inclusion conditions
src/libraries/System.Private.CoreLib/ref/*.cs	Updated reference assembly definitions
src/libraries/System.Net.WebSockets.Client/src/*.cs	Updated WebSocket implementation
src/libraries/System.Net.Http/src/System.Net.Http.csproj	Removed unused feature property
src/libraries/System.Linq.Parallel/src/*.cs	Updated PLINQ implementation files
src/libraries/System.Linq.Parallel/src/System.Linq.Parallel.csproj	Consolidated feature flags
src/libraries/Common/src/Interop/Browser/Interop.Runtime.Mono.cs	Updated interop declarations
src/coreclr/pal/src/thread/*.cpp	Updated PAL thread implementation with inverted conditional logic
src/coreclr/pal/src/synchmgr/*.cpp	Updated synchronization manager implementation
src/coreclr/pal/src/CMakeLists.txt	Updated CMake definitions
src/coreclr/clrdefinitions.cmake	Updated CMake feature definitions
src/coreclr/clr.featuredefines.props	Consolidated feature properties
eng/native.wasm.targets	Updated native build conditions and CMake arguments

[jkotas]

We do not have any FEATURE_IS_.*. FEATURE_ABC means ABC is supported.

I think it should be FeatureMultithreadingSupport / FEATURE_MULTITHREADING_SUPPORT, or just FeatureMultithreading / FEATURE_MULTITHREADING, to match the naming pattern we use for the feature properties and defines.

[Copilot]

Pull request overview

Copilot reviewed 68 out of 68 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 74 out of 74 changed files in this pull request and generated 5 comments.

[Copilot]

Pull request overview

Copilot reviewed 74 out of 74 changed files in this pull request and generated 5 comments.

[Copilot]

Pull request overview

Copilot reviewed 25 out of 25 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 25 out of 25 changed files in this pull request and generated 2 comments.

[Copilot]

System.Net.WebSockets.Client no longer defines FEATURE_WASM_MANAGED_THREADS, but BrowserWebSocket.Dispose() still uses #if FEATURE_WASM_MANAGED_THREADS to decide whether to marshal cleanup onto the JS synchronization context. With the define removed, threaded WASM builds will always take the non-threaded path, which can break cleanup when Dispose runs on the finalizer thread. Re-introduce the define for the browser target when WasmEnableThreads=true, or update the source to key off the new multithreading define/property consistently.

Suggested change

	<PropertyGroup Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(WasmEnableThreads)' == 'true'">
	<DefineConstants>$(DefineConstants);FEATURE_WASM_MANAGED_THREADS</DefineConstants>
	</PropertyGroup>

[Copilot]

Pull request overview

Copilot reviewed 25 out of 25 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 25 out of 25 changed files in this pull request and generated no new comments.

[jkotas]

Suggested change

	<Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\EventPipeEventDispatcher.Threads.cs" Condition="'$(FeaturePerfTracing)' == 'true' and (('$(TargetsWasi)' != 'true' and '$(TargetsBrowser)' != 'true') or '$(FeatureMultithreading)' == 'true')" />
	<Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\EventPipeEventDispatcher.Wasm.cs" Condition="'$(FeaturePerfTracing)' == 'true' and (('$(TargetsWasi)' == 'true' or '$(TargetsBrowser)' == 'true') and '$(FeatureMultithreading)' != 'true')" />
	<Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\EventPipeEventDispatcher.Threads.cs" Condition="'$(FeaturePerfTracing)' == 'true' and '$(FeatureMultithreading)' == 'true'" />
	<Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\EventPipeEventDispatcher.Wasm.cs" Condition="'$(FeaturePerfTracing)' == 'true' and '$(FeatureMultithreading)' != 'true')" />

[jkotas]

Suggested change

	<ItemGroup Condition="('$(TargetsBrowser)' == 'true' or '$(TargetsWasi)' == 'true') and '$(FeatureMultithreading)' != 'true'">
	<ItemGroup Condition="'$(FeatureMultithreading)' != 'true'">

[jkotas]

Suggested change

	<Compile Include="$(MSBuildThisFileDirectory)System\Threading\PreAllocatedOverlapped.Portable.cs" Condition="('$(TargetsBrowser)' != 'true' and '$(TargetsWasi)' != 'true') or '$(FeatureMultithreading)' == 'true'" />
	<Compile Include="$(MSBuildThisFileDirectory)System\Threading\PreAllocatedOverlapped.Portable.cs" Condition="'$(FeatureMultithreading)' == 'true'" />

[jkotas]

Is there a reason why we cannot use PreAllocatedOverlapped.Portable.cs for single-threaded Wasm? It should be unreachable trimmable code on non-Windows, so it should not affect size of retail apps.