Skip to content

Avoid duplicate ValueTask checks in transparent awaits #133023

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
jakobbotsch wants to merge 1 commit into
base: main
Choose a base branch
from
+66 −82
Open

Avoid duplicate ValueTask checks in transparent awaits #133023

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
148 changes: 66 additions & 82 deletions ...oreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncHelpers.CoreCLR.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -435,64 +435,30 @@ private static unsafe T Suspend<T>(Task<T> task, ConfigureAwaitOptions options)
return default!;
}

/// <summary>
/// Used by internal thunks that implement awaiting on ValueTask.
/// A ValueTask may wrap:
/// - Completed result (we never await this)
/// - Task
/// - ValueTaskSource
/// Therefore, when we are awaiting a ValueTask completion we are really
/// awaiting a completion of an underlying Task or ValueTaskSource.
/// </summary>
/// <param name="valueTask">ValueTask whose completion we are awaiting.</param>
[Intrinsic]
[BypassReadyToRun]
[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.Async)]
private static unsafe void TransparentSuspend(ValueTask valueTask)
private static unsafe void TransparentSuspend(IValueTaskSource source, short token)
{
ref RuntimeAsyncAwaitState state = ref t_runtimeAsyncAwaitState;
Continuation? sentinelContinuation = state.SentinelContinuation ??= new Continuation();

Continuation nextCont;
object? obj = valueTask._obj;
if (obj is Task t)
ValueTaskSourceContinuation? vtsCont = state.CachedValueTaskSourceContinuation;
if (vtsCont != null)
{
RuntimeAsyncTaskContinuation? taskCont = state.CachedTaskContinuation;
if (taskCont != null)
{
state.CachedTaskContinuation = null;
}
else
{
taskCont = new RuntimeAsyncTaskContinuation();
}

taskCont.Initialize(t);
state.StackState->TaskContinuation = taskCont;
nextCont = taskCont;
state.CachedValueTaskSourceContinuation = null;
}
else
{
ValueTaskSourceContinuation? vtsCont = state.CachedValueTaskSourceContinuation;
if (vtsCont != null)
{
state.CachedValueTaskSourceContinuation = null;
}
else
{
vtsCont = new ValueTaskSourceContinuation();
}

Debug.Assert(obj is IValueTaskSource);
vtsCont.Initialize(Unsafe.As<object, IValueTaskSource>(ref obj), valueTask._token);
state.StackState->ValueTaskSourceContinuation = vtsCont;
nextCont = vtsCont;
vtsCont = new ValueTaskSourceContinuation();
}

sentinelContinuation.Next = nextCont;
vtsCont.Initialize(source, token);

sentinelContinuation.Next = vtsCont;
state.StackState->ValueTaskSourceContinuation = vtsCont;
state.CaptureContexts();
AsyncSuspend(nextCont);
AsyncSuspend(vtsCont);
}

[Intrinsic]
Expand Down Expand Up @@ -536,50 +502,27 @@ private static unsafe void Suspend(IValueTaskSource source, short token, bool co
[Intrinsic]
[BypassReadyToRun]
[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.Async)]
private static unsafe T TransparentSuspend<T>(ValueTask<T> valueTask)
private static unsafe T TransparentSuspend<T>(IValueTaskSource<T> source, short token)
{
ref RuntimeAsyncAwaitState state = ref t_runtimeAsyncAwaitState;
Continuation? sentinelContinuation = state.SentinelContinuation ??= new Continuation();

Continuation nextCont;
object? obj = valueTask._obj;
if (obj is Task<T> t)
ValueTaskSourceContinuation? vtsCont = state.CachedValueTaskSourceContinuation;
if (vtsCont != null)
{
RuntimeAsyncTaskContinuation? taskCont = state.CachedTaskContinuation;
if (taskCont != null)
{
state.CachedTaskContinuation = null;
}
else
{
taskCont = new RuntimeAsyncTaskContinuation();
}

taskCont.Initialize<T>(t);
state.StackState->TaskContinuation = taskCont;
nextCont = taskCont;
state.CachedValueTaskSourceContinuation = null;
}
else
{
ValueTaskSourceContinuation? vtsCont = state.CachedValueTaskSourceContinuation;
if (vtsCont != null)
{
state.CachedValueTaskSourceContinuation = null;
}
else
{
vtsCont = new ValueTaskSourceContinuation();
}

Debug.Assert(obj is IValueTaskSource<T>);
vtsCont.Initialize<T>(Unsafe.As<object, IValueTaskSource<T>>(ref obj), valueTask._token);
state.StackState->ValueTaskSourceContinuation = vtsCont;
nextCont = vtsCont;
vtsCont = new ValueTaskSourceContinuation();
}

sentinelContinuation.Next = nextCont;
vtsCont.Initialize<T>(source, token);

sentinelContinuation.Next = vtsCont;
state.StackState->ValueTaskSourceContinuation = vtsCont;
state.CaptureContexts();
AsyncSuspend(nextCont);
AsyncSuspend(vtsCont);
return default!;
}

Expand Down Expand Up @@ -706,14 +649,35 @@ private static void TransparentAwait(Task task)
[MethodImpl(MethodImplOptions.Async)]
private static void TransparentAwait(ValueTask task)
{
if (!task.IsCompleted)
object? obj = task._obj;
if (obj == null)
{
return;
}

if (obj is Task t)
{
if (!t.IsCompleted)
{
TailAwait();
TransparentSuspend(t);
return;
}

TaskAwaiter.ValidateEnd(t);
return;
}

Debug.Assert(obj is IValueTaskSource);
IValueTaskSource vts = Unsafe.As<object, IValueTaskSource>(ref obj);
if (vts.GetStatus(task._token) == ValueTaskSourceStatus.Pending)
{
TailAwait();
TransparentSuspend(task);
TransparentSuspend(vts, task._token);
return;
}

task.ThrowIfCompletedUnsuccessfully();
vts.GetResult(task._token);
}

[BypassReadyToRun]
Expand All @@ -734,13 +698,33 @@ private static T TransparentAwait<T>(Task<T> task)
[MethodImpl(MethodImplOptions.Async)]
private static T TransparentAwait<T>(ValueTask<T> task)
{
if (!task.IsCompleted)
object? obj = task._obj;
if (obj == null)
{
return task._result!;
}

if (obj is Task<T> t)
{
if (!t.IsCompleted)
{
TailAwait();
return TransparentSuspend(t);
}

TaskAwaiter.ValidateEnd(t);
return t.ResultOnSuccess;
}

Debug.Assert(obj is IValueTaskSource<T>);
IValueTaskSource<T> vts = Unsafe.As<object, IValueTaskSource<T>>(ref obj);
if (vts.GetStatus(task._token) == ValueTaskSourceStatus.Pending)
{
TailAwait();
return TransparentSuspend(task);
return TransparentSuspend(vts, task._token);
}

return task.Result;
return vts.GetResult(task._token);
}

// Represents execution of a chain of suspended and resuming runtime
Expand Down
Loading