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[C#] Remove unnecessary SemaphoreSlim locks for handler fields #625

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Merged
stephentoub merged 2 commits into from
Mar 2, 2026
+7 −51
Merged

[C#] Remove unnecessary SemaphoreSlim locks for handler fields #625

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f556505
Initial plan
Copilot Mar 2, 2026
d555dc6
Remove unnecessary SemaphoreSlims for _permissionHandlerLock and _use…
Copilot Mar 2, 2026
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58 changes: 7 additions & 51 deletions dotnet/src/Session.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -47,10 +47,8 @@ public partial class CopilotSession : IAsyncDisposable
private readonly HashSet<SessionEventHandler> _eventHandlers = new();
private readonly Dictionary<string, AIFunction> _toolHandlers = new();
private readonly JsonRpc _rpc;
private PermissionRequestHandler? _permissionHandler;
private readonly SemaphoreSlim _permissionHandlerLock = new(1, 1);
private UserInputHandler? _userInputHandler;
private readonly SemaphoreSlim _userInputHandlerLock = new(1, 1);
private volatile PermissionRequestHandler? _permissionHandler;
private volatile UserInputHandler? _userInputHandler;
private SessionHooks? _hooks;
private readonly SemaphoreSlim _hooksLock = new(1, 1);
private SessionRpc? _sessionRpc;
Expand Down Expand Up @@ -300,15 +298,7 @@ internal void RegisterTools(ICollection<AIFunction> tools)
/// </remarks>
internal void RegisterPermissionHandler(PermissionRequestHandler handler)
{
_permissionHandlerLock.Wait();
try
{
_permissionHandler = handler;
}
finally
{
_permissionHandlerLock.Release();
}
_permissionHandler = handler;
}

/// <summary>
Expand All @@ -318,16 +308,7 @@ internal void RegisterPermissionHandler(PermissionRequestHandler handler)
/// <returns>A task that resolves with the permission decision.</returns>
internal async Task<PermissionRequestResult> HandlePermissionRequestAsync(JsonElement permissionRequestData)
{
await _permissionHandlerLock.WaitAsync();
PermissionRequestHandler? handler;
try
{
handler = _permissionHandler;
}
finally
{
_permissionHandlerLock.Release();
}
var handler = _permissionHandler;

if (handler == null)
{
Expand All @@ -354,15 +335,7 @@ internal async Task<PermissionRequestResult> HandlePermissionRequestAsync(JsonEl
/// <param name="handler">The handler to invoke when user input is requested.</param>
internal void RegisterUserInputHandler(UserInputHandler handler)
{
_userInputHandlerLock.Wait();
try
{
_userInputHandler = handler;
}
finally
{
_userInputHandlerLock.Release();
}
_userInputHandler = handler;
}

/// <summary>
Expand All @@ -372,16 +345,7 @@ internal void RegisterUserInputHandler(UserInputHandler handler)
/// <returns>A task that resolves with the user's response.</returns>
internal async Task<UserInputResponse> HandleUserInputRequestAsync(UserInputRequest request)
{
await _userInputHandlerLock.WaitAsync();
UserInputHandler? handler;
try
{
handler = _userInputHandler;
}
finally
{
_userInputHandlerLock.Release();
}
var handler = _userInputHandler;

if (handler == null)
{
Expand Down Expand Up @@ -589,15 +553,7 @@ await InvokeRpcAsync<object>(
_eventHandlers.Clear();
_toolHandlers.Clear();

await _permissionHandlerLock.WaitAsync();
try
{
_permissionHandler = null;
}
finally
{
_permissionHandlerLock.Release();
}
_permissionHandler = null;
}

private class OnDisposeCall(Action callback) : IDisposable
Expand Down