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Fix deadlock if an MSBuild task is writing to stdout #78927

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merged 1 commit into from
Jun 12, 2025
Merged

Fix deadlock if an MSBuild task is writing to stdout #78927

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13 changes: 9 additions & 4 deletions src/Workspaces/MSBuild/Core/MSBuild/BuildHostProcessManager.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -398,7 +398,8 @@ public BuildHostProcess(Process process, string pipeName, ILoggerFactory? logger
_process.EnableRaisingEvents = true;
_process.Exited += Process_Exited;

_process.ErrorDataReceived += Process_ErrorDataReceived;
_process.OutputDataReceived += (_, e) => LogProcessOutput(e, "stdout");
_process.ErrorDataReceived += (_, e) => LogProcessOutput(e, "stderr");

var pipeClient = NamedPipeUtil.CreateClient(".", pipeName, PipeDirection.InOut, PipeOptions.Asynchronous);
pipeClient.Connect(TimeOutMsNewProcess);
Expand All @@ -412,7 +413,11 @@ public BuildHostProcess(Process process, string pipeName, ILoggerFactory? logger
_rpcClient.Disconnected += Process_Exited;
BuildHost = new RemoteBuildHost(_rpcClient);

// Call this last so our type is fully constructed before we start firing events
// Close the standard input stream so that if any build tasks were to try reading from the console, they won't deadlock waiting for input.
_process.StandardInput.Close();

// Call Begin*ReadLine methods last so so our type is fully constructed before we start firing events.
_process.BeginOutputReadLine();
_process.BeginErrorReadLine();
}

Expand All @@ -421,14 +426,14 @@ private void Process_Exited(object? sender, EventArgs e)
Disconnected?.Invoke(this, EventArgs.Empty);
}

private void Process_ErrorDataReceived(object sender, DataReceivedEventArgs e)
private void LogProcessOutput(DataReceivedEventArgs e, string outputName)
{
if (e.Data is not null)
{
lock (_processLogMessages)
_processLogMessages.AppendLine(e.Data);

_logger?.LogTrace($"Message from Process: {e.Data}");
_logger?.LogTrace($"Message on {outputName}: {e.Data}");
}
}

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