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ProcessReaper.cs
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ProcessReaper.cs
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
#nullable enable
using System.Diagnostics;
using Microsoft.Win32.SafeHandles;
namespace Microsoft.DotNet.Cli.Utils
{
/// <summary>
/// Responsible for reaping a target process if the current process terminates.
/// </summary>
/// <remarks>
/// On Windows, a job object will be used to ensure the termination of the target
/// process (and its tree) even if the current process is rudely terminated.
///
/// On POSIX systems, the reaper will handle SIGTERM and attempt to forward the
/// signal to the target process only.
///
/// The reaper also suppresses SIGINT in the current process to allow the target
/// process to handle the signal.
/// </remarks>
internal class ProcessReaper : IDisposable
{
/// <summary>
/// Creates a new process reaper.
/// </summary>
/// <param name="process">The target process to reap if the current process terminates. The process should not yet be started.</param>
public ProcessReaper(Process process)
{
_process = process;
// The tests need the event handlers registered prior to spawning the child to prevent a race
// where the child writes output the test expects before the intermediate dotnet process
// has registered the event handlers to handle the signals the tests will generate.
Console.CancelKeyPress += HandleCancelKeyPress;
if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
_shutdownMutex = new Mutex();
AppDomain.CurrentDomain.ProcessExit += HandleProcessExit;
}
}
/// <summary>
/// Call to notify the reaper that the process has started.
/// </summary>
public void NotifyProcessStarted()
{
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
// Limit the use of job objects to versions of Windows that support nested jobs (i.e. Windows 8/2012 or later).
// Ideally, we would check for some new API export or OS feature instead of the OS version,
// but nested jobs are transparently implemented with respect to the Job Objects API.
// Note: Windows 8.1 and later may report as Windows 8 (see https://docs.microsoft.com/en-us/windows/desktop/sysinfo/operating-system-version).
// However, for the purpose of this check that is still sufficient.
if (Environment.OSVersion.Version.Major > 6 ||
(Environment.OSVersion.Version.Major == 6 && Environment.OSVersion.Version.Minor >= 2))
{
_job = AssignProcessToJobObject(_process.Handle);
}
}
}
public void Dispose()
{
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
if (_job != null)
{
// Clear the kill on close flag because the child process terminated successfully
// If this fails, then we have no choice but to terminate any remaining processes in the job
SetKillOnJobClose(_job.DangerousGetHandle(), false);
_job.Dispose();
_job = null;
}
}
else
{
AppDomain.CurrentDomain.ProcessExit -= HandleProcessExit;
// If there's been a shutdown via the process exit handler,
// this will block the current thread so we don't race with the CLR shutdown
// from the signal handler.
if (_shutdownMutex != null)
{
_shutdownMutex.WaitOne();
_shutdownMutex.ReleaseMutex();
_shutdownMutex.Dispose();
_shutdownMutex = null;
}
}
Console.CancelKeyPress -= HandleCancelKeyPress;
}
private static void HandleCancelKeyPress(object? sender, ConsoleCancelEventArgs e)
{
// Ignore SIGINT/SIGQUIT so that the process can handle the signal
e.Cancel = true;
}
private static SafeWaitHandle? AssignProcessToJobObject(IntPtr process)
{
var job = NativeMethods.Windows.CreateJobObjectW(IntPtr.Zero, null);
if (job == null || job.IsInvalid)
{
return null;
}
if (!SetKillOnJobClose(job.DangerousGetHandle(), true))
{
job.Dispose();
return null;
}
if (!NativeMethods.Windows.AssignProcessToJobObject(job.DangerousGetHandle(), process))
{
job.Dispose();
return null;
}
return job;
}
private void HandleProcessExit(object? sender, EventArgs args)
{
int processId;
try
{
processId = _process.Id;
}
catch (InvalidOperationException)
{
// The process hasn't started yet; nothing to signal
return;
}
// Take ownership of the shutdown mutex; this will ensure that the other
// thread also waiting on the process to exit won't complete CLR shutdown before
// this one does.
_shutdownMutex?.WaitOne();
if (!_process.WaitForExit(0) && NativeMethods.Posix.kill(processId, NativeMethods.Posix.SIGTERM) != 0)
{
// Couldn't send the signal, don't wait
return;
}
// If SIGTERM was ignored by the target, then we'll still wait
_process.WaitForExit();
Environment.ExitCode = _process.ExitCode;
}
private static bool SetKillOnJobClose(IntPtr job, bool value)
{
var information = new NativeMethods.Windows.JobObjectExtendedLimitInformation
{
BasicLimitInformation = new NativeMethods.Windows.JobObjectBasicLimitInformation
{
LimitFlags = (value ? NativeMethods.Windows.JobObjectLimitFlags.JobObjectLimitKillOnJobClose : 0)
}
};
var length = Marshal.SizeOf(typeof(NativeMethods.Windows.JobObjectExtendedLimitInformation));
var informationPtr = Marshal.AllocHGlobal(length);
try
{
Marshal.StructureToPtr(information, informationPtr, false);
if (!NativeMethods.Windows.SetInformationJobObject(
job,
NativeMethods.Windows.JobObjectInfoClass.JobObjectExtendedLimitInformation,
informationPtr,
(uint)length))
{
return false;
}
return true;
}
finally
{
Marshal.FreeHGlobal(informationPtr);
}
}
private Process _process;
private SafeWaitHandle? _job;
private Mutex? _shutdownMutex;
}
}