|
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.IO.Pipes;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System.Security.Principal;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Roslyn.Utilities;
using static Microsoft.CodeAnalysis.CommandLine.NativeMethods;
namespace Microsoft.CodeAnalysis.CommandLine
{
internal sealed class BuildServerConnection
{
/// <summary>
/// The time to wait for a named pipe connection to complete to an existing server
/// process.
/// </summary>
/// <remarks>
/// The compiler server is designed to be responsive to new connections so in ideal
/// circumstances a timeout as short as one second is fine. However, in practice the
/// server can become temporarily unresponsive if say the machine is under heavy load
/// or a connection occurs just as a gen2 GC occurs.
///
/// In any of these cases abandoning the connection attempt means falling back to
/// starting csc.exe / vbc.exe which will likely make the above problems. That will
/// create a new process that adds more load to the system.
///
/// As such this timeout should be significantly longer than the average gen2 pause
/// time for the server. When changing this value consider profiling building
/// Roslyn.sln and consulting the GC stats to see what a typical pause time is.
/// </remarks>
internal const int TimeOutMsExistingProcess = 5_000;
/// <summary>
/// The time to wait for a named pipe connection to complete for a newly started server
/// </summary>
internal const int TimeOutMsNewProcess = 20_000;
// To share a mutex between processes the name should have the Global prefix
private const string GlobalMutexPrefix = "Global\\";
/// <summary>
/// Determines if the compiler server is supported in this environment.
/// </summary>
internal static bool IsCompilerServerSupported => GetPipeName("") is object;
/// <summary>
/// Create a build request for processing on the server.
/// </summary>
internal static BuildRequest CreateBuildRequest(
string requestId,
RequestLanguage language,
List<string> arguments,
string workingDirectory,
string? tempDirectory,
string? keepAlive,
string? libDirectory)
{
Debug.Assert(workingDirectory is object);
return BuildRequest.Create(
language,
arguments,
workingDirectory: workingDirectory,
tempDirectory: tempDirectory,
compilerHash: BuildProtocolConstants.GetCommitHash() ?? "",
requestId: requestId,
keepAlive: keepAlive,
libDirectory: libDirectory);
}
/// <summary>
/// Shutting down the server is an inherently racy operation. The server can be started or stopped by
/// external parties at any time.
///
/// This function will return success if at any time in the function the server is determined to no longer
/// be running.
/// </summary>
internal static async Task<bool> RunServerShutdownRequestAsync(
string pipeName,
int? timeoutOverride,
bool waitForProcess,
ICompilerServerLogger logger,
CancellationToken cancellationToken)
{
if (wasServerRunning(pipeName) == false)
{
// The server holds the mutex whenever it is running, if it's not open then the
// server simply isn't running.
return true;
}
try
{
var request = BuildRequest.CreateShutdown();
// Don't create the server when sending a shutdown request. That would defeat the
// purpose a bit.
var response = await RunServerBuildRequestAsync(
request,
pipeName,
timeoutOverride,
tryCreateServerFunc: (_, _) => false,
logger,
cancellationToken).ConfigureAwait(false);
if (response is ShutdownBuildResponse shutdownBuildResponse)
{
if (waitForProcess)
{
try
{
var process = Process.GetProcessById(shutdownBuildResponse.ServerProcessId);
#if NET5_0_OR_GREATER
await process.WaitForExitAsync(cancellationToken).ConfigureAwait(false);
#else
process.WaitForExit();
#endif
}
catch (Exception)
{
// There is an inherent race here with the server process. If it has already shutdown
// by the time we try to access it then the operation has succeed.
}
}
return true;
}
return wasServerRunning(pipeName) == false;
}
catch (Exception)
{
// If the server was in the process of shutting down when we connected then it's reasonable
// for an exception to happen. If the mutex has shutdown at this point then the server
// is shut down.
return wasServerRunning(pipeName) == false;
}
// Was a server running with the specified session key during the execution of this call?
static bool? wasServerRunning(string pipeName)
{
string mutexName = GetServerMutexName(pipeName);
return WasServerMutexOpen(mutexName);
}
}
internal static Task<BuildResponse> RunServerBuildRequestAsync(
BuildRequest buildRequest,
string pipeName,
string clientDirectory,
ICompilerServerLogger logger,
CancellationToken cancellationToken)
=> RunServerBuildRequestAsync(
buildRequest,
pipeName,
timeoutOverride: null,
tryCreateServerFunc: (pipeName, logger) => TryCreateServer(clientDirectory, pipeName, logger, out int _),
logger,
cancellationToken);
internal static async Task<BuildResponse> RunServerBuildRequestAsync(
BuildRequest buildRequest,
string pipeName,
int? timeoutOverride,
Func<string, ICompilerServerLogger, bool> tryCreateServerFunc,
ICompilerServerLogger logger,
CancellationToken cancellationToken)
{
Debug.Assert(pipeName is object);
// early check for the build hash. If we can't find it something is wrong; no point even trying to go to the server
if (string.IsNullOrWhiteSpace(BuildProtocolConstants.GetCommitHash()))
{
return new IncorrectHashBuildResponse();
}
using var pipe = await tryConnectToServerAsync(pipeName, timeoutOverride, logger, tryCreateServerFunc, cancellationToken).ConfigureAwait(false);
if (pipe is null)
{
return new CannotConnectResponse();
}
else
{
return await tryRunRequestAsync(pipe, buildRequest, logger, cancellationToken).ConfigureAwait(false);
}
// This code uses a Mutex.WaitOne / ReleaseMutex pairing. Both of these calls must occur on the same thread
// or an exception will be thrown. This code lives in a separate non-async function to help ensure this
// invariant doesn't get invalidated in the future by an `await` being inserted.
static Task<NamedPipeClientStream?> tryConnectToServerAsync(
string pipeName,
int? timeoutOverride,
ICompilerServerLogger logger,
Func<string, ICompilerServerLogger, bool> tryCreateServerFunc,
CancellationToken cancellationToken)
{
var originalThreadId = Environment.CurrentManagedThreadId;
var timeoutNewProcess = timeoutOverride ?? TimeOutMsNewProcess;
var timeoutExistingProcess = timeoutOverride ?? TimeOutMsExistingProcess;
IServerMutex? clientMutex = null;
try
{
var holdsMutex = false;
try
{
var clientMutexName = GetClientMutexName(pipeName);
clientMutex = OpenOrCreateMutex(clientMutexName, out holdsMutex);
}
catch
{
// The Mutex constructor can throw in certain cases. One specific example is docker containers
// where the /tmp directory is restricted. In those cases there is no reliable way to execute
// the server and we need to fall back to the command line.
//
// Example: https://github.com/dotnet/roslyn/issues/24124
return Task.FromResult<NamedPipeClientStream?>(null);
}
if (!holdsMutex)
{
try
{
holdsMutex = clientMutex.TryLock(timeoutNewProcess);
if (!holdsMutex)
{
return Task.FromResult<NamedPipeClientStream?>(null);
}
}
catch (AbandonedMutexException)
{
holdsMutex = true;
}
}
// Check for an already running server
var serverMutexName = GetServerMutexName(pipeName);
bool wasServerRunning = WasServerMutexOpen(serverMutexName);
var timeout = wasServerRunning ? timeoutExistingProcess : timeoutNewProcess;
if (wasServerRunning || tryCreateServerFunc(pipeName, logger))
{
return TryConnectToServerAsync(pipeName, timeout, logger, cancellationToken);
}
else
{
return Task.FromResult<NamedPipeClientStream?>(null);
}
}
finally
{
try
{
clientMutex?.Dispose();
}
catch (ApplicationException e)
{
var releaseThreadId = Environment.CurrentManagedThreadId;
var message = $"ReleaseMutex failed. WaitOne Id: {originalThreadId} Release Id: {releaseThreadId}";
throw new Exception(message, e);
}
}
}
// Try and run the given BuildRequest on the server. If the request cannot be run then
// an appropriate error response will be returned.
static async Task<BuildResponse> tryRunRequestAsync(
NamedPipeClientStream pipeStream,
BuildRequest request,
ICompilerServerLogger logger,
CancellationToken cancellationToken)
{
try
{
logger.Log($"Begin writing request for {request.RequestId}");
await request.WriteAsync(pipeStream, cancellationToken).ConfigureAwait(false);
logger.Log($"End writing request for {request.RequestId}");
}
catch (Exception e)
{
logger.LogException(e, $"Error writing build request for {request.RequestId}");
return new RejectedBuildResponse($"Error writing build request: {e.Message}");
}
// Wait for the compilation and a monitor to detect if the server disconnects
var serverCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
logger.Log($"Begin reading response for {request.RequestId}");
var responseTask = BuildResponse.ReadAsync(pipeStream, serverCts.Token);
var monitorTask = MonitorDisconnectAsync(pipeStream, request.RequestId, logger, serverCts.Token);
await Task.WhenAny(responseTask, monitorTask).ConfigureAwait(false);
logger.Log($"End reading response for {request.RequestId}");
BuildResponse response;
if (responseTask.IsCompleted)
{
// await the task to log any exceptions
try
{
response = await responseTask.ConfigureAwait(false);
}
catch (Exception e)
{
logger.LogException(e, $"Reading response for {request.RequestId}");
response = new RejectedBuildResponse($"Error reading response: {e.Message}");
}
}
else
{
logger.LogError($"Client disconnect for {request.RequestId}");
response = new RejectedBuildResponse($"Client disconnected");
}
// Cancel whatever task is still around
serverCts.Cancel();
RoslynDebug.Assert(response != null);
return response;
}
}
/// <summary>
/// The IsConnected property on named pipes does not detect when the client has disconnected
/// if we don't attempt any new I/O after the client disconnects. We start an async I/O here
/// which serves to check the pipe for disconnection.
/// </summary>
internal static async Task MonitorDisconnectAsync(
PipeStream pipeStream,
string requestId,
ICompilerServerLogger logger,
CancellationToken cancellationToken = default)
{
var buffer = Array.Empty<byte>();
while (!cancellationToken.IsCancellationRequested && pipeStream.IsConnected)
{
try
{
// Wait a tenth of a second before trying again
await Task.Delay(millisecondsDelay: 100, cancellationToken).ConfigureAwait(false);
await pipeStream.ReadAsync(buffer, 0, 0, cancellationToken).ConfigureAwait(false);
}
catch (OperationCanceledException)
{
}
catch (Exception e)
{
// It is okay for this call to fail. Errors will be reflected in the
// IsConnected property which will be read on the next iteration of the
logger.LogException(e, $"Error poking pipe {requestId}.");
}
}
}
/// <summary>
/// Attempt to connect to the server and return a null <see cref="NamedPipeClientStream"/> if connection
/// failed. This method will throw on cancellation.
/// </summary>
internal static async Task<NamedPipeClientStream?> TryConnectToServerAsync(
string pipeName,
int timeoutMs,
ICompilerServerLogger logger,
CancellationToken cancellationToken)
{
NamedPipeClientStream? pipeStream = null;
try
{
// Machine-local named pipes are named "\\.\pipe\<pipename>".
// We use the SHA1 of the directory the compiler exes live in as the pipe name.
// The NamedPipeClientStream class handles the "\\.\pipe\" part for us.
logger.Log("Attempt to open named pipe '{0}'", pipeName);
pipeStream = NamedPipeUtil.CreateClient(".", pipeName, PipeDirection.InOut, PipeOptions.Asynchronous);
cancellationToken.ThrowIfCancellationRequested();
logger.Log("Attempt to connect named pipe '{0}'", pipeName);
try
{
// NamedPipeClientStream.ConnectAsync on the "full" framework has a bug where it
// tries to move potentially expensive work (actually connecting to the pipe) to
// a background thread with Task.Factory.StartNew. However, that call will merely
// queue the work onto the TaskScheduler associated with the "current" Task which
// does not guarantee it will be processed on a background thread and this could
// lead to a hang.
// To avoid this, we first force ourselves to a background thread using Task.Run.
// This ensures that the Task created by ConnectAsync will run on the default
// TaskScheduler (i.e., on a threadpool thread) which was the intent all along.
await Task.Run(() => pipeStream.ConnectAsync(timeoutMs, cancellationToken), cancellationToken).ConfigureAwait(false);
}
catch (Exception e) when (e is IOException || e is TimeoutException)
{
// Note: IOException can also indicate timeout. From docs:
// TimeoutException: Could not connect to the server within the
// specified timeout period.
// IOException: The server is connected to another client and the
// time-out period has expired.
logger.LogException(e, $"Connecting to server timed out after {timeoutMs} ms");
pipeStream.Dispose();
return null;
}
logger.Log("Named pipe '{0}' connected", pipeName);
cancellationToken.ThrowIfCancellationRequested();
// Verify that we own the pipe.
if (!NamedPipeUtil.CheckPipeConnectionOwnership(pipeStream))
{
pipeStream.Dispose();
logger.LogError("Owner of named pipe is incorrect");
return null;
}
return pipeStream;
}
catch (Exception e) when (!(e is TaskCanceledException || e is OperationCanceledException))
{
logger.LogException(e, "Exception while connecting to process");
pipeStream?.Dispose();
return null;
}
}
internal static (string processFilePath, string commandLineArguments, string toolFilePath) GetServerProcessInfo(string clientDir, string pipeName)
{
var serverPathWithoutExtension = Path.Combine(clientDir, "VBCSCompiler");
var commandLineArgs = $@"""-pipename:{pipeName}""";
return RuntimeHostInfo.GetProcessInfo(serverPathWithoutExtension, commandLineArgs);
}
/// <summary>
/// This will attempt to start a compiler server process using the executable inside the
/// directory <paramref name="clientDirectory"/>. This returns "true" if starting the
/// compiler server process was successful, it does not state whether the server successfully
/// started or not (it could crash on startup).
/// </summary>
internal static bool TryCreateServer(string clientDirectory, string pipeName, ICompilerServerLogger logger, out int processId)
{
processId = 0;
var serverInfo = GetServerProcessInfo(clientDirectory, pipeName);
if (!File.Exists(serverInfo.toolFilePath))
{
return false;
}
if (PlatformInformation.IsWindows)
{
// As far as I can tell, there isn't a way to use the Process class to
// create a process with no stdin/stdout/stderr, so we use P/Invoke.
// This code was taken from MSBuild task starting code.
STARTUPINFO startInfo = new STARTUPINFO();
startInfo.cb = Marshal.SizeOf(startInfo);
startInfo.hStdError = InvalidIntPtr;
startInfo.hStdInput = InvalidIntPtr;
startInfo.hStdOutput = InvalidIntPtr;
startInfo.dwFlags = STARTF_USESTDHANDLES;
uint dwCreationFlags = NORMAL_PRIORITY_CLASS | CREATE_NO_WINDOW;
PROCESS_INFORMATION processInfo;
logger.Log("Attempting to create process '{0}'", serverInfo.processFilePath);
var builder = new StringBuilder($@"""{serverInfo.processFilePath}"" {serverInfo.commandLineArguments}");
bool success = CreateProcess(
lpApplicationName: null,
lpCommandLine: builder,
lpProcessAttributes: NullPtr,
lpThreadAttributes: NullPtr,
bInheritHandles: false,
dwCreationFlags: dwCreationFlags,
lpEnvironment: NullPtr, // Inherit environment
lpCurrentDirectory: clientDirectory,
lpStartupInfo: ref startInfo,
lpProcessInformation: out processInfo);
if (success)
{
logger.Log("Successfully created process with process id {0}", processInfo.dwProcessId);
CloseHandle(processInfo.hProcess);
CloseHandle(processInfo.hThread);
processId = processInfo.dwProcessId;
}
else
{
logger.LogError("Failed to create process. GetLastError={0}", Marshal.GetLastWin32Error());
}
return success;
}
else
{
try
{
var startInfo = new ProcessStartInfo()
{
FileName = serverInfo.processFilePath,
Arguments = serverInfo.commandLineArguments,
UseShellExecute = false,
WorkingDirectory = clientDirectory,
RedirectStandardInput = true,
RedirectStandardOutput = true,
RedirectStandardError = true,
CreateNoWindow = true
};
if (Process.Start(startInfo) is { } process)
{
processId = process.Id;
return true;
}
else
{
return false;
}
}
catch
{
return false;
}
}
}
/// <returns>
/// Null if not enough information was found to create a valid pipe name.
/// </returns>
internal static string GetPipeName(string clientDirectory)
{
// Prefix with username and elevation
bool isAdmin = false;
if (PlatformInformation.IsWindows)
{
#pragma warning disable CA1416 // Validate platform compatibility
var currentIdentity = WindowsIdentity.GetCurrent();
var principal = new WindowsPrincipal(currentIdentity);
isAdmin = principal.IsInRole(WindowsBuiltInRole.Administrator);
#pragma warning restore CA1416
}
var userName = Environment.UserName;
return GetPipeName(userName, isAdmin, clientDirectory);
}
internal static string GetPipeName(
string userName,
bool isAdmin,
string clientDirectory)
{
// Normalize away trailing slashes. File APIs include / exclude this with no
// discernable pattern. Easiest to normalize it here vs. auditing every caller
// of this method.
clientDirectory = clientDirectory.TrimEnd(Path.DirectorySeparatorChar);
// Similarly, we don't want multiple servers if the provided launch path differs in casing.
clientDirectory = clientDirectory.ToLowerInvariant();
var pipeNameInput = $"{userName}.{isAdmin}.{clientDirectory}";
using (var sha = SHA256.Create())
{
var bytes = sha.ComputeHash(Encoding.UTF8.GetBytes(pipeNameInput));
return Convert.ToBase64String(bytes)
.Replace("/", "_")
.Replace("=", string.Empty);
}
}
internal static bool WasServerMutexOpen(string mutexName)
{
try
{
if (PlatformInformation.IsUsingMonoRuntime)
{
using var mutex = new ServerFileMutex(mutexName);
return !mutex.CouldLock();
}
else
{
return ServerNamedMutex.WasOpen(mutexName);
}
}
catch
{
// In the case an exception occurred trying to open the Mutex then
// the assumption is that it's not open.
return false;
}
}
internal static IServerMutex OpenOrCreateMutex(string name, out bool createdNew)
{
if (PlatformInformation.IsUsingMonoRuntime)
{
var mutex = new ServerFileMutex(name);
createdNew = mutex.TryLock(0);
return mutex;
}
else
{
return new ServerNamedMutex(name, out createdNew);
}
}
internal static string GetServerMutexName(string pipeName)
{
return $"{GlobalMutexPrefix}{pipeName}.server";
}
internal static string GetClientMutexName(string pipeName)
{
return $"{GlobalMutexPrefix}{pipeName}.client";
}
}
internal interface IServerMutex : IDisposable
{
bool TryLock(int timeoutMs);
bool IsDisposed { get; }
}
/// <summary>
/// An interprocess mutex abstraction based on file sharing permission (FileShare.None).
/// If multiple processes running as the same user create FileMutex instances with the same name,
/// those instances will all point to the same file somewhere in a selected temporary directory.
/// The TryLock method can be used to attempt to acquire the mutex, with Dispose used to release.
/// The CouldLock method can be used to check whether an attempt to acquire the mutex would have
/// succeeded at the current time, without actually acquiring it.
/// Unlike Win32 named mutexes, there is no mechanism for detecting an abandoned mutex. The file
/// will simply revert to being unlocked but remain where it is.
/// </summary>
internal sealed class ServerFileMutex : IServerMutex
{
public FileStream? Stream;
public readonly string FilePath;
public readonly string GuardPath;
public bool IsDisposed { get; private set; }
internal static string GetMutexDirectory()
{
var tempPath = Path.GetTempPath();
var result = Path.Combine(tempPath!, ".roslyn");
Directory.CreateDirectory(result);
return result;
}
public ServerFileMutex(string name)
{
var mutexDirectory = GetMutexDirectory();
FilePath = Path.Combine(mutexDirectory, name);
GuardPath = Path.Combine(mutexDirectory, ".guard");
}
/// <summary>
/// Acquire the guard by opening the guard file with FileShare.None. The guard must only ever
/// be held for very brief amounts of time, so we can simply spin until it is acquired. The
/// guard must be released by disposing the FileStream returned from this routine. Note the
/// guard file is never deleted; this is a leak, but only of a single file.
/// </summary>
internal FileStream LockGuard()
{
// We should be able to acquire the guard quickly. Limit the number of retries anyway
// by some arbitrary bound to avoid getting hung up in a possibly infinite loop.
for (var i = 0; i < 100; i++)
{
try
{
return new FileStream(GuardPath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);
}
catch (IOException)
{
// Guard currently held by someone else.
// We want to sleep for a short period of time to ensure that other processes
// have an opportunity to finish their work and relinquish the lock.
// Spinning here (via Yield) would work but risks creating a priority
// inversion if the lock is held by a lower-priority process.
Thread.Sleep(1);
}
}
// Handle unexpected failure to acquire guard as error.
throw new InvalidOperationException("Unable to acquire guard");
}
/// <summary>
/// Attempt to acquire the lock by opening the lock file with FileShare.None. Sets "Stream"
/// and returns true if successful, returns false if the lock is already held by another
/// thread or process. Guard must be held when calling this routine.
/// </summary>
internal bool TryLockFile()
{
Debug.Assert(Stream is null);
FileStream? stream = null;
try
{
stream = new FileStream(FilePath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);
// On some targets, the file locking used to implement FileShare.None may not be
// atomic with opening/creating the file. This creates a race window when another
// thread holds the lock and is just about to unlock: we may be able to open the
// file here, then the other thread unlocks and deletes the file, and then we
// acquire the lock on our file handle - but the actual file is already deleted.
// To close this race, we verify that the file does in fact still exist now that
// we have successfully acquired the locked FileStream. (Note that this check is
// safe because we cannot race with an other attempt to create the file since we
// hold the guard, and after the FileStream constructor returned we can no race
// with file deletion because we hold the lock.)
if (!File.Exists(FilePath))
{
// To simplify the logic, we treat this case as "unable to acquire the lock"
// because it we caught another process while it owned the lock and was just
// giving it up. If the caller retries, we'll likely acquire the lock then.
stream.Dispose();
return false;
}
}
catch (Exception)
{
stream?.Dispose();
return false;
}
Stream = stream;
return true;
}
/// <summary>
/// Release the lock by deleting the lock file and disposing "Stream".
/// </summary>
internal void UnlockFile()
{
Debug.Assert(Stream is not null);
try
{
// Delete the lock file while the stream is not yet disposed
// and we therefore still hold the FileShare.None exclusion.
// There may still be a race with another thread attempting a
// TryLockFile in parallel, but that is safely handled there.
File.Delete(FilePath);
}
finally
{
Stream.Dispose();
Stream = null;
}
}
public bool TryLock(int timeoutMs)
{
if (IsDisposed)
throw new ObjectDisposedException("Mutex");
if (Stream is not null)
throw new InvalidOperationException("Lock already held");
var sw = Stopwatch.StartNew();
do
{
try
{
// Attempt to acquire lock while holding guard.
using var guard = LockGuard();
if (TryLockFile())
return true;
}
catch (Exception)
{
return false;
}
// See comment in LockGuard.
Thread.Sleep(1);
} while (sw.ElapsedMilliseconds < timeoutMs);
return false;
}
public bool CouldLock()
{
if (IsDisposed)
return false;
if (Stream is not null)
return false;
try
{
// Attempt to acquire lock while holding guard, and if successful
// immediately unlock again while still holding guard. This ensures
// no other thread will spuriously observe the lock as held due to
// the lock attempt here.
using var guard = LockGuard();
if (TryLockFile())
{
UnlockFile();
return true;
}
}
catch (Exception)
{
return false;
}
return false;
}
public void Dispose()
{
if (IsDisposed)
return;
IsDisposed = true;
if (Stream is not null)
{
try
{
UnlockFile();
}
catch (Exception)
{
}
}
}
}
internal sealed class ServerNamedMutex : IServerMutex
{
public readonly Mutex Mutex;
public bool IsDisposed { get; private set; }
public bool IsLocked { get; private set; }
public ServerNamedMutex(string mutexName, out bool createdNew)
{
Mutex = new Mutex(
initiallyOwned: true,
name: mutexName,
createdNew: out createdNew
);
if (createdNew)
IsLocked = true;
}
public static bool WasOpen(string mutexName)
{
Mutex? m = null;
try
{
return Mutex.TryOpenExisting(mutexName, out m);
}
catch
{
// In the case an exception occurred trying to open the Mutex then
// the assumption is that it's not open.
return false;
}
finally
{
m?.Dispose();
}
}
public bool TryLock(int timeoutMs)
{
if (IsDisposed)
throw new ObjectDisposedException("Mutex");
if (IsLocked)
throw new InvalidOperationException("Lock already held");
return IsLocked = Mutex.WaitOne(timeoutMs);
}
public void Dispose()
{
if (IsDisposed)
return;
IsDisposed = true;
try
{
if (IsLocked)
Mutex.ReleaseMutex();
}
finally
{
Mutex.Dispose();
IsLocked = false;
}
}
}
}
|