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AbandonedMutexException Class

The exception that is thrown when one thread acquires a Mutex object that another thread has abandoned by exiting without releasing it.

Namespace: System.Threading
Assembly: mscorlib (in mscorlib.dll)

[SerializableAttribute] 
[ComVisibleAttribute(false)] 
public class AbandonedMutexException : SystemException
/** @attribute SerializableAttribute() */ 
/** @attribute ComVisibleAttribute(false) */ 
public class AbandonedMutexException extends SystemException
SerializableAttribute 
ComVisibleAttribute(false) 
public class AbandonedMutexException extends SystemException
Not applicable.

When a thread abandons a mutex, the exception is thrown in the next thread that acquires the mutex. The thread might acquire the mutex because it was already waiting on the mutex or because it enters the mutex at a later time.

An abandoned mutex indicates a serious programming error. When a thread exits without releasing the mutex, the data structures protected by the mutex might not be in a consistent state. Prior to version 2.0 of the .NET Framework, such problems were hard to discover because no exception was thrown if a wait completed as the result of an abandoned mutex. For more information, see the Mutex class.

The next thread to request ownership of the mutex can handle this exception and proceed, provided that the integrity of the data structures can be verified.

The following code example executes a thread that abandons five mutexes, demonstrating their effects on the WaitOne, WaitAny, and WaitAll methods. The value of the MutexIndex property is displayed for the WaitAny call.

NoteNote:

The call to the WaitAny method is interrupted by one of the abandoned mutexes. The other abandoned mutex could still cause an AbandonedMutexException to be thrown by subsequent wait methods.


using System;
using System.Threading;

public class Example
{
    private static ManualResetEvent _dummy = new ManualResetEvent(false);

    private static Mutex _orphan1 = new Mutex();
    private static Mutex _orphan2 = new Mutex();
    private static Mutex _orphan3 = new Mutex();
    private static Mutex _orphan4 = new Mutex();
    private static Mutex _orphan5 = new Mutex();

    [MTAThread]
    public static void Main()
    {
        // Start a thread that takes all five mutexes, and then
        // ends without releasing them.
        //
        Thread t = new Thread(new ThreadStart(AbandonMutex));
        t.Start();
        // Make sure the thread is finished.
        t.Join();

        // Wait on one of the abandoned mutexes. The WaitOne returns
        // immediately, because its wait condition is satisfied by
        // the abandoned mutex, but on return it throws
        // AbandonedMutexException.
        try
        {
            _orphan1.WaitOne();
            Console.WriteLine("WaitOne succeeded.");
        }
        catch(AbandonedMutexException ex)
        {
            Console.WriteLine("Exception on return from WaitOne." +
                "\r\n\tMessage: {0}", ex.Message);
        }
        finally
        {
            // Whether or not the exception was thrown, the current
            // thread owns the mutex, and must release it.
            //
            _orphan1.ReleaseMutex();
        }

        // Create an array of wait handles, consisting of one
        // ManualResetEvent and two mutexes, using two more of the
        // abandoned mutexes.
        WaitHandle[] waitFor = {_dummy, _orphan2, _orphan3};

        // WaitAny returns when any of the wait handles in the 
        // array is signaled, so either of the two abandoned mutexes
        // satisfy its wait condition. On returning from the wait,
        // WaitAny throws AbandonedMutexException. The MutexIndex
        // property returns the lower of the two index values for 
        // the abandoned mutexes. Note that the Try block and the
        // Catch block obtain the index in different ways.
        //  
        try
        {
            int index = WaitHandle.WaitAny(waitFor);
            Console.WriteLine("WaitAny succeeded.");

            // The current thread owns the mutex, and must release
            // it.
            Mutex m = waitFor[index] as Mutex;
            if (m != null) m.ReleaseMutex();
        }
        catch(AbandonedMutexException ex)
        {
            Console.WriteLine("Exception on return from WaitAny at index {0}." +
                "\r\n\tMessage: {1}", ex.MutexIndex, ex.Message);

            // Whether or not the exception was thrown, the current
            // thread owns the mutex, and must release it.
            //
            if (ex.Mutex != null) ex.Mutex.ReleaseMutex();
        }

        // Use two more of the abandoned mutexes for the WaitAll call.
        // WaitAll doesn't return until all wait handles are signaled,
        // so the ManualResetEvent must be signaled by calling Set().
        _dummy.Set();
        waitFor[1] = _orphan4;
        waitFor[2] = _orphan5;

        // The signaled event and the two abandoned mutexes satisfy
        // the wait condition for WaitAll, but on return it throws
        // AbandonedMutexException. For WaitAll, the MutexIndex
        // property is always -1 and the Mutex property is always
        // null.
        //  
        try
        {
            WaitHandle.WaitAll(waitFor);
            Console.WriteLine("WaitAll succeeded.");
        }
        catch(AbandonedMutexException ex)
        {
            Console.WriteLine("Exception on return from WaitAll. MutexIndex = {0}." +
                "\r\n\tMessage: {1}", ex.MutexIndex, ex.Message);
        }
        finally
        {
            // Whether or not the exception was thrown, the current
            // thread owns the mutexes, and must release them.
            //
            _orphan4.ReleaseMutex();
            _orphan5.ReleaseMutex();
        }
    }

    [MTAThread]
    public static void AbandonMutex()
    {
        _orphan1.WaitOne();
        _orphan2.WaitOne();
        _orphan3.WaitOne();
        _orphan4.WaitOne();
        _orphan5.WaitOne();
        // Abandon the mutexes by exiting without releasing them.
        Console.WriteLine("Thread exits without releasing the mutexes.");
    }
}

/* This code example produces the following output:

Thread exits without releasing the mutexes.
Exception on return from WaitOne.
        Message: The wait completed due to an abandoned mutex.
Exception on return from WaitAny at index 1.
        Message: The wait completed due to an abandoned mutex.
Exception on return from WaitAll. MutexIndex = -1.
        Message: The wait completed due to an abandoned mutex.
 */

import System.*;
import System.Threading.*;

public class Example
{
    private static ManualResetEvent dummy = new ManualResetEvent(false);
    private static Mutex orphan1 = new Mutex();
    private static Mutex orphan2 = new Mutex();
    private static Mutex orphan3 = new Mutex();
    private static Mutex orphan4 = new Mutex();
    private static Mutex orphan5 = new Mutex();

    /** @attribute MTAThread()
     */
    public static void main(String[] args)
    {
        // Start a thread that takes all five mutexes, and then
        // ends without releasing them.
        //
        System.Threading.Thread t = new System.Threading.Thread(new 
            ThreadStart(AbandonMutex));
        t.Start();
        // Make sure the thread is finished.
        t.Join();

        // Wait on one of the abandoned mutexes. The WaitOne returns
        // immediately, because its wait condition is satisfied by
        // the abandoned mutex, but on return it throws
        // AbandonedMutexException.
        try {
            orphan1.WaitOne();
            Console.WriteLine("WaitOne succeeded.");
        }
        catch (AbandonedMutexException ex) {
            Console.WriteLine("Exception on return from WaitOne." +
                "\r\n\tMessage: {0}", ex.get_Message());
        }
        finally {
            // Whether or not the exception was thrown, the current
            // thread owns the mutex, and must release it.
            //
            orphan1.ReleaseMutex();
        }
        // Create an array of wait handles, consisting of one
        // ManualReset_Event and two mutexes, using two more of the
        // abandoned mutexes.
        WaitHandle waitFor[] =  { dummy, orphan2, orphan3 };

        // WaitAny returns when any of the wait handles in the 
        // array is signaled, so either of the two abandoned mutexes
        // satisfy its wait condition. On returning from the wait,
        // WaitAny throws AbandonedMutexException. The MutexIndex
        // property returns the lower of the two index values for 
        // the abandoned mutexes. Note that the Try block and the
        // Catch block obtain the index in different ways.
        //  
        try {
            int index = WaitHandle.WaitAny(waitFor);
            Console.WriteLine("WaitAny succeeded.");
            if (waitFor.get_Item(index) instanceof Mutex) {
                ((Mutex)(waitFor.get_Item(index))).ReleaseMutex();
            }
        }
        catch (AbandonedMutexException ex) {
            Console.WriteLine("Exception on return from WaitAny at index {0}" 
                + "\r\n\tMessage: {1}", (Int32)ex.get_MutexIndex(),
                ex.get_Message());

            // Whether or not the exception was thrown, the current
            // thread owns the mutex, and must release it.
            //
            if (ex.get_Mutex() != null) ex.get_Mutex().ReleaseMutex();
        }

        // Use two more of the abandoned mutexes for the WaitAll call.
        // WaitAll doesn't return until all wait handles are signaled,
        // so the ManualReset_Event must be signaled by calling set_().
        dummy.Set();
        waitFor.set_Item(1, orphan4);
        waitFor.set_Item(2, orphan5);

        // The signaled event and the two abandoned mutexes satisfy
        // the wait condition for WaitAll, but on return it throws
        // AbandonedMutexException. For WaitAll, the MutexIndex
        // property is always -1 and the Mutex property is always
        // null.
        //  
        try {
            WaitHandle.WaitAll(waitFor);
            Console.WriteLine("WaitAll succeeded.");
        }
        catch (AbandonedMutexException ex) {
            Console.WriteLine("Exception on return from WaitAny at index {0}" 
                + "\r\n\tMessage: {1}", (Int32)ex.get_MutexIndex(),
                ex.get_Message());
        }
        finally {
            // Whether or not the exception was thrown, the current
            // thread owns the mutexes, and must release them.
            //
            orphan4.ReleaseMutex();
            orphan5.ReleaseMutex();
        }
    } //main

    /** @attribute MTAThread()
     */
    public static void AbandonMutex()
    {
        orphan1.WaitOne();
        orphan2.WaitOne();
        orphan3.WaitOne();
        orphan4.WaitOne();
        orphan5.WaitOne();
        // Abandon the mutexes by exiting without releasing them.
        Console.WriteLine("Thread exits without releasing the mutexes.");
    } //AbandonMutex
} //Example

/* This code example produces the following output:

Thread exits without releasing the mutexes.
Exception on return from WaitOne.
        Message: The wait completed due to an abandoned mutex.
Exception on return from WaitAny at index 1.
        Message: The wait completed due to an abandoned mutex.
Exception on return from WaitAll. MutexIndex = -1.
        Message: The wait completed due to an abandoned mutex.
 */

System.Object
   System.Exception
     System.SystemException
      System.Threading.AbandonedMutexException

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

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