SpinLock SpinLock SpinLock SpinLock Struct

Définition

Fournit une primitive de verrou d'exclusion mutuelle où un thread qui tente d'acquérir le verrou attend dans une boucle en vérifiant de manière répétée jusqu'à ce que le verrou devienne disponible.Provides a mutual exclusion lock primitive where a thread trying to acquire the lock waits in a loop repeatedly checking until the lock becomes available.

public value class SpinLock
[System.Runtime.InteropServices.ComVisible(false)]
public struct SpinLock
type SpinLock = struct
Public Structure SpinLock
Héritage
Attributs

Exemples

L’exemple suivant montre comment utiliser un SpinLock:The following example shows how to use a SpinLock:

using System;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;


class SpinLockDemo
{


    // Demonstrates:
    //      Default SpinLock construction ()
    //      SpinLock.Enter(ref bool)
    //      SpinLock.Exit()
    static void SpinLockSample1()
    {
        SpinLock sl = new SpinLock();

        StringBuilder sb = new StringBuilder();

        // Action taken by each parallel job.
        // Append to the StringBuilder 10000 times, protecting
        // access to sb with a SpinLock.
        Action action = () =>
        {
            bool gotLock = false;
            for (int i = 0; i < 10000; i++)
            {
                gotLock = false;
                try
                {
                    sl.Enter(ref gotLock);
                    sb.Append((i % 10).ToString());
                }
                finally
                {
                    // Only give up the lock if you actually acquired it
                    if (gotLock) sl.Exit();
                }
            }
        };

        // Invoke 3 concurrent instances of the action above
        Parallel.Invoke(action, action, action);

        // Check/Show the results
        Console.WriteLine("sb.Length = {0} (should be 30000)", sb.Length);
        Console.WriteLine("number of occurrences of '5' in sb: {0} (should be 3000)",
            sb.ToString().Where(c => (c == '5')).Count());
    }

    // Demonstrates:
    //      Default SpinLock constructor (tracking thread owner)
    //      SpinLock.Enter(ref bool)
    //      SpinLock.Exit() throwing exception
    //      SpinLock.IsHeld
    //      SpinLock.IsHeldByCurrentThread
    //      SpinLock.IsThreadOwnerTrackingEnabled
    static void SpinLockSample2()
    {
        // Instantiate a SpinLock
        SpinLock sl = new SpinLock();

        // These MRESs help to sequence the two jobs below
        ManualResetEventSlim mre1 = new ManualResetEventSlim(false);
        ManualResetEventSlim mre2 = new ManualResetEventSlim(false);
        bool lockTaken = false;

        Task taskA = Task.Factory.StartNew(() =>
        {
            try
            {
                sl.Enter(ref lockTaken);
                Console.WriteLine("Task A: entered SpinLock");
                mre1.Set(); // Signal Task B to commence with its logic

                // Wait for Task B to complete its logic
                // (Normally, you would not want to perform such a potentially
                // heavyweight operation while holding a SpinLock, but we do it
                // here to more effectively show off SpinLock properties in
                // taskB.)
                mre2.Wait();
            }
            finally
            {
                if (lockTaken) sl.Exit();
            }
        });

        Task taskB = Task.Factory.StartNew(() =>
        {
            mre1.Wait(); // wait for Task A to signal me
            Console.WriteLine("Task B: sl.IsHeld = {0} (should be true)", sl.IsHeld);
            Console.WriteLine("Task B: sl.IsHeldByCurrentThread = {0} (should be false)", sl.IsHeldByCurrentThread);
            Console.WriteLine("Task B: sl.IsThreadOwnerTrackingEnabled = {0} (should be true)", sl.IsThreadOwnerTrackingEnabled);

            try
            {
                sl.Exit();
                Console.WriteLine("Task B: Released sl, should not have been able to!");
            }
            catch (Exception e)
            {
                Console.WriteLine("Task B: sl.Exit resulted in exception, as expected: {0}", e.Message);
            }

            mre2.Set(); // Signal Task A to exit the SpinLock
        });

        // Wait for task completion and clean up
        Task.WaitAll(taskA, taskB);
        mre1.Dispose();
        mre2.Dispose();
    }

    // Demonstrates:
    //      SpinLock constructor(false) -- thread ownership not tracked
    static void SpinLockSample3()
    {
        // Create SpinLock that does not track ownership/threadIDs
        SpinLock sl = new SpinLock(false);

        // Used to synchronize with the Task below
        ManualResetEventSlim mres = new ManualResetEventSlim(false);

        // We will verify that the Task below runs on a separate thread
        Console.WriteLine("main thread id = {0}", Thread.CurrentThread.ManagedThreadId);

        // Now enter the SpinLock.  Ordinarily, you would not want to spend so
        // much time holding a SpinLock, but we do it here for the purpose of 
        // demonstrating that a non-ownership-tracking SpinLock can be exited 
        // by a different thread than that which was used to enter it.
        bool lockTaken = false;
        sl.Enter(ref lockTaken);

        // Create a separate Task from which to Exit() the SpinLock
        Task worker = Task.Factory.StartNew(() =>
        {
            Console.WriteLine("worker task thread id = {0} (should be different than main thread id)",
                Thread.CurrentThread.ManagedThreadId);

            // Now exit the SpinLock
            try
            {
                sl.Exit();
                Console.WriteLine("worker task: successfully exited SpinLock, as expected");
            }
            catch (Exception e)
            {
                Console.WriteLine("worker task: unexpected failure in exiting SpinLock: {0}", e.Message);
            }

            // Notify main thread to continue
            mres.Set();
        });

        // Do this instead of worker.Wait(), because worker.Wait() could inline the worker Task,
        // causing it to be run on the same thread.  The purpose of this example is to show that
        // a different thread can exit the SpinLock created (without thread tracking) on your thread.
        mres.Wait();

        // now Wait() on worker and clean up
        worker.Wait();
        mres.Dispose();
    }

}
Imports System.Text
Imports System.Threading
Imports System.Threading.Tasks


Module SpinLockDemo

    ' Demonstrates:
    ' Default SpinLock construction ()
    ' SpinLock.Enter(ref bool)
    ' SpinLock.Exit()
    Private Sub SpinLockSample1()
        Dim sl As New SpinLock()

        Dim sb As New StringBuilder()

        ' Action taken by each parallel job.
        ' Append to the StringBuilder 10000 times, protecting
        ' access to sb with a SpinLock.
        Dim action As Action =
            Sub()
                Dim gotLock As Boolean = False
                For i As Integer = 0 To 9999
                    gotLock = False
                    Try
                        sl.Enter(gotLock)
                        sb.Append((i Mod 10).ToString())
                    Finally
                        ' Only give up the lock if you actually acquired it
                        If gotLock Then
                            sl.[Exit]()
                        End If
                    End Try
                Next
            End Sub

        ' Invoke 3 concurrent instances of the action above
        Parallel.Invoke(action, action, action)

        ' Check/Show the results
        Console.WriteLine("sb.Length = {0} (should be 30000)", sb.Length)
        Console.WriteLine("number of occurrences of '5' in sb: {0} (should be 3000)", sb.ToString().Where(Function(c) (c = "5"c)).Count())
    End Sub

    ' Demonstrates:
    ' Default SpinLock constructor (tracking thread owner)
    ' SpinLock.Enter(ref bool)
    ' SpinLock.Exit() throwing exception
    ' SpinLock.IsHeld
    ' SpinLock.IsHeldByCurrentThread
    ' SpinLock.IsThreadOwnerTrackingEnabled
    Private Sub SpinLockSample2()
        ' Instantiate a SpinLock
        Dim sl As New SpinLock()

        ' These MRESs help to sequence the two jobs below
        Dim mre1 As New ManualResetEventSlim(False)
        Dim mre2 As New ManualResetEventSlim(False)
        Dim lockTaken As Boolean = False

        Dim taskA As Task = Task.Factory.StartNew(
            Sub()
                Try
                    sl.Enter(lockTaken)
                    Console.WriteLine("Task A: entered SpinLock")
                    mre1.[Set]()
                    ' Signal Task B to commence with its logic
                    ' Wait for Task B to complete its logic
                    ' (Normally, you would not want to perform such a potentially
                    ' heavyweight operation while holding a SpinLock, but we do it
                    ' here to more effectively show off SpinLock properties in
                    ' taskB.)
                    mre2.Wait()
                Finally
                    If lockTaken Then
                        sl.[Exit]()
                    End If
                End Try
            End Sub)

        Dim taskB As Task = Task.Factory.StartNew(
            Sub()
                mre1.Wait()
                ' wait for Task A to signal me
                Console.WriteLine("Task B: sl.IsHeld = {0} (should be true)", sl.IsHeld)
                Console.WriteLine("Task B: sl.IsHeldByCurrentThread = {0} (should be false)", sl.IsHeldByCurrentThread)
                Console.WriteLine("Task B: sl.IsThreadOwnerTrackingEnabled = {0} (should be true)", sl.IsThreadOwnerTrackingEnabled)

                Try
                    sl.[Exit]()
                    Console.WriteLine("Task B: Released sl, should not have been able to!")
                Catch e As Exception
                    Console.WriteLine("Task B: sl.Exit resulted in exception, as expected: {0}", e.Message)
                End Try

                ' Signal Task A to exit the SpinLock
                mre2.[Set]()
            End Sub)

        ' Wait for task completion and clean up
        Task.WaitAll(taskA, taskB)
        mre1.Dispose()
        mre2.Dispose()
    End Sub

    ' Demonstrates:
    ' SpinLock constructor(false) -- thread ownership not tracked
    Private Sub SpinLockSample3()
        ' Create SpinLock that does not track ownership/threadIDs
        Dim sl As New SpinLock(False)

        ' Used to synchronize with the Task below
        Dim mres As New ManualResetEventSlim(False)

        ' We will verify that the Task below runs on a separate thread
        Console.WriteLine("main thread id = {0}", Thread.CurrentThread.ManagedThreadId)

        ' Now enter the SpinLock.  Ordinarily, you would not want to spend so
        ' much time holding a SpinLock, but we do it here for the purpose of 
        ' demonstrating that a non-ownership-tracking SpinLock can be exited 
        ' by a different thread than that which was used to enter it.
        Dim lockTaken As Boolean = False
        sl.Enter(lockTaken)

        ' Create a separate Task
        Dim worker As Task = Task.Factory.StartNew(
            Sub()
                Console.WriteLine("worker task thread id = {0} (should be different than main thread id)", Thread.CurrentThread.ManagedThreadId)

                ' Now exit the SpinLock
                Try
                    sl.[Exit]()
                    Console.WriteLine("worker task: successfully exited SpinLock, as expected")
                Catch e As Exception
                    Console.WriteLine("worker task: unexpected failure in exiting SpinLock: {0}", e.Message)
                End Try

                ' Notify main thread to continue
                mres.[Set]()
            End Sub)

        ' Do this instead of worker.Wait(), because worker.Wait() could inline the worker Task,
        ' causing it to be run on the same thread. The purpose of this example is to show that
        ' a different thread can exit the SpinLock created (without thread tracking) on your thread.
        mres.Wait()

        ' now Wait() on worker and clean up
        worker.Wait()
        mres.Dispose()
    End Sub


End Module

Remarques

Pour obtenir un exemple montrant comment utiliser un verrou de rotation, consultez Comment : Utiliser le verrouillage SpinLock pour une synchronisation.For an example of how to use a Spin Lock, see How to: Use SpinLock for Low-Level Synchronization.

Verrous de rotation peuvent servir pour les verrous de niveau feuille où l’allocation d’objet implicite à l’aide un Monitor, taille, ou en raison de la pression du garbage collection, est trop coûteuse.Spin locks can be used for leaf-level locks where the object allocation implied by using a Monitor, in size or due to garbage collection pressure, is overly expensive. Un verrou de rotation peut être utile pour éviter les blocages ; Toutefois, si vous prévoyez une quantité importante de blocage, vous devez probablement pas utiliser les verrous de rotation en raison de la rotation excessive.A spin lock can be useful to avoid blocking; however, if you expect a significant amount of blocking, you should probably not use spin locks due to excessive spinning. Rotation peut s’avérer utile lorsque les verrous sont et affinés nombre (par exemple, un verrou par nœud dans une liste liée) et également lorsque les durées de blocage du verrou sont toujours très courtes.Spinning can be beneficial when locks are fine-grained and large in number (for example, a lock per node in a linked list) and also when lock hold-times are always extremely short. En règle générale, tout en maintenant un verrou de rotation, un doit éviter une de ces actions :In general, while holding a spin lock, one should avoid any of these actions:

  • blocage,blocking,

  • appel de tout élément pouvant lui-même se bloquer,calling anything that itself may block,

  • contenant à la fois de plus d’un verrou de rotationholding more than one spin lock at once,

  • passer dynamiquement des appels (interface et virtuels), distribuésmaking dynamically dispatched calls (interface and virtuals),

  • passer de manière statique des appels dans du code non possédé, distribués oumaking statically dispatched calls into any code one doesn't own, or

  • allocation de mémoire.allocating memory.

SpinLock doit être utilisé uniquement une fois que vous avez déterminé que cela améliorera les performances d’une application.SpinLock should only be used after you have been determined that doing so will improve an application's performance. Il est également important de noter que SpinLock est un type valeur, pour des raisons de performances.It is also important to note that SpinLock is a value type, for performance reasons. Pour cette raison, vous devez être très attention à ne pas copier par erreur une SpinLock de l’instance, comme les deux instances (d’origine et la copie) serait alors indépendamment les uns des autres, ce qui pourrait engendrer un comportement incorrect de l’application.For this reason, you must be very careful not to accidentally copy a SpinLock instance, as the two instances (the original and the copy) would then be completely independent of one another, which would likely lead to erroneous behavior of the application. Si un SpinLock instance doit être passée, il doit être passé par référence plutôt que par valeur.If a SpinLock instance must be passed around, it should be passed by reference rather than by value.

Ne stockez pas SpinLock instances dans les champs en lecture seule.Do not store SpinLock instances in readonly fields.

Constructeurs

SpinLock(Boolean) SpinLock(Boolean) SpinLock(Boolean) SpinLock(Boolean)

Initialise une nouvelle instance de la structure de SpinLock avec l'option permettant de suivre les ID de thread afin d'améliorer le débogage.Initializes a new instance of the SpinLock structure with the option to track thread IDs to improve debugging.

Propriétés

IsHeld IsHeld IsHeld IsHeld

Obtient une valeur qui indique si le verrou est actuellement détenu par un thread.Gets whether the lock is currently held by any thread.

IsHeldByCurrentThread IsHeldByCurrentThread IsHeldByCurrentThread IsHeldByCurrentThread

Obtient une valeur qui indique si le verrou est détenu par le thread actuel.Gets whether the lock is held by the current thread.

IsThreadOwnerTrackingEnabled IsThreadOwnerTrackingEnabled IsThreadOwnerTrackingEnabled IsThreadOwnerTrackingEnabled

Obtient une valeur qui indique si le suivi de la propriété des threads est activé pour cette instance.Gets whether thread ownership tracking is enabled for this instance.

Méthodes

Enter(Boolean) Enter(Boolean) Enter(Boolean) Enter(Boolean)

Acquiert le verrou de façon fiable, de sorte que même si une exception se produit dans l'appel de méthode, lockTaken peut être examiné de façon fiable pour déterminer si le verrou a été acquis.Acquires the lock in a reliable manner, such that even if an exception occurs within the method call, lockTaken can be examined reliably to determine whether the lock was acquired.

Exit() Exit() Exit() Exit()

Libère le verrou.Releases the lock.

Exit(Boolean) Exit(Boolean) Exit(Boolean) Exit(Boolean)

Libère le verrou.Releases the lock.

TryEnter(Boolean) TryEnter(Boolean) TryEnter(Boolean) TryEnter(Boolean)

Tente d'acquérir le verrou de façon fiable, de sorte que même si une exception se produit dans l'appel de méthode, lockTaken peut être examiné de façon fiable pour déterminer si le verrou a été acquis.Attempts to acquire the lock in a reliable manner, such that even if an exception occurs within the method call, lockTaken can be examined reliably to determine whether the lock was acquired.

TryEnter(Int32, Boolean) TryEnter(Int32, Boolean) TryEnter(Int32, Boolean) TryEnter(Int32, Boolean)

Tente d'acquérir le verrou de façon fiable, de sorte que même si une exception se produit dans l'appel de méthode, lockTaken peut être examiné de façon fiable pour déterminer si le verrou a été acquis.Attempts to acquire the lock in a reliable manner, such that even if an exception occurs within the method call, lockTaken can be examined reliably to determine whether the lock was acquired.

TryEnter(TimeSpan, Boolean) TryEnter(TimeSpan, Boolean) TryEnter(TimeSpan, Boolean) TryEnter(TimeSpan, Boolean)

Tente d'acquérir le verrou de façon fiable, de sorte que même si une exception se produit dans l'appel de méthode, lockTaken peut être examiné de façon fiable pour déterminer si le verrou a été acquis.Attempts to acquire the lock in a reliable manner, such that even if an exception occurs within the method call, lockTaken can be examined reliably to determine whether the lock was acquired.

S’applique à

Cohérence de thread

Tous les membres de SpinLock sont thread-safe et peuvent être utilisés à partir de plusieurs threads simultanément.All members of SpinLock are thread-safe and may be used from multiple threads concurrently.

Voir aussi