SpinLock SpinLock SpinLock SpinLock Struct

Definizione

Fornisce un primitiva di blocco a esclusione reciproca in cui un thread che tenta di acquisire il blocco attende in un ciclo eseguendo controlli ripetuti finché il blocco non diventa disponibile.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
Ereditarietà
Attributi

Esempi

Nell'esempio seguente viene illustrato come utilizzare 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

Commenti

Per un esempio di come usare uno spinlock, vedere come: Usare SpinLock per la sincronizzazione di basso livello.For an example of how to use a Spin Lock, see How to: Use SpinLock for Low-Level Synchronization.

SpinLock è utilizzabile per i blocchi a livello foglia in cui l'allocazione dell'oggetto di cui è inclusa con una Monitor, dimensioni o a causa di un utilizzo elevato di garbage collection, è eccessivamente costoso.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. Può essere utile per evitare il blocco; uno spinlock Tuttavia, se si prevede una quantità significativa di blocco, è probabilmente non deve usare spinlock a causa della rotazione eccessiva.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. Rotazione con stato può essere utile quando i blocchi sono grandi in numero (ad esempio, un blocco per ogni nodo in un elenco collegato) e con granularità fine e anche quando i tempi di mantenimento del blocco sono sempre molto brevi.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. In generale, mentre vengono premuti uno spinlock, uno necessario evitare qualsiasi di queste azioni:In general, while holding a spin lock, one should avoid any of these actions:

  • il blocco,blocking,

  • la chiamata a qualsiasi elemento che a sua volta può bloccare,calling anything that itself may block,

  • blocco viene mantenuto attivo più di una selezione in una sola volta,holding more than one spin lock at once,

  • effettuando chiamate (interfaccia e metodi virtuali), inviate dinamicamentemaking dynamically dispatched calls (interface and virtuals),

  • effettuando in modo statico inviate chiamate a qualsiasi codice che non si possiede, omaking statically dispatched calls into any code one doesn't own, or

  • allocazione di memoria.allocating memory.

SpinLock deve essere utilizzato solo dopo aver determinato che questo modo migliorano le prestazioni di un'applicazione.SpinLock should only be used after you have been determined that doing so will improve an application's performance. È anche importante notare che SpinLock è un tipo di valore, per motivi di prestazioni.It is also important to note that SpinLock is a value type, for performance reasons. Per questo motivo, è necessario prestare attenzione a non copiare accidentalmente un SpinLock istanze, come le due istanze (originale e la copia) sarebbe completamente indipendenti una da altra, che probabilmente potrebbe causare un comportamento errato dell'applicazione.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. Se un SpinLock istanza debba essere passata, deve essere passato per riferimento e non per valore.If a SpinLock instance must be passed around, it should be passed by reference rather than by value.

Non archiviare SpinLock istanze in campi di sola lettura.Do not store SpinLock instances in readonly fields.

Costruttori

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

Inizializza una nuova istanza della struttura SpinLock con l'opzione di rilevamento degli ID dei thread per migliorare il debug.Initializes a new instance of the SpinLock structure with the option to track thread IDs to improve debugging.

Proprietà

IsHeld IsHeld IsHeld IsHeld

Ottiene un valore che indica se attualmente il blocco è mantenuto da un thread.Gets whether the lock is currently held by any thread.

IsHeldByCurrentThread IsHeldByCurrentThread IsHeldByCurrentThread IsHeldByCurrentThread

Ottiene un valore che indica se il blocco è mantenuto dal thread corrente.Gets whether the lock is held by the current thread.

IsThreadOwnerTrackingEnabled IsThreadOwnerTrackingEnabled IsThreadOwnerTrackingEnabled IsThreadOwnerTrackingEnabled

Ottiene un valore che indica se per questa istanza è abilitato il rilevamento della proprietà dei thread.Gets whether thread ownership tracking is enabled for this instance.

Metodi

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

Acquisisce il blocco in modo affidabile, in modo tale che anche se si verifica un'eccezione all'interno della chiamata al metodo, è possibile esaminare l'oggetto lockTaken in maniera affidabile per determinare se il blocco è stato acquisito.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()

Rilascia il blocco.Releases the lock.

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

Rilascia il blocco.Releases the lock.

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

Tenta di acquisire il blocco in modo affidabile, in modo tale che anche se si verifica un'eccezione all'interno della chiamata al metodo, è possibile esaminare l'oggetto lockTaken in maniera affidabile per determinare se il blocco è stato acquisito.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)

Tenta di acquisire il blocco in modo affidabile, in modo tale che anche se si verifica un'eccezione all'interno della chiamata al metodo, è possibile esaminare l'oggetto lockTaken in maniera affidabile per determinare se il blocco è stato acquisito.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)

Tenta di acquisire il blocco in modo affidabile, in modo tale che anche se si verifica un'eccezione all'interno della chiamata al metodo, è possibile esaminare l'oggetto lockTaken in maniera affidabile per determinare se il blocco è stato acquisito.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.

Si applica a

Thread safety

Tutti i membri di SpinLock sono thread-safe e possono essere utilizzati da più thread contemporaneamente.All members of SpinLock are thread-safe and may be used from multiple threads concurrently.

Vedi anche