SpinLock Struktur
Definition
Wichtig
Einige Informationen beziehen sich auf Vorabversionen, die vor dem Release ggf. grundlegend überarbeitet werden. Microsoft übernimmt hinsichtlich der hier bereitgestellten Informationen keine Gewährleistungen, seien sie ausdrücklich oder konkludent.
Stellt einen Mutex-Sperrprimitiven bereit, wobei ein Thread, der versucht, die Sperre abzurufen, in einer Schleife wartet, die laufend prüft, ob die Sperre verfügbar wird.
public value class SpinLockpublic struct SpinLock[System.Runtime.InteropServices.ComVisible(false)]
public struct SpinLocktype SpinLock = struct[<System.Runtime.InteropServices.ComVisible(false)>]
type SpinLock = structPublic Structure SpinLock- Vererbung
- Attribute
Beispiele
Im folgenden Beispiel wird gezeigt, wie Sie eine 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
Hinweise
Ein Beispiel für die Verwendung einer Spin-Sperre finden Sie unter How to: Use SpinLock for Low-Level Sync.
Spinsperren können für Blattebenensperren verwendet werden, bei denen die Objektzuweisung durch verwendung einer Monitor, in Größe oder aufgrund des Müllsammlungsdrucks implizite Objektzuordnung übermäßig teuer ist. Eine Spin-Sperre kann nützlich sein, um das Blockieren zu vermeiden; Wenn Sie jedoch eine erhebliche Menge an Blockierung erwarten, sollten Sie wahrscheinlich keine Drehsperren aufgrund übermäßiger Drehung verwenden. Das Drehen kann nützlich sein, wenn Sperrungen fein korniert und groß sind (z. B. eine Sperre pro Knoten in einer verknüpften Liste) und auch wenn die Sperrzeit immer extrem kurz ist. Im Allgemeinen sollte beim Halten einer Spin-Sperre eine der folgenden Aktionen vermieden werden:
Blockieren
Aufrufen von Elementen, die sich selbst blockieren können,
Gleichzeitiges Halten von mehr als einer Spin-Sperre
Dynamisches Senden von Anrufen (Schnittstelle und Virtuelle),
Ausführen von statisch verteilten Aufrufen in einen Code, der nicht gehört oder
Zuordnen des Arbeitsspeichers.
SpinLock sollte nur verwendet werden, nachdem Sie festgestellt haben, dass dies die Leistung einer Anwendung verbessert. Es ist auch wichtig zu beachten, dass SpinLock es sich um einen Werttyp handelt, aus Leistungsgründen. Aus diesem Grund müssen Sie sehr vorsichtig sein, eine Instanz versehentlich zu kopieren SpinLock , da die beiden Instanzen (das Original und die Kopie) dann vollständig unabhängig voneinander sein würden, was wahrscheinlich zu fehlerhaftem Verhalten der Anwendung führt. Wenn eine SpinLock Instanz umgeleitet werden muss, sollte sie durch Verweis übergeben werden, anstatt nach Wert.
Speichern SpinLock Sie keine Instanzen in Readonly-Feldern.
Konstruktoren
| SpinLock(Boolean) |
Initialisiert eine neue Instanz der SpinLock-Struktur mit der Option, Thread-IDs nachzuverfolgen, um das Debuggen zu vereinfachen. |
Eigenschaften
| IsHeld |
Ruft einen Wert ab, der angibt, ob die Sperre zurzeit von einem Thread verwendet wird. |
| IsHeldByCurrentThread |
Ruft einen Wert ab, der angibt, ob die Sperre vom aktuellen Thread verwendet wird. |
| IsThreadOwnerTrackingEnabled |
Ruft einen Wert ab, der angibt, ob die Threadbesitznachverfolgung für diese Instanz aktiviert ist. |
Methoden
| Enter(Boolean) |
Ruft die Sperre zuverlässig ab, sodass |
| Exit() |
Hebt die Sperre auf. |
| Exit(Boolean) |
Hebt die Sperre auf. |
| TryEnter(Boolean) |
Versucht, die Sperre zuverlässig abzurufen, sodass |
| TryEnter(Int32, Boolean) |
Versucht, die Sperre zuverlässig abzurufen, sodass |
| TryEnter(TimeSpan, Boolean) |
Versucht, die Sperre zuverlässig abzurufen, sodass |
Gilt für
Threadsicherheit
Alle Elemente sind SpinLock threadsicher und können gleichzeitig von mehreren Threads verwendet werden.