Article
11/18/2011

Thread.SpinWait Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Causes a thread to wait the number of times defined by the iterations parameter.

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

Syntax

'Declaration
<SecuritySafeCriticalAttribute> _
Public Shared Sub SpinWait ( _
    iterations As Integer _
)

[SecuritySafeCriticalAttribute]
public static void SpinWait(
    int iterations
)

Parameters

iterations
Type: System.Int32
A 32-bit signed integer that defines how long a thread should wait.

Remarks

The SpinWait method is useful for implementing locks. Classes in the .NET Framework, such as Monitor, use this method internally. SpinWait essentially puts the processor into a very tight loop, with the loop count specified by the iterations parameter. The duration of the wait therefore depends on the speed of the processor.

Contrast this with the Sleep method. A thread that calls Sleep yields the rest of its current slice of processor time, even if the specified interval is zero. Specifying a non-zero interval for Sleep removes the thread from consideration by the thread scheduler until the time interval has elapsed.

SpinWait is not generally useful for ordinary applications. In most cases, you should use the synchronization classes provided by the .NET Framework; for example, call Monitor.Enter or a statement that wraps Monitor.Enter (lock in C# or SyncLock in Visual Basic).

Caution:
In the rare case where it is advantageous to avoid a context switch, such as when you know that a state change is imminent, make a call to the SpinWait method in your loop. The code that SpinWait executes is designed to prevent problems that can occur on computers with multiple processors. For example, on computers with multiple Intel processors employing Hyper-Threading technology, SpinWait prevents processor starvation in certain situations.

In the rare case where it is advantageous to avoid a context switch, such as when you know that a state change is imminent, make a call to the SpinWait method in your loop. The code that SpinWait executes is designed to prevent problems that can occur on computers with multiple processors. For example, on computers with multiple Intel processors employing Hyper-Threading technology, SpinWait prevents processor starvation in certain situations.

Version Notes

Silverlight for Windows Phone

When a user navigates away from a Windows Phone application, the application is typically put into a dormant state. When the user returns to a dormant application, the application automatically resumes. If the application is put into a dormant state while this API is being used, the API will not complete as expected. Applications should be designed to handle this possibility. For more information about the Windows Phone execution model, see Execution Model for Windows Phone.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.