SwitchToThread function (processthreadsapi.h)

Causes the calling thread to yield execution to another thread that is ready to run on the current processor. The operating system selects the next thread to be executed.


BOOL SwitchToThread();

Return value

If calling the SwitchToThread function caused the operating system to switch execution to another thread, the return value is nonzero.

If there are no other threads ready to execute, the operating system does not switch execution to another thread, and the return value is zero.


The yield of execution is in effect for up to one thread-scheduling time slice on the processor of the calling thread. The operating system will not switch execution to another processor, even if that processor is idle or is running a thread of lower priority.

After the yielding thread's time slice elapses, the operating system reschedules execution for the yielding thread. The rescheduling is determined by the priority of the yielding thread and the status of other threads that are available to run.

Note that the operating system will not switch to a thread that is being prevented from running only by concurrency control. For example, an I/O completion port or thread pool limits the number of associated threads that can run. If the maximum number of threads is already running, no additional associated thread can run until a running thread finishes. If a thread uses SwitchToThread to wait for one of the additional associated threads to accomplish some work, the process might deadlock.

To compile an application that uses this function, define _WIN32_WINNT as 0x0400 or later. For more information, see Using the Windows Headers.


Requirement Value
Minimum supported client Windows XP [desktop apps | UWP apps]
Minimum supported server Windows Server 2003 [desktop apps | UWP apps]
Target Platform Windows
Header processthreadsapi.h (include Windows.h on Windows Server 2003, Windows Vista, Windows 7, Windows Server 2008 Windows Server 2008 R2)
Library Kernel32.lib
DLL Kernel32.dll

See also

Process and Thread Functions


Suspending Thread Execution