SuspendThread function (processthreadsapi.h)

Suspends the specified thread.

A 64-bit application can suspend a WOW64 thread using the Wow64SuspendThread function.


DWORD SuspendThread(
  [in] HANDLE hThread


[in] hThread

A handle to the thread that is to be suspended.

The handle must have the THREAD_SUSPEND_RESUME access right. For more information, see Thread Security and Access Rights.

Return value

If the function succeeds, the return value is the thread's previous suspend count; otherwise, it is (DWORD) -1. To get extended error information, use the GetLastError function.


If the function succeeds, execution of the specified thread is suspended and the thread's suspend count is incremented. Suspending a thread causes the thread to stop executing user-mode (application) code.

This function is primarily designed for use by debuggers. It is not intended to be used for thread synchronization. Calling SuspendThread on a thread that owns a synchronization object, such as a mutex or critical section, can lead to a deadlock if the calling thread tries to obtain a synchronization object owned by a suspended thread. To avoid this situation, a thread within an application that is not a debugger should signal the other thread to suspend itself. The target thread must be designed to watch for this signal and respond appropriately.

Each thread has a suspend count (with a maximum value of MAXIMUM_SUSPEND_COUNT). If the suspend count is greater than zero, the thread is suspended; otherwise, the thread is not suspended and is eligible for execution. Calling SuspendThread causes the target thread's suspend count to be incremented. Attempting to increment past the maximum suspend count causes an error without incrementing the count.

The ResumeThread function decrements the suspend count of a suspended thread.

Windows Phone 8.1: This function is supported for Windows Phone Store apps on Windows Phone 8.1 and later.

Windows 8.1 and Windows Server 2012 R2: This function is supported for Windows Store apps on Windows 8.1, Windows Server 2012 R2, and later.


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 Vista, Windows 7, Windows Server 2008 Windows Server 2008 R2)
Library Kernel32.lib; WindowsPhoneCore.lib on Windows Phone 8.1
DLL Kernel32.dll; KernelBase.dll on Windows Phone 8.1

See also


Process and Thread Functions


Suspending Thread Execution