SetThreadpoolTimer function (threadpoolapiset.h)

Sets the timer object, replacing the previous timer, if any. A worker thread calls the timer object's callback after the specified timeout expires.


void SetThreadpoolTimer(
  [in, out]      PTP_TIMER pti,
  [in, optional] PFILETIME pftDueTime,
  [in]           DWORD     msPeriod,
  [in]           DWORD     msWindowLength


[in, out] pti

A pointer to a TP_TIMER structure that defines the timer object to set. The CreateThreadpoolTimer function returns this pointer.

[in, optional] pftDueTime

A pointer to a FILETIME structure that specifies the absolute or relative time at which the timer should expire. If positive or zero, it indicates the absolute time since January 1, 1601 (UTC), measured in 100 nanosecond units. If negative, it indicates the amount of time to wait relative to the current time. For more information about time values, see File Times.

If this parameter is NULL, the timer object will cease to queue new callbacks (but callbacks already queued will still occur).

The timer is set if the pftDueTime parameter is non-NULL.

[in] msPeriod

The timer period, in milliseconds. If this parameter is zero, the timer is signaled once. If this parameter is greater than zero, the timer is periodic. A periodic timer automatically reactivates each time the period elapses, until the timer is canceled.

[in] msWindowLength

The maximum amount of time the system can delay before calling the timer callback. If this parameter is not set to zero, the system can batch calls to conserve power.

Return value



Setting the timer cancels the previous timer, if any.

In some cases, callback functions might run after an application closes the threadpool timer. To prevent this behavior, an application should follow the steps described in CloseThreadpoolTimer.

If the due time specified by pftDueTime is relative, the time that the system spends in sleep or hibernation does not count toward the expiration of the timer. The timer is signaled when the cumulative amount of elapsed time the system spends in the waking state equals the timer's relative due time or period. If the due time specified by pftDueTime is absolute, the time that the system spends in sleep or hibernation does count toward the expiration of the timer. If the timer expires while the system is sleeping, the timer is signaled immediately when the system wakes.

If the due time specified by pftDueTime is zero, then the timer expires immediately.

To compile an application that uses this function, define _WIN32_WINNT as 0x0600 or higher.


For an example, see Using the Thread Pool Functions.


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

See also




Thread Pools