KeDelayExecutionThread function

The KeDelayExecutionThread routine puts the current thread into an alertable or nonalertable wait state for a specified interval.


NTSTATUS KeDelayExecutionThread(
  BOOLEAN         Alertable,



Specifies the processor mode in which the caller is waiting, which can be either KernelMode or UserMode. Lower-level drivers should specify KernelMode.


Specifies TRUE if the wait is alertable. Lower-level drivers should specify FALSE.


Specifies the absolute or relative time, in units of 100 nanoseconds, for which the wait is to occur. A negative value indicates relative time. Absolute expiration times track any changes in system time; relative expiration times are not affected by system time changes.

Return Value

KeDelayExecutionThread returns one of the following values that describes how the delay was completed:

Return code Description
The delay completed because the specified interval elapsed.
The delay completed because the thread was alerted.
A user-mode APC was delivered before the specified Interval expired.

Note that the NT_SUCCESS macro recognizes all of these status values as "success" values.


The expiration time is computed and the current thread is put in a wait state. When the specified interval has passed, the thread exits the wait state and is put in the ready state, becoming eligible for execution.

The Alertable parameter determines when the thread can be alerted and its wait state consequently aborted. For additional information, see Waits and APCs.

If the WaitMode parameter is UserMode, the kernel stack can be swapped out during the wait. Consequently, a caller must never attempt to pass parameters on the stack when calling KeDelayExecutionThread using the UserMode argument.

It is especially important to check the return value of KeDelayExecutionThread when the WaitMode parameter is UserMode or Alertable is TRUE, because KeDelayExecutionThread might return early with a status of STATUS_USER_APC or STATUS_ALERTED.

All long term waits that can be aborted by a user should be UserMode waits and Alertable should be set to FALSE.

Where possible, Alertable should be set to FALSE and WaitMode should be set to KernelMode, in order to reduce driver complexity. The principal exception to this guideline is when the wait is a long-term wait.

The expiration time of the delay is expressed as either an absolute time at which the delay is to expire, or a time relative to the current system time. If the Interval parameter value is positive, the expiration time is an absolute time. If this value is negative, the expiration time is a relative time.

Expiration times are measured relative to the system clock, and the accuracy with which the operating system can detect when a timer expires is limited by the granularity of the system clock. For more information, see Timer Accuracy.


Minimum supported client Available starting with Windows 2000.
Target Platform Universal
Header wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe
DDI compliance rules IrqlKeApcLte1, PowerIrpDDis, HwStorPortProhibitedDDIs

See Also