Queues a user-mode Asynchronous Procedure Call (APC) on the specified thread.

Parameters

• ThreadHandle - a handle the the thread granting the THREAD_SET_CONTEXT access.
• ReserveHandle - an optional handle to the reserve object (see NtAllocateReserveObject) to avoid memory allocations.
• ApcFlags - the flags that control properties of the APC.
• ApcRoutine - the address of the function to invoke.
• ApcArgument1 - the first argument to pass to the APC routine.
• ApcArgument2 - the second argument to pass to the APC routine.
• ApcArgument3 - the third argument to pass to the APC routine.

Supported flags

• QUEUE_USER_APC_FLAGS_NONE - indicates that none of the flags listed below are used. The behavior defaults to regular APCs that require the thread to first enter an alertable wait via NtDelayExecution (or a similar function) or call NtTestAlert.
• QUEUE_USER_APC_FLAGS_SPECIAL_USER_APC - queue a special user-mode APC that does not require the thread to enter an alertable state. The APC will be executed on the next thread's transition to user mode.
• QUEUE_USER_APC_CALLBACK_DATA_CONTEXT - let the callback routine receive the context (set of registers) that was interrupted when the thread was directed to call the APC function.

Remarks

To queue a WoW64 APC, encode the ApcRoutine parameter using the Wow64EncodeApcRoutine macro or use RtlQueueApcWow64Thread.

Note that user APCs on the Native API level have three parameters in contrast with the Win32 APCs that only have one.

Related Win32 API

• QueueUserAPC2

Required OS version

This function was introduced in Windows 11.

See also

• NtQueueApcThread
• NtQueueApcThreadEx
• RtlQueueApcWow64Thread
• NtOpenThread
• NtTestAlert