_VWIN32_QueueUserApc

Queues a call to the specified ring 3 code in the specified thread and returns. The thread must have been placed in an alertable wait state by using one of the following Win32 functions: SleepEx, WaitForMultipleObjectsEx, or WaitForSingleObjectEx. (To make an alertable wait state, set the fAlertable parameter in these Win32 functions to TRUE.) This service may be called at event time, but not at interrupt time. Uses EAX, ECX, EDX, and Flags.

• Returns a non-zero value in EAX and clears the zero flag if successful in queuing the asynchronous procedure call (APC). If unable to allocate memory for the APC, EAX contains 0 and the zero flag is set.

pfnRing3APC

Flat offset of ring 3 asynchronous procedure. If 0, the thread is only awakened.

dwParam

DWORD parameter to pass to APC.

ptcb

Ring 0 thread handle. If -1, use kernel service thread.