Hi, 
several applications/drivers running under qnx need to get kernel privilege. Therefore i used ThreadCtl(_NTO_TCTL_IO, 
NULL) in different processes/threads.
Now I noticed that one of processes is blocked about 20 seconds when calling this function. According to API doc, 
ThreadCtl is a non-blocking call, therefore 20 seconds delay/blocking shouldn't happen. 
On some internet forum, it seems that ThreadCtl needs to lock process memory pages first in order to avoid page fault. 
Is that the reason that ThreadCtl(...) blocking my process execution?