which signal will caused "wait_event_interruptible" interrupted?

There are wait_event_interruptible in a driver to wait until message is aviliable.But this function was interrupted by a signal. I find out this in manpage: > The function will return -ERESTARTSYS if it was interrupted by a signal Another community tell me the signal is "nonblocked pending signals". So I want to know what is "nonblocked pending signals"? And how to find out whitch thread produce this signal? Could I produce this signal manuly to interrupt "wait_event_interruptible " ?