On Jul 16, 2007, at 12:48 PM, Paul Goyette wrote:
> Other than manipulating a process's signal mask (for example, using  
> signal(3)), what can prevent delivery of a signal?
>
> In particular, I've occassionally seen processes "hang" waiting for  
> something (I/O completion?), and typing Control/C doesn't work.   
> Once the Control/C signal doesn't work, not even a `kill -KILL` can  
> abort
> that process!  Yet, if instead of typing Control/C first you simply
> try `kill -KILL` then the target process is killed.
>
> Can someone explain what's going on?

Delivery of signals is done asyncronously during normal program  
execution; if the process has context-switched out to execute a  
system call and is running in the kernel instead, any additional  
signals will typically be held until the process returns, but see  
"man siginterrupt"....

-- 
-Chuck