On Thu, May 01, 2008 at 08:17:07AM -0500, Kumar Gala wrote:

On May 1, 2008, at 3:24 AM, Paul Mackerras wrote:

quoted

The most common cases are (a) something that ultimately generates
input on a tty (e.g. a character arriving on a serial port) and that
input turns out to be a ^C or similar, or (b) something that signals
I/O completion and the program doing the I/O has requested
notification by a SIGIO.  But in general any driver code can send a
signal to userspace if it wants.

And, of course, SIGALRM and similar timer mechanisms.

ok.  Was just wondering how the async exception know that the signal  
it wanted to send belonged to the particular process that is running.   
But I guess there are cases that the signal is really intended for who  
ever is currently running?

No, it knows based on its own data structures who it's intended for --
and sometimes that happens to be the currently running process.

-Scott