Interrupt Handler in C - HOW??

[David Dymm]

I would like to write an interrupt handling mechanism
in 'C' to work in the following way:

1) Set up the signal facility:

	signal (SIGALRM, alarm_handler)

2) Set the alarm:

	ualarm (100000, 0)  <== This will send a signal after
				100,0000 microseconds.

3) The interrupt handler "alarm_handler" is called with
    the signal mechanism when the alarm timer times out.
    Let's call "location A" the place where we were in
    the code when we were interrupted by the timer.

    When "alarm_handler" has finished its local processing,
    I do NOT want to return control back to where the
    interrupt occurred!!!!
    Instead, I want to "longjmp" to another function in the
    program.  When that function has  completed its work,
    I want to return to "location A".


The question is:  How do I return to "location A" ???

I have looked at the "sigstack" mechanism, and also at
the definitions for "sigcontext" and "sigstack" in "signal.h".
But I do not see how to put this all together to accomplish
my task.  The system saves the state of the process on the
signal stack when "signal" causes control to jump to 
"alarm_handler".  How do I get at that information AND more
importantly, how do I use that information to accomplish
my task.

Any ideas???


David Dymm			Software Engineer

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