A notion for consideration.

[Chris Moller <cmoller at redhat dot com>]

One of the most useful tools in debugging prototype hardware is a gadget
called a logic analyser that monitors and records multiple concurrent
time-variant channels of signal states.  One of the most useful
capabilities of a logic analyser is called the "trigger"--a means of
telling the analyser to look for certain conditions and recording what
went on for specifiable intervals before and/or after that condition
occurs.  E.g., you could specify "wait until signal A transits from 0 to
1, then wait for signals BCDE == 1001, then wait 500ns, then stop
recording."  If, e.g., you have the analyser set to show one microsecond
of data, this would result in your "interesting" event being shown in
the middle of the display with 500ns of history and 500ns of following
events surrounding the trigger.


So, the question is whether a similar trigger capability would be useful
for frysk--as part of the new eventviewer I'm writing, I could
incorporate such a thing if anyone wants it.  The really cool software
analog to this is, of course, a regex search and my thought was to
provide a simple menu-driven "wait for a fork event on proc 12345, then
wait 500ms, then show the states of all monitored events on all
monitored threads" thing and a more complex way of entering regexish
kinds of expressions like "((a < (b|c|d)) < e){500ms}" -- "wait for
event 'a' followed by events 'b', 'c', or 'd, followed by event 'e' then
wait 500ms, then show all recorded events."


The same capability could be used to search a recorded event history.


Comments?  Anyone interested?
Chris Moller

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