[Bug runtime/6030] stap, staprun, stapio interaction quirks: stale module left unloaded

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-04-04 11:18 -------
We cannot reasonably recover from a kill -9 on staprun.  That is the only
privileged process that can unload the module.  It may have been hand-started,
leaving none of our code available to watch over it and restart it.  Teaching
stap to re-fork staprun another time is perhaps possible, but in your
"kill -9 stap staprun" scenario, that wouldn't help either.

Note when the module detects its user-space partner process going away, it
carries out shutdown as far as it can: deregisters probes, frees memory.
A module cannot unload itself AFAIK.  So while it is an orphan, it merely
sits in memory, and probably blocks a repeat invocation.  It's not that bad.

Perhaps it's time to reconsider including a script such as
http://sourceware.org/ml/systemtap/2008-q1/msg00051.html
in the distribution.  Or a cron-driven systemtap module cleaner/unloader.


-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=6030

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