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[Bug runtime/6030] stap, staprun, stapio interaction quirks: stale module left unloaded
- From: "fche at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sources dot redhat dot com
- Date: 4 Apr 2008 11:18:40 -0000
- Subject: [Bug runtime/6030] stap, staprun, stapio interaction quirks: stale module left unloaded
- References: <20080404085514.6030.ananth@in.ibm.com>
- Reply-to: sourceware-bugzilla at sourceware dot org
------- 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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