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[Bug runtime/3857] New: Flight Recorder on Memory

Currently, the SystemTap?fs module is unloaded when the user
daemon (staprun) exits. I think this behavior is not good for the
flight recorder because the staprun will suddenly be terminated
by being involved in the user space crash.
So I suggest introducing the on-memory flight recorder mode to
the SystemTap. Under this mode, staprun just launches (load and 
run) the kernel module. After that it?fs detached from the 
module soon. If user wants to get the output of this module,
attach the staprun to the module again.

I'll attach a series of the prototype patches which add some options
(see below) to the staprun and the runtime for supporting this feature.
-L: Launch the pre-compiled module and detach form it.
-A: Attach to the detached module. Use without -L.
-D: Detach from the module immediately. Use with -A.

Usage Sample:
1. compile a script.
 $ stap -p4 -k -m flightrec flightrec.stp (you can add '-b' if want)
2. launch the script.
 $ staprun -L flightrec.ko
3. attach, read, and detach
 $ staprun -AD flightrec
4. attach and exit
 $ staprun -A flightrec

I believe this feature is very useful for system administrators
if they use it with the kernel dump mechanism.


           Summary: Flight Recorder on Memory
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: runtime
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: masami dot hiramatsu dot pt at hitachi dot com

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