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

[masami dot hiramatsu dot pt at hitachi dot com]

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
 ^C

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

thanks,

-- 
           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


http://sourceware.org/bugzilla/show_bug.cgi?id=3857

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