[Bug runtime/16409] New: can't re-attach when using flight-recorder/detach mode and -c CMD together

["jlebon at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=16409

            Bug ID: 16409
           Summary: can't re-attach when using flight-recorder/detach mode
                    and -c CMD together
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
          Assignee: systemtap at sourceware dot org
          Reporter: jlebon at redhat dot com

It is currently not possible to combine the stap -F switch (or staprun -L
switch) with the -c switch. More specifically, inserting a module in
flight-recorder/detach mode and simultaneously running a -c CMD will cause
stapio to keep running (to spawn/wait the CMD) and thus make it impossible to
re-attach to the module later on.

For example:

[root@vm ~]# stap -e 'probe process.function("main") { println("entered main")
}' -c echo -m echomod -F
Disconnecting from systemtap module.
To reconnect, type "staprun -A echomod"
[root@vm ~]# staprun -A echomod
ERROR: Cannot attach to module echomod control channel; not running?
[root@vm ~]# ps aux | grep stapio
root      1711  0.0  0.0 110096   112 pts/0    S    16:08   0:00
/usr/libexec/systemtap/stapio -c echo -L /tmp/stapSmZInN/echomod.ko -F4
[root@vm ~]#

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