[Bug uprobes/17623] Sometimes probes fail to fire events when running against a multi-threaded application

["peter at peca dot dk" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=17623

--- Comment #6 from Peter Allin <peter at peca dot dk> ---
(In reply to David Smith from comment #5)
> On my F20 vm (3.16.3-200.fc20.x86_64), your test program and script worked
> fine (even at WAIT_US 1). What kernel are you running?

That sounds promising :-) I am running a kernel supplied by the Ubuntu project,
they call it "3.13.0-24-generic #47-Ubuntu". I am working remotely today, and
won't risk loosing access to the server by messing a kernel upgrade up (got to
get that remote power switch configured..), but I'll defintely try upgrading it
on monday.

> When you finally stopped systemtap, did it report any skipped probes?

No I haven't seen any such reports. I stop it either by ctrl-c or by running it
under the "timeout" command. Could these ways of stopping it inhibit messages
about skipped probes?

> Depending on what you get with test2.stp, can I ask you to try with HEAD
> systemtap and see what you get?

The behavior is consistent with my version of the script. If I run the
testprogram with the -c option of stap, I gets equals counts. When I run the
test program in the background only "func1" is counted. (I don't know if this
could give any hints, if I switch the order of the probes in the .stp file, it
is "func2" that works).

Given this result, whould it make sense to try out the HEAD systemtap?

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