[lttng-dev] [BUG] lttng-sessiond

[Hannes Weisbach]

>> However, loading multiple probes with
>> either --kmod-probes or --extra-kmod-probes still does not work:
>> $ sudo lttng-sessiond -vvv --extra-kmod-probes=sched,napi
>> [...]
>> DEBUG1 - 11:42:18.492870 [5358/5358]: Modprobe successfully lttng-probe-napi
>> (in modprobe_lttng() at modprobe.c:285)
>> sh: 1: Syntax error: "(" unexpected
>> DEBUG1 - 11:42:18.495037 [5358/5358]: Unable to load optional module (null);
>> continuing (in modprobe_lttng() at modprobe.c:281)
>> [...]
> 
> Why do you need to load those explicitly ? They should be
> already loaded by default. I don't get those errors here.
I don't need them.  They're just examples.  Albeit they are loaded by
default, using --kmod-probes or --extra-kmod-probes should work, no?

> Which shell are you using (sh symlink) ? Can you reproduce
> using bash ?
I added a bit of debug output, namely the string that gets passed to
system(): DBG("system(%s)", modprobe);

Result:
$ sudo lttng-sessiond -vvv --kmod-probes="sched,napi"
[…]
DEBUG1 - 16:02:21.372257 [4227/4227]: system(/sbin/modprobe -q lttng-probe-napi) (in modprobe_lttng() at modprobe.c:263)
DEBUG1 - 16:02:21.381980 [4227/4227]: Modprobe successfully lttng-probe-napi (in modprobe_lttng() at modprobe.c:286)
DEBUG1 - 16:02:21.382306 [4227/4227]: system(/sbin/modprobe -q (null)) (in modprobe_lttng() at modprobe.c:263)
sh: 1: Syntax error: "(" unexpected
DEBUG1 - 16:02:21.384942 [4227/4227]: Unable to load optional module (null); continuing (in modprobe_lttng() at modprobe.c:282)

The problem is not with sh.  It is that a NULL pointer is passed to
snprintf in modprobe.c:254.  My guess is, that splitting the argument
of --kmod-probes and --extra-kmod-probes (probably using strtok) is
somehow broken.  If you can tell where in the source of lttng-sessiond
argument parsing happens I can step through the code to see what
is going on.

Best regards,
Hannes
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 203 bytes
Desc: Message signed with OpenPGP using GPGMail
URL: <http://lists.lttng.org/pipermail/lttng-dev/attachments/20150425/6d8a7685/attachment.sig>