Hi David, Yes you are right. I've opened a bug for that. You might want to subscribe to it :).
https://bugs.lttng.org/issues/391 Thanks a lot! David David OShea: > Hi David, Mathieu, > >> -----Original Message----- >> From: David Goulet [mailto:[email protected]] >> Sent: Wednesday, 31 October 2012 7:05 AM >> To: Mathieu Desnoyers >> Cc: David OShea; [email protected] >> Subject: Re: [lttng-dev] 'add-context --userspace' must be preceded by >> 'enable-channel' or 'enable-event' > [...] >> Mathieu Desnoyers: >>> If I understand correctly, the two use-cases where you issue >>> "add-context" prior to enable-event and prior to enable-channel are >>> behaving as if they are failing (those contexts don't appear in the >>> trace), but you don't get any error message. David (David Goulet, in >>> CC), any clue on why lttng-tools behaves that way, and how can we fix >>> this ? > > This is not quite correct: I don't have a use case where I 'add-context' > prior to 'enable-channel'. The only case that fails is when I do an > 'add-context' immediately after 'create'. Things work properly if I do an > 'enable-channel' or 'enable-event' before the 'add-context'. > >>>> Bad: 'add-context' before 'enable-event': >>>> >>>> """ >>>> # lttng create >>>> Session auto-20121029-090142 created. >>>> Traces will be written in /root/lttng-traces/auto-20121029-090142 >>>> # lttng add-context --userspace -t vpid -t vtid -t procname >>>> UST context procname added to all channels >>>> UST context vtid added to all channels >>>> UST context vpid added to all channels >>>> # lttng enable-event --userspace --all >> >> The context is added to "channel0" here which is the default one >> created >> automatically. >> >> The lttng-tools session daemon do add the contexts to the channel on >> the >> tracer side (ustctl_add_context) so Mathieu we might want to check if >> the UST tracer do behave correctly by adding the context to all events >> of a channel. (Note here that -a -u was used hence the "*" event). >> >> I also do confirm that lttng-tools is doing the right ustctl call on >> channel0 here. > > I took a quick look at the source for lttng-tools 2.0.4 and 2.1.0-rc4, and it > looks to me like in the case above, the default channel "channel0" is not > actually created by 'add-context'. > > In lttng_enable_event(), if no channel name was specified, it uses > DEFAULT_CHANNEL_NAME, then in cmd_enable_event_all() (I'm considering the > case of enabling all events, which is what I do), in case LTTNG_DOMAIN_UST, > if the specified channel doesn't exist, it will create it. This seems to be > why doing the 'enable-event' first works. > > On the other hand, in lttng_add_context(), if no channel name is specified, > no channel name is passed to the server, then in cmd_add_context(), > context_ust_add() is called, and in that function, if no channel name is > specified, it adds the context to every channel. However, my understanding > is that at this point there are no channels created. > > Apologies if I have missed anything here! > > Regards, > David > > ---------------------------------------------------------------------- > The information contained in this transmission may be confidential. Any > disclosure, copying, or further distribution of confidential information is > not permitted unless such privilege is explicitly granted in writing by > Quantum. Quantum reserves the right to have electronic communications, > including email and attachments, sent across its networks filtered through > anti virus and spam software programs and retain such messages in order to > comply with applicable data security and retention requirements. Quantum is > not responsible for the proper and complete transmission of the substance of > this communication or for any delay in its receipt. _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
