[lttng-dev] Problem with adding vpid and vtid context to UST

[David OShea]

> -----Original Message-----
> From: David Goulet [mailto:dgoulet at efficios.com]
> Sent: Tuesday, 18 June 2013 5:32 AM
> To: Amit Margalit
> Cc: lttng-dev at lists.lttng.org
> Subject: Re: [lttng-dev] Problem with adding vpid and vtid context to
> UST
> 
> Hi Amit,
> 
> Amit Margalit:
> > Hi,
> >
> > Every time I try this, I get the following error:
> >
> > Error: Error starting tracing for app pid: 5663 (ret: -1027)
> >
> > Here's my sequence:
> >
> > lttng create foo -o /store/
> > lttng enable-channel -u
> > lttng add-context -u -t vpid -t vtid -t procname
> > lttng enable-event -u -a
> > lttng start foo
> >
> > At this point I start my application and get that error. When the
> application
> > exits, I stop the tracing, and run lttng view.
> >
> > The trace session seems to have worked just fine, and "procname" was
> indeed
> > added to the context, but vtid and vpid were not.
> 
> What's going on here is that you enable a channel then add contexts.
> This is
> perfectly OK (although your example is missing a channel name). So, the
> following "lttng enable-event" creates a default channel "channel0"
> since no
> "-c" was specified.
> 
> So basically, the contexts are available on the first channel and not
> the second
> one.

Not that it's very important, but another option: aside from the missing channel name, I've used the above sequence of commands with both LTTng 2.0.x and 2.1.x with success.  For 'enable-channel', I specified the channel name "channel0" so that the context was added to the same channel that the subsequent 'enable-event' acted on.
 
Regards,
David

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