[lttng-dev] getting a notification from 'lttng start|stop'

[Mathieu Desnoyers]

* McDermott, Andrew (Andrew.McDermott at windriver.com) wrote:
> 
> Is it possible to see when tracing has actually started (i.e., when
> `lttng start' is invoked)?
> 
> I can observe that the tracepoint is enabled/disabled by looking at the
> 'state' field in a 'struct tracepoint'.  Is there an equivalent variable
> to monitor for `lttng start|stop'?  I was trying to dump some additional
> process state (via calls to tracepoint) whenever an external
> start/stop/start/stop/start sequence occurs.

statedump for UST. This is a feature we don't have at this point. It
would need to be designed within UST. I don't this a simple "hack" would
do.

> 
> Also, when I run 'lttng enable-event -u -a' I see that the 'state' value
> changes from '0' to '1', but if I run 'lttng disable-event -u -a' it
> stays at '1'.  Is this expected?  If I subsequently run 'lttng destroy'
> then it does go to '0'.  Shouldn't the disable set it to '0' too?

I think it's been fixed, but if you still experience this issue, please
file a bug report on bugs.lttng.org.

Thanks,

Mathieu

> 
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> andy
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com