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

McDermott, Andrew Andrew.McDermott at windriver.com
Thu Oct 25 07:49:41 EDT 2012

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.

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?


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