On 06/27/2012 08:33 PM, Mathieu Desnoyers wrote:
hrm, although possibly interesting, I don't think this semantic follows
the lttng UI event enabling semantic. There are a few use-cases to
cover:
1) enable tracepoints, start tracing, run app.
2) enable some tracepoints, start tracing, run app, enable more
tracepoints while app is running.
3) start tracing, run app, enable all tracepoints while app is running.
AFAIU, your patch and proposed semantic covers use-case #1, but breaks
the other 2. Basically, we have to apply a logical "or" between each
enable-event command (rather than an "and" as your proposed semantic
suggests), because they can be applied independently.
You are right, I only had use-case #1 in mind when I wrote this patch. I
intentionally kept my modifications small not to break any of the the
existing functionality if "!" is not used.
Let me provide a more elaborate description of what this patch is doing:
Original behavior:
match_wildcard():
Check if a wildcard_entry matches the given lttng_event_desc name.
If a mach is found and the loglevel also matches return the
wildcard_entry. Otherwise return 0.
ltt_event_create():
If an event with the given name does not already exist create one,
pass a pointer to it (via _event) and return 0. If an event with the
given name already exists return -EEXIST.
Behavior after patch:
match_wildcard():
First check if there is a wildcard_entry that starts with "!" that
matches the given lttng_event_desc name. If a filter matches return 0
(no match). If not proceed as before.
ltt_event_create():
If an event should be created that starts with "!" do not create it
but instead add a new wildcard_entry (if not already existing in the
wildcard_list). Otherwise as before.
Note that the change of ltt_event_create() was necessary to make sure
that also things like:
lttng enable-event -u -c met_tools --tracepoint '!met_func:enter'
work (i.e. filters that do not have a '*' at the end).
We could however try to come up with an event attribute that gets
applied on a specific event, e.g.:
lttng enable-event -u -a --exclude 'met_func:*' --exclude 'met_call:*'
I would prefer your "--exclude" over my solution but I doubt that I
could implement it properly. Are you planning to add "--exclude"
yourself or could you provide me with detailed instructions how to
implement it (which functions and structures need to be adapted).
--
Thanks,
Paul
--
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