LTTng » LTTng-tools

Inspection of the enable_events.c code reveals that if the user specifies multiple event types as command options, all but the last one are ignored. A user could specify a list of event names followed by a list of event type options, expecting one-on-one correspondence between them. For example:

lttng enable-event eventone,eventtwo -k --probe probesymbol --function functionsymbol

is equivalent to:

lttng enable-event eventone -k --probe probesymbol
lttng enable-event eventtwo -k --function functionsymbol

Currently the first command actually resolves to:

lttng enable-event eventone -k --function functionsymbol
lttng enable-event eventtwo -k --function functionsymbol

Because allowing multiple event types as well as multiple event names is fraught with difficulties (e.g. what if the two lists are of different lengths?), it should probably be discouraged. Specification of multiple event types in a single enable-event command should be an error condition.

The same observation holds when multiple event types are combined with the --all command option (i.e. 'lttng enable-event -k --all --syscall --tracepoint' is treated the same as 'lttng enable-event -k --all --tracepoint').