Re: workqueue testsuite - optional probes

[fche at redhat dot com (Frank Ch. Eigler)]

Hi, Frederic -

> - I met some issues with workqueue tapset:
>    * tracepoints are too old but test testsuite/buildok/irq-detailed.stp succeeds:
>       + testsuite uses "probe workqueue.execute ?" so optional probe.  [...]

We'd need a dejagnu .exp-time divination to see whether the probe should exist,
and skip the test with "untested $test" otherwise.

>       + tapset also uses "?" in definition of the probe. [...]

We mark way too many tapset (and synthetic) probes with ?.  Optionality should be
decided by the end user script, not the tapset.

>    * there are now tracepoints for execution start/end, activation
>    and insertion. There is then no equivalent for creation and
>    destruction. I guess we port then to functions, not tracepoints ?

Could be -- or lament to LKML to get those tracepoints created.
The tapset can define the abstract probe point thusly:

 probe worksomething.something = kernel.trace("something") !,
                                 kernel.function("foo_something") { ... }

Or sometimes in two steps (in case $params are too different to be pulled out
with a common
   if (@defined($par)) par = $par
type code.


>    * trace point "trace_workqueue_execute_start(work)" [...]
> Pass 2: getting a tracepoint query for 1 headers:
>   xxx/omap//include/trace/events/workqueue.h
> ...
> include/trace/events/workqueue.h:37: error: 'struct cpu_workqueue_struct' declared inside parameter list
> include/trace/events/workqueue.h:37: error: its scope is only this definition or declaration, which is probably not what you want

See tapsets.cxx:tracepoint_extra_decls() for hacks sometimes needed
for incomplete kernel headers.

- FChE