Re: [igt-dev] [PATCH i-g-t] lib/igt_core: Enable extra kernel logs for audio debug

[Ashutosh Dixit <ashutosh.dixit@intel.com>]

On Thu, 14 Mar 2019 03:12:25 -0700, Jani Nikula wrote:
>
> On Wed, 13 Mar 2019, Ashutosh Dixit <ashutosh.dixit@intel.com> wrote:
> >
> > For debug of audio issues in power management and driver reload tests,
> > additional kernel logs may be useful, both in dmesg as well as
> > ftrace. Add the infrastructure to generate these logs which can be
> > enabled/disabled at sub-test granularity. Also enable these logs for
> > selected sub-tests. The ftrace buffer is dumped to stdout to avoid
> > changes in igt_runner and other CI infrastructure.
>
> I think I'd just provide the helpers and add them in igt_fixture instead
> of introducing new "extra klog" subtest helpers. I don't think we need
> that granularity.

Actually the v1 commit message is misleading. The real reason for the
"subtest granularity" is mentioned in the v2 commit message:

    "At present igt_runner and other CI infrastructure does not capture the
    ftrace buffer. Therefore, to avoid changes to igt_runner and the CI
    infrastructure the ftrace buffer is dumped to stdout. This is done
    after each sub-test so the ftrace output for a subtest can be
    associated with that subtest."

> OTOH I think we do need more granularity in enabling the dynamic debug
> and the tracing separately.

I think there is no real way to enable such granularity with the approach
taken in this patch. Dynamic debug and tracing functions can be separated
out. But there will have to be a single function which enables both of
these together as has been done here. Unless we change the approach taken
here. But then what is that approach?

> The *skl* style wildcard dynamid debug enables/disables also seem not
> specific enough.

Perhaps something like this is better?

echo "file drivers/sound/soc/intel/skylake/* +p" > \
     <debugfs>/dynamic_debug/control

> Another review comment: Please don't use system(). Implement this in C,
> not shell script

Agreed. But let us agree on the overall approach taken in this patch first
and also take Chris' patch into account. If we are in agreement about the
high level approach making such changes is not an issue.

Please note that this patch is in response to the request to generate the
sort of logs mentioned in [1] in CI, so that hard to reproduce audio issues
can be debugged.

Thanks for the reviews!

[1] https://bugs.freedesktop.org/show_bug.cgi?id=109189#c4

--
Ashutosh Dixit, Intel Open Source Graphics Center
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