On 15-Aug 11:37, Dietmar Eggemann wrote:

On 08/14/2018 06:49 PM, Patrick Bellasi wrote:

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Hi Dietmar!

On 14-Aug 17:44, Dietmar Eggemann wrote:

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On 08/06/2018 06:39 PM, Patrick Bellasi wrote:

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This one indicates that there are some holes in your ref-counting.

Not really, this has been added not because I've detected a refcount
issue... but because it was suggested as a possible safety check in a
previous code review comment:

   https://lore.kernel.org/lkml/20180720151156.GA31421@e110439-lin/ (local)

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It's probably easier to debug that there is still a task but the
uc_grp[group_id].tasks value == 0 (A). I assume the other problem exists as
well, i.e. last task and uc_grp[group_id].tasks > 1 (B)?

You have uclamp_cpu_[get/put](_id)() in [enqueue/dequeue]_task.

Patch 04/14 introduces its use in uclamp_task_update_active().

Do you know why (A) (and (B)) are happening?

I've never saw that warning in my tests so far so, again, the warning
is there just to support testing/debugging when refcounting code
is/will be touched in the future. That's also the reason why is
SCHED_DEBUG protected.

Ah, OK, I thought you really see it more often and that it also relate to
Pavan's comment on 02/14 about the missing treatment of exiting tasks.

If this is only for testing/debugging, I would suggest a simple one line
BUG_ON()

These are (eventually) considered as recoverable errors... thus,
AFAIK, using BUG_ON is overkilling and discouraged:
  https://elixir.bootlin.com/linux/latest/source/include/asm-generic/bug.h#L42

You find CONFIG_SCHED_DEBUG=y in production kernels as well.

AFAIK, that setting is discouraged for production kernels...
Moreover, it's still better to WARN sometimes on a production kernel
the crash the device, isnt't it?

-- 
#include <best/regards.h>

Patrick Bellasi