linux-kernel - Re: [PATCH v9 00/53] fix CONFIG_DRM_USE_DYNAMIC

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Message-ID: <CALwA+NbUCfEj_DzT5eMQ7_pSNpyp-zBe6PEL2XnMZrb303J4_Q@mail.gmail.com>
Date: Fri, 12 Jul 2024 17:44:06 +0200
From: Łukasz Bartosik <ukaszb@...omium.org>
To: jim.cromie@...il.com
Cc: Luis Chamberlain <mcgrof@...nel.org>, daniel.vetter@...ll.ch, 
	tvrtko.ursulin@...ux.intel.com, jani.nikula@...el.com, 
	ville.syrjala@...ux.intel.com, jbaron@...mai.com, gregkh@...uxfoundation.org, 
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	amd-gfx@...ts.freedesktop.org, intel-gvt-dev@...ts.freedesktop.org, 
	intel-gfx@...ts.freedesktop.org, linux@...musvillemoes.dk, joe@...ches.com
Subject: Re: [PATCH v9 00/53] fix CONFIG_DRM_USE_DYNAMIC_DEBUG=y

On Wed, Jul 3, 2024 at 12:14 AM <jim.cromie@...il.com> wrote:
>
> On Tue, Jul 2, 2024 at 4:01 PM Luis Chamberlain <mcgrof@...nel.org> wrote:
> >
> > On Tue, Jul 02, 2024 at 03:56:50PM -0600, Jim Cromie wrote:
> > > This fixes dynamic-debug support for DRM.debug, added via classmaps.
> > > commit bb2ff6c27bc9 (drm: Disable dynamic debug as broken)
> > >
> > > CONFIG_DRM_USE_DYNAMIC_DEBUG=y was marked broken because drm.debug=val
> > > was applied when drm.ko was modprobed; too early for the yet-to-load
> > > drivers, which thus missed the enablement.  My testing with
> > > /etc/modprobe.d/ entries and modprobes with dyndbg=$querycmd options
> > > obscured this omission.
> > >
> > > The fix is to replace invocations of DECLARE_DYNDBG_CLASSMAP with
> > > DYNDBG_CLASSMAP_DEFINE for core, and DYNDBG_CLASSMAP_USE for drivers.
> > > The distinction allows dyndbg to also handle the users properly.
> > >
> > > DRM is the only current classmaps user, and is not really using it,
> > > so if you think DRM could benefit from zero-off-cost debugs based on
> > > static-keys, please test.
> > >
> > > HISTORY
> > >
> > > 9/4/22  - ee879be38bc8..ace7c4bbb240 commited - classmaps-v1 dyndbg parts
> > > 9/11/22 - 0406faf25fb1..16deeb8e18ca commited - classmaps-v1 drm parts
> > >
> > > https://lore.kernel.org/lkml/Y3XUrOGAV4I7bB3M@kroah.com/
> > > greg k-h says:
> > > This should go through the drm tree now.  The rest probably should also
> > > go that way and not through my tree as well.
> >
> > Can't this just be defined as a coccinelle smpl patch? Must easier
> > to read than 53 patches?
> >
>
> perhaps it could - Im not sure that would be easier to review
> than a file-scoped struct declaration or reference per driver
>
> Also, I did it hoping to solicit more Tested-by:s with drm.debug=0x1ff
>
> Jim
>

Jim,

When testing different combinations of Y/M for TEST_DYNAMIC_DEBUG and
TEST_DYNAMIC_DEBUG_SUBMOD in virtme-ng I spotted test failures:

When the TEST_DYNAMIC_DEBUG=M and TEST_DYNAMIC_DEBUG_SUBMOD=M -
BASIC_TESTS, COMMA_TERMINATOR_TESTS, TEST_PERCENT_SPLITTING,
TEST_MOD_SUBMOD selftests passed
When the TEST_DYNAMIC_DEBUG=Y and TEST_DYNAMIC_DEBUG_SUBMOD=M -
BASIC_TESTS, COMMA_TERMINATOR_TESTS selftests passed, however
TEST_PERCENT_SPLITTING selftest fails with ": ./dyndbg_selftest.sh:270
check failed expected 1 on =pf, got 0"
When the TEST_DYNAMIC_DEBUG=Y and TEST_DYNAMIC_DEBUG_SUBMOD=Y -
BASIC_TESTS, COMMA_TERMINATOR_TESTS selftests passed, however
TEST_PERCENT_SPLITTING selftest fails also with ":
./dyndbg_selftest.sh:270 check failed expected 1 on =pf, got 0"

Have I missed something ?

Thanks,
Lukasz

> >   Luis
> >