linux-kernel - Re: [PATCH v2 00/17] drm: cleanup: Use DRM_MODESET_LOCK_ALL

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Date:   Sat, 2 Oct 2021 01:05:47 +0300
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     Sean Paul <sean@...rly.run>
Cc:     Fernando Ramos <greenfoo@....eu>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        nouveau@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH v2 00/17] drm: cleanup: Use DRM_MODESET_LOCK_ALL_*
 helpers where possible

On Fri, Oct 01, 2021 at 04:48:15PM -0400, Sean Paul wrote:
> On Fri, Oct 01, 2021 at 10:00:50PM +0300, Ville Syrjälä wrote:
> > On Fri, Oct 01, 2021 at 02:36:55PM -0400, Sean Paul wrote:
> > > On Fri, Sep 24, 2021 at 08:43:07AM +0200, Fernando Ramos wrote:
> > > > Hi all,
> > > > 
> > > > One of the things in the DRM TODO list ("Documentation/gpu/todo.rst") was to
> > > > "use DRM_MODESET_LOCAL_ALL_* helpers instead of boilerplate". That's what this
> > > > patch series is about.
> > > > 
> > > > You will find two types of changes here:
> > > > 
> > > >   - Replacing "drm_modeset_lock_all_ctx()" (and surrounding boilerplate) with
> > > >     "DRM_MODESET_LOCK_ALL_BEGIN()/END()" in the remaining places (as it has
> > > >     already been done in previous commits such as b7ea04d2)
> > > > 
> > > >   - Replacing "drm_modeset_lock_all()" with "DRM_MODESET_LOCK_ALL_BEGIN()/END()"
> > > >     in the remaining places (as it has already been done in previous commits
> > > >     such as 57037094)
> > > >     
> > > > Most of the changes are straight forward, except for a few cases in the "amd"
> > > > and "i915" drivers where some extra dancing was needed to overcome the
> > > > limitation that the DRM_MODESET_LOCK_ALL_BEGIN()/END() macros can only be used
> > > > once inside the same function (the reason being that the macro expansion
> > > > includes *labels*, and you can not have two labels named the same inside one
> > > > function)
> > > > 
> > > > Notice that, even after this patch series, some places remain where
> > > > "drm_modeset_lock_all()" and "drm_modeset_lock_all_ctx()" are still present,
> > > > all inside drm core (which makes sense), except for two (in "amd" and "i915")
> > > > which cannot be replaced due to the way they are being used.
> > > > 
> > > > Changes in v2:
> > > > 
> > > >   - Fix commit message typo
> > > >   - Use the value returned by DRM_MODESET_LOCK_ALL_END when possible
> > > >   - Split drm/i915 patch into two simpler ones
> > > >   - Remove drm_modeset_(un)lock_all()
> > > >   - Fix build problems in non-x86 platforms
> > > > 
> > > > Fernando Ramos (17):
> > > >   drm: cleanup: drm_modeset_lock_all_ctx() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/i915: cleanup: drm_modeset_lock_all_ctx() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/msm: cleanup: drm_modeset_lock_all_ctx() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN() drm/vmwgfx: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/tegra: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/shmobile: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/radeon: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/omapdrm: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/nouveau: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/msm: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/i915: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/i915: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN() part 2
> > > >   drm/gma500: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm/amd: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()
> > > >   drm: cleanup: remove drm_modeset_(un)lock_all()
> > > >   doc: drm: remove TODO entry regarding DRM_MODSET_LOCK_ALL cleanup
> > > > 
> > > 
> > > Thank you for revising, Fernando! I've pushed the set to drm-misc-next (along
> > > with the necessary drm-tip conflict resolutions).
> > 
> > Ugh. Did anyone actually review the locking changes this does?
> > I shot the previous i915 stuff down because the commit messages
> > did not address any of it.
> 
> I reviewed the set on 9/17, I didn't see your feedback on that thread.

It was much earlir than that.
https://lists.freedesktop.org/archives/dri-devel/2021-June/313193.html

And I think I might have also shot down a similar thing earlier.

I was actually half considering sending a patch to nuke that
misleading TODO item. I don't think anything which changes
which locks are taken should be considred a starter level task.
And the commit messages here don't seem to address any of it.

-- 
Ville Syrjälä
Intel