Re: [Nouveau] [PATCH] drm/nouveau: Drop mutex_lock_nested for atomic

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Sep 30, 2020 at 10:45:05AM +1000, Ben Skeggs wrote:
> On Wed, 30 Sep 2020 at 00:52, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > On Thu, Sep 17, 2020 at 3:15 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > >
> > > Ben, did you have a chance to look at this?
> >
> > Ping
> > -Daniel
> >
> > > On Mon, Aug 3, 2020 at 1:22 PM Maarten Lankhorst
> > > <maarten.lankhorst@linux.intel.com> wrote:
> > > >
> > > > Op 02-08-2020 om 20:18 schreef Daniel Vetter:
> > > > > Purely conjecture, but I think the original locking inversion with the
> > > > > legacy page flip code between flipping and ttm's bo move function
> > > > > shoudn't exist anymore with atomic: With atomic the bo pinning and
> > > > > actual modeset commit is completely separated in the code patsh.
> > > > >
> > > > > This annotation was originally added in
> > > > >
> > > > > commit 060810d7abaabcab282e062c595871d661561400
> > > > > Author: Ben Skeggs <bskeggs@redhat.com>
> > > > > Date:   Mon Jul 8 14:15:51 2013 +1000
> > > > >
> > > > >     drm/nouveau: fix locking issues in page flipping paths
> > > > >
> > > > > due to
> > > > >
> > > > > commit b580c9e2b7ba5030a795aa2fb73b796523d65a78
> > > > > Author: Maarten Lankhorst <m.b.lankhorst@gmail.com>
> > > > > Date:   Thu Jun 27 13:48:18 2013 +0200
> > > > >
> > > > >     drm/nouveau: make flipping lockdep safe
> > > > >
> > > > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > > > Cc: Maarten Lankhorst <m.b.lankhorst@gmail.com>
> > > > > Cc: Ben Skeggs <bskeggs@redhat.com>
> > > > > Cc: Dave Airlie <airlied@gmail.com>
> > > > > Cc: nouveau@lists.freedesktop.org
> > > > > ---
> > > > > I might be totally wrong, so this definitely needs testing :-)
> > > > >
> > > > > Cheers, Daniel
> > > > > ---
> > > > >  drivers/gpu/drm/nouveau/nouveau_bo.c | 6 +++++-
> > > > >  1 file changed, 5 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> > > > > index 7806278dce57..a7b2a9bb0ffe 100644
> > > > > --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> > > > > +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> > > > > @@ -776,7 +776,11 @@ nouveau_bo_move_m2mf(struct ttm_buffer_object *bo, int evict, bool intr,
> > > > >                       return ret;
> > > > >       }
> > > > >
> > > > > -     mutex_lock_nested(&cli->mutex, SINGLE_DEPTH_NESTING);
> > > > > +     if (drm_drv_uses_atomic_modeset(drm->dev))
> > > > > +             mutex_lock(&cli->mutex);
> > > > > +     else
> > > > > +             mutex_lock_nested(&cli->mutex, SINGLE_DEPTH_NESTING);
> > > > > +
> > > > >       ret = nouveau_fence_sync(nouveau_bo(bo), chan, true, intr);
> > > > >       if (ret == 0) {
> > > > >               ret = drm->ttm.move(chan, bo, &bo->mem, new_reg);
> > > >
> > > > Well if you're certain it works now. :)
> > > >
> > > > Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Acked-by: Ben Skeggs <bskeggs@redhat.com>

Can you pull this in through your tree and maybe give it a spin just to
make sure? I don't really have nouveau hardware here.

Also it's entirely stand-alone, I was simply reviewing all the
mutex_lock_nested we have in drm, and this one stuck out as probably not
necessary anymore, at least with atomic.

I guess I can also just stuff it into drm-misc-next and if it blows up,
figure out what to do then :-)
-Daniel

> 
> > > >
> > >
> > >
> > > --
> > > Daniel Vetter
> > > Software Engineer, Intel Corporation
> > > http://blog.ffwll.ch
> >
> >
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch
> > _______________________________________________
> > Nouveau mailing list
> > Nouveau@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/nouveau

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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