[PATCH v2 0/2] drm/todo: Add section for GPU Scheduler

[PATCH v2 0/2] drm/todo: Add section for GPU Scheduler

[Philipp Stanner]

Changes in v2:
  - Fix wrong list item index in patch 1.

The GPU Scheduler has enough problems to be covered by the drm todo
list. Let's add an entry.

This series is the succesor of [1].

[1] https://lore.kernel.org/dri-devel/20251023143031.149496-2-phasta@kernel.org/

Philipp Stanner (2):
  drm/todo: Add section with task for GPU scheduler
  drm/todo: Add entry for unlocked drm/sched rq readers

 Documentation/gpu/todo.rst | 45 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

-- 
2.49.0

[PATCH v2 1/2] drm/todo: Add section with task for GPU scheduler

[Philipp Stanner]

The GPU scheduler has a great many problems and deserves its own TODO
section.

Add a section and a first task describing the problem of
drm_sched_resubmit_jobs() being deprecated without a successor.

Signed-off-by: Philipp Stanner <phasta@kernel.org>
---
 Documentation/gpu/todo.rst | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 9013ced318cb..084e148e78c1 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -878,6 +878,37 @@ Contact: Christian König
 
 Level: Starter
 
+DRM GPU Scheduler
+=================
+
+Provide a universal successor for drm_sched_resubmit_jobs()
+------------------------------------------------------------
+
+drm_sched_resubmit_jobs() is deprecated. Main reason being that it leads to
+reinitializing dma_fences. See that function's docu for details. The better
+approach for valid resubmissions by amdgpu and Xe is (apparently) to figure out
+which job (and, through association: which entity) caused the hang. Then, the
+job's buffer data, together with all other jobs' buffer data currently in the
+same hardware ring, must be invalidated. This can for example be done by
+overwriting it. amdgpu currently determines which jobs are in the ring and need
+to be overwritten by keeping copies of the job. Xe obtains that information by
+directly accessing drm_sched's pending_list.
+
+Tasks:
+
+1. implement scheduler functionality through which the driver can obtain the
+   information which *broken* jobs are currently in the hardware ring.
+2. Such infrastructure would then typically be used in
+   drm_sched_backend_ops.timedout_job(). Document that.
+3. Port a driver as first user.
+4. Document the new alternative in the docu of deprecated
+   drm_sched_resubmit_jobs().
+
+Contact: Christian König <ckoenig.leichtzumerken@gmail.com>
+         Philipp Stanner <phasta@kernel.org>
+
+Level: Advanced
+
 Outside DRM
 ===========
 
-- 
2.49.0

[PATCH v2 2/2] drm/todo: Add entry for unlocked drm/sched rq readers

[Philipp Stanner]

Runqueues are currently almost everywhere being read unlocked in
drm/sched. At XDC 2025, the assembled developers were unsure whether
that's legal and whether it can be fixed. Someone should find out.

Add a todo entry for the unlocked runqueue reader problem.

Signed-off-by: Philipp Stanner <phasta@kernel.org>
---
 Documentation/gpu/todo.rst | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 084e148e78c1..fc8bafd593d8 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -909,6 +909,20 @@ Contact: Christian König <ckoenig.leichtzumerken@gmail.com>
 
 Level: Advanced
 
+Add locking for runqueues
+-------------------------
+
+There is an old FIXME by Sima in include/drm/gpu_scheduler.h. It details that
+struct drm_sched_rq is read at many places without any locks, not even with a
+READ_ONCE. At XDC 2025 no one could really tell why that is the case, whether
+locks are needed and whether they could be added. (But for real, that should
+probably be locked!). Check whether it's possible to add locks everywhere, and
+do so if yes.
+
+Contact: Philipp Stanner <phasta@kernel.org>
+
+Level: Intermediate
+
 Outside DRM
 ===========
 
-- 
2.49.0

Re: [PATCH v2 0/2] drm/todo: Add section for GPU Scheduler

[Philipp Stanner]

+Cc Matthew, Tvrtko, Christian

On Fri, 2025-11-07 at 14:56 +0100, Philipp Stanner wrote:
> Changes in v2:
>   - Fix wrong list item index in patch 1.
> 
> The GPU Scheduler has enough problems to be covered by the drm todo
> list. Let's add an entry.
> 
> This series is the succesor of [1].
> 
> [1] https://lore.kernel.org/dri-devel/20251023143031.149496-2-phasta@kernel.org/
> 
> Philipp Stanner (2):
>   drm/todo: Add section with task for GPU scheduler
>   drm/todo: Add entry for unlocked drm/sched rq readers

Can someone give this series a review please?

Thx,
P.

Re: [PATCH v2 0/2] drm/todo: Add section for GPU Scheduler

[Dave Airlie]

Acked-by: Dave Airlie <airlied@redhat.com>

On Thu, 27 Nov 2025 at 22:50, Philipp Stanner <phasta@mailbox.org> wrote:
>
> +Cc Matthew, Tvrtko, Christian
>
> On Fri, 2025-11-07 at 14:56 +0100, Philipp Stanner wrote:
> > Changes in v2:
> >   - Fix wrong list item index in patch 1.
> >
> > The GPU Scheduler has enough problems to be covered by the drm todo
> > list. Let's add an entry.
> >
> > This series is the succesor of [1].
> >
> > [1] https://lore.kernel.org/dri-devel/20251023143031.149496-2-phasta@kernel.org/
> >
> > Philipp Stanner (2):
> >   drm/todo: Add section with task for GPU scheduler
> >   drm/todo: Add entry for unlocked drm/sched rq readers
>
> Can someone give this series a review please?
>
> Thx,
> P.

Re: [PATCH v2 0/2] drm/todo: Add section for GPU Scheduler

[Philipp Stanner]

On Tue, 2025-12-02 at 17:37 +1000, Dave Airlie wrote:
> Acked-by: Dave Airlie <airlied@redhat.com>
> 
> On Thu, 27 Nov 2025 at 22:50, Philipp Stanner <phasta@mailbox.org> wrote:
> > 
> > +Cc Matthew, Tvrtko, Christian
> > 
> > On Fri, 2025-11-07 at 14:56 +0100, Philipp Stanner wrote:
> > > Changes in v2:
> > >   - Fix wrong list item index in patch 1.
> > > 
> > > The GPU Scheduler has enough problems to be covered by the drm todo
> > > list. Let's add an entry.
> > > 
> > > This series is the succesor of [1].
> > > 
> > > [1] https://lore.kernel.org/dri-devel/20251023143031.149496-2-phasta@kernel.org/
> > > 
> > > Philipp Stanner (2):
> > >   drm/todo: Add section with task for GPU scheduler
> > >   drm/todo: Add entry for unlocked drm/sched rq readers

Pushed to drm-misc-next

P.