Hi Ashley,
On 10/04/2025 13:57, Ashley Smith wrote:
> The timeout logic provided by drm_sched leads to races when we try
> to suspend it while the drm_sched workqueue queues more jobs. Let's
> overhaul the timeout handling in panthor to have our own delayed work
> that's resumed/suspended when a group is resumed/suspended. When an
> actual timeout occurs, we call drm_sched_fault() to report it
> through drm_sched, still. But otherwise, the drm_sched timeout is
> disabled (set to MAX_SCHEDULE_TIMEOUT), which leaves us in control of
> how we protect modifications on the timer.
>
> One issue seems to be when we call drm_sched_suspend_timeout() from
> both queue_run_job() and tick_work() which could lead to races due to
> drm_sched_suspend_timeout() not having a lock. Another issue seems to
> be in queue_run_job() if the group is not scheduled, we suspend the
> timeout again which undoes what drm_sched_job_begin() did when calling
> drm_sched_start_timeout(). So the timeout does not reset when a job
> is finished.
>
> Co-developed-by: Boris Brezillon <boris.brezil...@collabora.com>
> Signed-off-by: Boris Brezillon <boris.brezil...@collabora.com>
> Tested-by: Daniel Stone <dani...@collabora.com>
> Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block")
> Signed-off-by: Ashley Smith <ashley.sm...@collabora.com>
> ---
> drivers/gpu/drm/panthor/panthor_sched.c | 244 +++++++++++++++++-------
> 1 file changed, 177 insertions(+), 67 deletions(-)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c
> b/drivers/gpu/drm/panthor/panthor_sched.c
> index 446ec780eb4a..32f5a75bc4f6 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
[...]
> @@ -2727,8 +2784,17 @@ void panthor_sched_suspend(struct panthor_device
> *ptdev)
> * automatically terminate all active groups, so let's
> * force the state to halted here.
> */
> - if (csg_slot->group->state !=
> PANTHOR_CS_GROUP_TERMINATED)
> + if (csg_slot->group->state !=
> PANTHOR_CS_GROUP_TERMINATED) {
> csg_slot->group->state =
> PANTHOR_CS_GROUP_TERMINATED;
> +
> + /* Reset the queue slots manually if the
> termination
> + * request failed.
> + */
> + for (i = 0; i < group->queue_count; i++) {
> + if (group->queues[i])
> + cs_slot_reset_locked(ptdev,
> csg_id, i);
> + }
> + }
> slot_mask &= ~BIT(csg_id);
> }
> }
So this seems to be the only change from v2 (a changelog can be
helpful!). And I'm not convinced it belongs in this patch? It's not just
"[making] the timeout per-queue instead of per-job".
I haven't dug through the details, but I think this belongs in a
separate patch.
Thanks,
Steve
