[PATCH] drm/xe/ufence: Flush xe ordered_wq in case of ufence timeout

[Matthew Brost]

On Wed, Oct 23, 2024 at 05:58:17PM +0200, Nirmoy Das wrote:
> Flush xe ordered_wq in case of ufence timeout which is observed
> on LNL and that points recent scheduling issue with E-cores.
> 
> This is similar to the recent fix:
> commit e51527233804 ("drm/xe/guc/ct: Flush g2h worker in case of g2h
> response timeout") and should be removed once there is E core
> scheduling fix.
> 
> Cc: Badal Nilawar <badal.nilawar at intel.com>
> Cc: Matthew Auld <matthew.auld at intel.com>
> Cc: John Harrison <John.C.Harrison at Intel.com>
> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
> Cc: Lucas De Marchi <lucas.demarchi at intel.com>

Seems like a reasonable W/A for now which I think we want in 6.12 too.
I'd follow up with the maintainer who is doing our 6.12 PR to make sure
this gets in.

With that:
Reviewed-by: Matthew Brost <matthew.brost at intel.com>

> Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/2754
> Suggested-by: Matthew Brost <matthew.brost at intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_wait_user_fence.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_wait_user_fence.c b/drivers/gpu/drm/xe/xe_wait_user_fence.c
> index f5deb81eba01..7f034871345b 100644
> --- a/drivers/gpu/drm/xe/xe_wait_user_fence.c
> +++ b/drivers/gpu/drm/xe/xe_wait_user_fence.c
> @@ -155,6 +155,17 @@ int xe_wait_user_fence_ioctl(struct drm_device *dev, void *data,
>  		}
>  
>  		if (!timeout) {
> +			/*
> +			 * This is analogous to e51527233804 ("drm/xe/guc/ct: Flush g2h worker
> +			 * in case of g2h response timeout")
> +			 *
> +			 * TODO: Drop this change once workqueue scheduling delay issue is
> +			 * fixed on LNL Hybrid CPU.
> +			 */
> +			__flush_workqueue(xe->ordered_wq);
> +			err = do_compare(addr, args->value, args->mask, args->op);
> +			if (err <= 0)
> +				break;
>  			err = -ETIME;
>  			break;
>  		}
> -- 
> 2.46.0
>