Re: [PATCH] drm/xe: Don't restart parallel queues multiple times on GT reset

[Matthew Brost <matthew.brost@intel.com>]

On Mon, Oct 21, 2024 at 11:11:46PM +0200, Nirmoy Das wrote:
> In case of parallel submissions multiple GuC id will point to the
> same exec queue and on GT reset such exec queues will get restarted
> multiple times which is not desirable.
> 
> Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/2295
> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Tejas Upadhyay <tejas.upadhyay@intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_submit.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
> index 0b81972ff651..6aeb007eaf06 100644
> --- a/drivers/gpu/drm/xe/xe_guc_submit.c
> +++ b/drivers/gpu/drm/xe/xe_guc_submit.c
> @@ -1784,8 +1784,13 @@ int xe_guc_submit_start(struct xe_guc *guc)
>  
>  	mutex_lock(&guc->submission_state.lock);
>  	atomic_dec(&guc->submission_state.stopped);
> -	xa_for_each(&guc->submission_state.exec_queue_lookup, index, q)
> +	xa_for_each(&guc->submission_state.exec_queue_lookup, index, q) {
> +		/* Skip restarting parallel queues */
> +		if (exec_queue_enabled(q) && xe_exec_queue_is_parallel(q))
> +			continue;

This doesn't look right as exec_queue_enabled can race here...

I think this should be...

if (q->guc->id != index)
	continue;

This way we only call guc_exec_queue_start once per queue parallel exec
queue. Also I think we need to add the same check to xe_guc_submit_stop.

Matt

> +
>  		guc_exec_queue_start(q);
> +	}
>  	mutex_unlock(&guc->submission_state.lock);
>  
>  	wake_up_all(&guc->ct.wq);
> -- 
> 2.46.0
>