Re: [PATCH v2] drm/xe: Make exec_queue_kill safe to call twice

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

On Wed, Aug 14, 2024 at 01:56:54PM -0700, Daniele Ceraolo Spurio wrote:
> An upcoming PXP patch will kill queues at runtime when a PXP
> invalidation event occurs, so we need exec_queue_kill to be safe to call
> multiple times.
> 
> v2: Add documentation (Matt B)
> 
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> ---
>  drivers/gpu/drm/xe/xe_exec_queue.c | 9 +++++++++
>  drivers/gpu/drm/xe/xe_vm.c         | 8 ++++++--
>  2 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
> index 971e1234b8ea..7d170d37fdbe 100644
> --- a/drivers/gpu/drm/xe/xe_exec_queue.c
> +++ b/drivers/gpu/drm/xe/xe_exec_queue.c
> @@ -770,6 +770,15 @@ void xe_exec_queue_update_run_ticks(struct xe_exec_queue *q)
>  	xef->run_ticks[q->class] += (new_ts - old_ts) * q->width;
>  }
>  
> +/**
> + * xe_exec_queue_kill - permanently stop all execution from an exec queue
> + * @q: The exec queue
> + *
> + * This function permanently stops all activity on an exec queue. If the queue
> + * is actively executing on the HW, it will be kicked off the engine; any
> + * pending jobs are discarded and all future submissions are rejected.
> + * This function is safe to call multiple times.
> + */
>  void xe_exec_queue_kill(struct xe_exec_queue *q)
>  {
>  	struct xe_exec_queue *eq = q, *next;
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 22add5167564..6dd76f77b504 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -275,6 +275,8 @@ int xe_vm_add_compute_exec_queue(struct xe_vm *vm, struct xe_exec_queue *q)
>   * xe_vm_remove_compute_exec_queue() - Remove compute exec queue from VM
>   * @vm: The VM.
>   * @q: The exec_queue
> + *
> + * Note that this function might be called multiple times on the same queue.
>   */
>  void xe_vm_remove_compute_exec_queue(struct xe_vm *vm, struct xe_exec_queue *q)
>  {
> @@ -282,8 +284,10 @@ void xe_vm_remove_compute_exec_queue(struct xe_vm *vm, struct xe_exec_queue *q)
>  		return;
>  
>  	down_write(&vm->lock);
> -	list_del(&q->lr.link);
> -	--vm->preempt.num_exec_queues;
> +	if (!list_empty(&q->lr.link)) {
> +		list_del_init(&q->lr.link);
> +		--vm->preempt.num_exec_queues;
> +	}
>  	if (q->lr.pfence) {
>  		dma_fence_enable_sw_signaling(q->lr.pfence);
>  		dma_fence_put(q->lr.pfence);
> -- 
> 2.43.0
>