Re: [PATCH v2 4/7] drm/panfrost: Add the ability to create submit queues

[Steven Price <steven.price@arm.com>]

On 01/07/2021 10:12, Boris Brezillon wrote:
> Needed to keep VkQueues isolated from each other.

One more comment I noticed when I tried this out:

[...]
> +struct panfrost_submitqueue *
> +panfrost_submitqueue_create(struct panfrost_file_priv *ctx,
> +			    enum panfrost_submitqueue_priority priority,
> +			    u32 flags)
> +{
> +	struct panfrost_submitqueue *queue;
> +	enum drm_sched_priority sched_prio;
> +	int ret, i;
> +
> +	if (flags || priority >= PANFROST_SUBMITQUEUE_PRIORITY_COUNT)
> +		return ERR_PTR(-EINVAL);
> +
> +	queue = kzalloc(sizeof(*queue), GFP_KERNEL);
> +	if (!queue)
> +		return ERR_PTR(-ENOMEM);
> +
> +	queue->pfdev = ctx->pfdev;
> +	sched_prio = to_sched_prio(priority);
> +	for (i = 0; i < NUM_JOB_SLOTS; i++) {
> +		struct drm_gpu_scheduler *sched;
> +
> +		sched = panfrost_job_get_sched(ctx->pfdev, i);
> +		ret = drm_sched_entity_init(&queue->sched_entity[i],
> +					    sched_prio, &sched, 1, NULL);
> +		if (ret)
> +			break;
> +	}
> +
> +	if (ret) {
> +		for (i--; i >= 0; i--)
> +			drm_sched_entity_destroy(&queue->sched_entity[i]);
> +
> +		return ERR_PTR(ret);
> +	}
> +
> +	kref_init(&queue->refcount);
> +	idr_lock(&ctx->queues);
> +	ret = idr_alloc(&ctx->queues, queue, 0, INT_MAX, GFP_KERNEL);

This makes lockdep complain. idr_lock() is a spinlock and GFP_KERNEL can
sleep. So either we need to bring our own mutex here or not use GFP_KERNEL.

Steve