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

[Boris Brezillon]

On Fri, 2 Jul 2021 11:08:58 +0100
Steven Price <steven.price at arm.com> wrote:

> 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.
> 

Ouch! I wonder why I don't see that (I have lockdep enabled, and the
igt tests should have exercised this path).

> Steve