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

[Steven Price]

On 02/07/2021 11:52, Boris Brezillon wrote:
> 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).

Actually I'm not sure it technically lockdep - have you got
CONFIG_DEBUG_ATOMIC_SLEEP set?

Steve