Re: [PATCH 10/11] drm/i915: Mark the context and address space as closed

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 14/12/15 11:36, Chris Wilson wrote:
> When the user closes the context mark it and the dependent address space
> as closed. As we use an asynchronous destruct method, this has two purposes.
> First it allows us to flag the closed context and detect internal errors if
> we to create any new objects for it (as it is removed from the user's
> namespace, these should be internal bugs only). And secondly, it allows
> us to immediately reap stale vma.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/i915_drv.h         |  4 ++++
>   drivers/gpu/drm/i915/i915_gem.c         | 15 ++++++++-----
>   drivers/gpu/drm/i915/i915_gem_context.c | 39 +++++++++++++++++++++++++++++----
>   drivers/gpu/drm/i915/i915_gem_gtt.c     | 11 +++++++---
>   drivers/gpu/drm/i915/i915_gem_gtt.h     |  9 ++++++++
>   drivers/gpu/drm/i915/i915_gem_stolen.c  |  2 +-
>   6 files changed, 66 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 696469a06715..66ecd6b3df95 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -892,6 +892,8 @@ struct intel_context {
>   	} engine[I915_NUM_RINGS];
>
>   	struct list_head link;
> +
> +	bool closed:1;
>   };
>
>   enum fb_op_origin {
> @@ -2720,6 +2722,8 @@ int __must_check i915_vma_unbind(struct i915_vma *vma);
>    * _guarantee_ VMA in question is _not in use_ anywhere.
>    */
>   int __must_check __i915_vma_unbind_no_wait(struct i915_vma *vma);
> +void i915_vma_close(struct i915_vma *vma);
> +
>   int i915_gem_object_put_pages(struct drm_i915_gem_object *obj);
>   void i915_gem_release_all_mmaps(struct drm_i915_private *dev_priv);
>   void i915_gem_release_mmap(struct drm_i915_gem_object *obj);
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 7c13c27a6470..08ea0b7eda8b 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2367,12 +2367,13 @@ i915_gem_object_flush_active(struct drm_i915_gem_object *obj)
>   	return 0;
>   }
>
> -static void i915_vma_close(struct i915_vma *vma)
> +void i915_vma_close(struct i915_vma *vma)
>   {
>   	RQ_BUG_ON(vma->closed);
>   	vma->closed = true;
>
>   	list_del_init(&vma->obj_link);
> +	list_del_init(&vma->vm_link);
>   	if (!vma->active)
>   		WARN_ON(i915_vma_unbind(vma));
>   }
> @@ -2620,12 +2621,13 @@ static int __i915_vma_unbind(struct i915_vma *vma, bool wait)
>   			return ret;
>   	}
>
> -	trace_i915_vma_unbind(vma);
> -
> -	vma->vm->unbind_vma(vma);
> +	if (likely(!vma->vm->closed)) {
> +		trace_i915_vma_unbind(vma);
> +		vma->vm->unbind_vma(vma);
> +	}
>   	vma->bound = 0;
>
> -	list_del_init(&vma->vm_link);
> +	list_move_tail(&vma->vm_link, &vma->vm->unbound_list);
>   	if (vma->is_ggtt) {
>   		if (vma->ggtt_view.type == I915_GGTT_VIEW_NORMAL) {
>   			obj->map_and_fenceable = false;
> @@ -2882,7 +2884,7 @@ search_free:
>   		goto err_remove_node;
>
>   	list_move_tail(&obj->global_list, &dev_priv->mm.bound_list);
> -	list_add_tail(&vma->vm_link, &vm->inactive_list);
> +	list_move_tail(&vma->vm_link, &vm->inactive_list);
>
>   	return vma;
>
> @@ -3890,6 +3892,7 @@ void i915_gem_vma_destroy(struct i915_vma *vma)
>   	if (!list_empty(&vma->exec_list))
>   		return;
>
> +	list_del(&vma->vm_link);
>   	if (!vma->is_ggtt)
>   		i915_ppgtt_put(i915_vm_to_ppgtt(vma->vm));
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index c4a8a64cd1b2..9669547c7c2d 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -153,6 +153,7 @@ void i915_gem_context_free(struct kref *ctx_ref)
>   	struct intel_context *ctx = container_of(ctx_ref, typeof(*ctx), ref);
>
>   	trace_i915_context_free(ctx);
> +	RQ_BUG_ON(!ctx->closed);
>
>   	if (i915.enable_execlists)
>   		intel_lr_context_free(ctx);
> @@ -209,6 +210,36 @@ i915_gem_alloc_context_obj(struct drm_device *dev, size_t size)
>   	return obj;
>   }
>
> +static void i915_ppgtt_close(struct i915_address_space *vm)
> +{
> +	struct list_head *phases[] = {
> +		&vm->active_list,
> +		&vm->inactive_list,
> +		&vm->unbound_list,
> +		NULL,
> +	}, **phase;
> +
> +	RQ_BUG_ON(vm->is_ggtt);
> +	RQ_BUG_ON(vm->closed);
> +	vm->closed = true;
> +
> +	for (phase = phases; *phase; phase++) {
> +		struct i915_vma *vma, *vn;
> +
> +		list_for_each_entry_safe(vma, vn, *phase, vm_link)
> +			i915_vma_close(vma);
> +	}
> +}

Hm so VMAs get unlinked from everywhere, but then on retire goes back to 
inactive. Is it not a bit weird?

Why it is needed to unlink VMAs from everywhere when marking them as closed?

And actually on retire objects are ahead of VMAs in the req->active_list 
so the last object unreference happens before the last vma is retired, 
which is even weirder.

Am I missing something?

Regards,

Tvrtko
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