Quoting Matthew Auld (2019-05-21 21:42:35)
> +static void clear_pages_signal_irq_worker(struct irq_work *work)
> +{
> + struct clear_pages_work *w = container_of(work, typeof(*w), irq_work);
> +
> + dma_fence_signal(&w->dma);
> + dma_fence_put(&w->dma);
> +}
> +
> +static void clear_pages_dma_fence_cb(struct dma_fence *fence,
> + struct dma_fence_cb *cb)
> +{
> + struct clear_pages_work *w = container_of(cb, typeof(*w), cb);
if (fence->error)
dma_fence_set_error(&w->dma, fence->error);
> +
> + /*
> + * Push the signalling of the fence into yet another worker to avoid
> + * the nightmare locking around the fence spinlock.
> + */
> + irq_work_queue(&w->irq_work);
> +}
> +
> +static void clear_pages_worker(struct work_struct *work)
> +{
> + struct clear_pages_work *w = container_of(work, typeof(*w), work);
> + struct drm_i915_private *i915 = w->ce->gem_context->i915;
> + struct drm_i915_gem_object *obj = w->sleeve->obj;
> + struct i915_vma *vma = w->sleeve->vma;
> + struct i915_request *rq;
> + int err = w->dma.error;
> +
> + if (unlikely(err))
> + goto out_signal;
> +
> + if (obj->cache_dirty) {
> + obj->write_domain = 0;
> + if (i915_gem_object_has_struct_page(obj))
> + drm_clflush_sg(w->sleeve->pages);
> + obj->cache_dirty = false;
> + }
> +
> + mutex_lock(&i915->drm.struct_mutex);
> + err = i915_vma_pin(vma, 0, 0, PIN_USER);
> + if (unlikely(err))
> + goto out_unlock;
> +
> + rq = i915_request_create(w->ce);
> + if (IS_ERR(rq)) {
> + err = PTR_ERR(rq);
> + goto out_unpin;
> + }
> +
> + /* There's no way the fence has signalled */
> + if (dma_fence_add_callback(&rq->fence, &w->cb,
> + clear_pages_dma_fence_cb))
> + GEM_BUG_ON(1);
> +
> + if (w->ce->engine->emit_init_breadcrumb) {
> + err = w->ce->engine->emit_init_breadcrumb(rq);
> + if (unlikely(err))
> + goto out_request;
> + }
> +
> + err = intel_emit_vma_fill_blt(rq, vma, w->value);
> + if (unlikely(err))
> + goto out_request;
> +
> + err = i915_vma_move_to_active(vma, rq, EXEC_OBJECT_WRITE);
> +out_request:
> + if (unlikely(err)) {
> + dma_fence_set_error(&w->dma, err);
Propagation should happen via rq signaling.
> + i915_request_skip(rq, err);
> + err = 0;
> + }
So much work to be done to unravel these locks.
-Chris
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