[Intel-gfx] [PATCH] drm/i915/blt: Remove recursive vma->lock

[Chris Wilson]

As we have already plugged the w->dma into the reservation_object, and
have set ourselves up to automatically signal the request and w->dma on
completion, we do not need to export the rq->fence directly and just use
the w->dma fence.

This avoids having to take the reservation_lock inside the worker which
cross-release lockdep would complain about. :)

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld at intel.com>
---
Patch based on the i915_active overhaul, but on the face of it should be
safe without. But let's pretend it does need the overhaul as this is one
of the motivations :)
-Chris
---
 drivers/gpu/drm/i915/gem/i915_gem_client_blt.c        | 10 ++++++----
 .../gpu/drm/i915/gem/selftests/i915_gem_client_blt.c  | 11 -----------
 2 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c b/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
index f253ec5765ad..83b5c5d13b93 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
@@ -193,10 +193,12 @@ static void clear_pages_worker(struct work_struct *work)
 			goto out_request;
 	}
 
-	/* XXX: more feverish nightmares await */
-	i915_vma_lock(vma);
-	err = i915_vma_move_to_active(vma, rq, EXEC_OBJECT_WRITE);
-	i915_vma_unlock(vma);
+	/*
+	 * w->dma is already exported via (vma|obj)->resv we need only
+	 * keep track of the GPU activity within this vma/request, and
+	 * propagate the signal from the request to w->dma.
+	 */
+	err = i915_active_ref(&vma->active, rq->fence.context, &rq->fence);
 	if (err)
 		goto out_request;
 
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_client_blt.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_client_blt.c
index f3a5eb807c1c..855481252bda 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_client_blt.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_client_blt.c
@@ -63,17 +63,6 @@ static int igt_client_fill(void *arg)
 		if (err)
 			goto err_unpin;
 
-		/*
-		 * XXX: For now do the wait without the object resv lock to
-		 * ensure we don't deadlock.
-		 */
-		err = i915_gem_object_wait(obj,
-					   I915_WAIT_INTERRUPTIBLE |
-					   I915_WAIT_ALL,
-					   MAX_SCHEDULE_TIMEOUT);
-		if (err)
-			goto err_unpin;
-
 		i915_gem_object_lock(obj);
 		err = i915_gem_object_set_to_cpu_domain(obj, false);
 		i915_gem_object_unlock(obj);
-- 
2.20.1