drm/i915: Move GEM activity tracking into a common struct reservation_object

In preparation to support many distinct timelines, we need to expand the
activity tracking on the GEM object to handle more than just a request
per engine. We already use the struct reservation_object on the dma-buf
to handle many fence contexts, so integrating that into the GEM object
itself is the preferred solution. (For example, we can now share the same
reservation_object between every consumer/producer using this buffer and
skip the manual import/export via dma-buf.)

v2: Reimplement busy-ioctl (by walking the reservation object), postpone
the ABI change for another day. Similarly use the reservation object to
find the last_write request (if active and from i915) for choosing
display CS flips.

Caveats:

 * busy-ioctl: busy-ioctl only reports on the native fences, it will not
warn of stalls (in set-domain-ioctl, pread/pwrite etc) if the object is
being rendered to by external fences. It also will not report the same
busy state as wait-ioctl (or polling on the dma-buf) in the same
circumstances. On the plus side, it does retain reporting of which
*i915* engines are engaged with this object.

 * non-blocking atomic modesets take a step backwards as the wait for
render completion blocks the ioctl. This is fixed in a subsequent
patch to use a fence instead for awaiting on the rendering, see
"drm/i915: Restore nonblocking awaits for modesetting"

 * dynamic array manipulation for shared-fences in reservation is slower
than the previous lockless static assignment (e.g. gem_exec_lut_handle
runtime on ivb goes from 42s to 66s), mainly due to atomic operations
(maintaining the fence refcounts).

 * loss of object-level retirement callbacks, emulated by VMA retirement
tracking.

 * minor loss of object-level last activity information from debugfs,
could be replaced with per-vma information if desired

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161028125858.23563-21-chris@chris-wilson.co.uk

1 files changed, 29 insertions, 19 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index d234c28cbb9f..01a7fa513b4a 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -196,6 +196,8 @@ static void i915_gem_request_retire(struct drm_i915_gem_request *request)
 	}
 
 	i915_gem_context_put(request->ctx);
+
+	dma_fence_signal(&request->fence);
 	i915_gem_request_put(request);
 }
 
@@ -553,33 +555,41 @@ i915_gem_request_await_object(struct drm_i915_gem_request *to,
 			      struct drm_i915_gem_object *obj,
 			      bool write)
 {
-	struct i915_gem_active *active;
-	unsigned long active_mask;
-	int idx;
+	struct dma_fence *excl;
+	int ret = 0;
 
 	if (write) {
-		active_mask = i915_gem_object_get_active(obj);
-		active = obj->last_read;
+		struct dma_fence **shared;
+		unsigned int count, i;
+
+		ret = reservation_object_get_fences_rcu(obj->resv,
+							&excl, &count, &shared);
+		if (ret)
+			return ret;
+
+		for (i = 0; i < count; i++) {
+			ret = i915_gem_request_await_dma_fence(to, shared[i]);
+			if (ret)
+				break;
+
+			dma_fence_put(shared[i]);
+		}
+
+		for (; i < count; i++)
+			dma_fence_put(shared[i]);
+		kfree(shared);
 	} else {
-		active_mask = 1;
-		active = &obj->last_write;
+		excl = reservation_object_get_excl_rcu(obj->resv);
 	}
 
-	for_each_active(active_mask, idx) {
-		struct drm_i915_gem_request *request;
-		int ret;
-
-		request = i915_gem_active_peek(&active[idx],
-					       &obj->base.dev->struct_mutex);
-		if (!request)
-			continue;
+	if (excl) {
+		if (ret == 0)
+			ret = i915_gem_request_await_dma_fence(to, excl);
 
-		ret = i915_gem_request_await_request(to, request);
-		if (ret)
-			return ret;
+		dma_fence_put(excl);
 	}
 
-	return 0;
+	return ret;
 }
 
 static void i915_gem_mark_busy(const struct intel_engine_cs *engine)