From 9ee82d783eef3177928a586c1df3f08d9ced72a8 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 18 May 2017 10:46:18 +0100
Subject: [PATCH] drm/i915: Reinstate reservation_object zapping for batch_pool objects
Git-commit: 9ee82d783eef3177928a586c1df3f08d9ced72a8
Patch-mainline: v4.13-rc1
References: FATE#322643 bsc#1055900

I removed the zapping of the reservation_object->fence array of shared
fences prematurely. We don't yet have the code to zap that array when
retiring the object, and so currently it remains possible to continually
grow the shared array trapping requests when reusing the batch_pool
object across many timelines.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170518094638.5469-4-chris@chris-wilson.co.uk
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/i915_gem_batch_pool.c |   19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/i915/i915_gem_batch_pool.c
+++ b/drivers/gpu/drm/i915/i915_gem_batch_pool.c
@@ -114,12 +114,27 @@ i915_gem_batch_pool_get(struct i915_gem_
 	list_for_each_entry(obj, list, batch_pool_link) {
 		/* The batches are strictly LRU ordered */
 		if (i915_gem_object_is_active(obj)) {
-			if (!reservation_object_test_signaled_rcu(obj->resv,
-								  true))
+			struct reservation_object *resv = obj->resv;
+
+			if (!reservation_object_test_signaled_rcu(resv, true))
 				break;
 
 			i915_gem_retire_requests(pool->engine->i915);
 			GEM_BUG_ON(i915_gem_object_is_active(obj));
+
+			/*
+			 * The object is now idle, clear the array of shared
+			 * fences before we add a new request. Although, we
+			 * remain on the same engine, we may be on a different
+			 * timeline and so may continually grow the array,
+			 * trapping a reference to all the old fences, rather
+			 * than replace the existing fence.
+			 */
+			if (rcu_access_pointer(resv->fence)) {
+				reservation_object_lock(resv, NULL);
+				reservation_object_add_excl_fence(resv, NULL);
+				reservation_object_unlock(resv);
+			}
 		}
 
 		GEM_BUG_ON(!reservation_object_test_signaled_rcu(obj->resv,