drm/i915/gem: Serialise object before changing cache-level

Wait for the object to be idle before changing its cache-level and
unbinding. This was dropped as supposedly superfluous from commit
8b1c78e06e61 ("drm/i915: Avoid calling i915_gem_object_unbind holding
object lock"), but it turns out to prevent some cache dirt escaping.
Smells like papering over a race...

Closes: https://gitlab.freedesktop.org/drm/intel/issues/820
Fixes: 8b1c78e06e61 ("drm/i915: Avoid calling i915_gem_object_unbind holding object lock")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi.shyti@intel.com>
Acked-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191213223140.1830738-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_domain.c b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
index 88ab7e71f36c05e7ed6e3aac961886feee2c14f0..65f1851e2863120b8cd606cff2113eff85bc9559 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_domain.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
@@ -190,6 +190,13 @@ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
        if (obj->cache_level == cache_level)
                return 0;
 
+       ret = i915_gem_object_wait(obj,
+                                  I915_WAIT_INTERRUPTIBLE |
+                                  I915_WAIT_ALL,
+                                  MAX_SCHEDULE_TIMEOUT);
+       if (ret)
+               return ret;
+
        ret = i915_gem_object_lock_interruptible(obj);
        if (ret)
                return ret;