drm/i915: Move stale context reaping to common i915_gem_context_create

We need to reap the stale contexts for all new contexts, be they created
by user in i915_gem_context_ioctl or from opening a new file in
i915_gem_context_open. Both paths may be called very frequently
accumulating many stale contexts before any worker has a chance to run
and free their memory.

Fixes: 1acfc104cdf8 ("drm/i915: Enable rcu-only context lookups")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170705142634.18554-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_context.c

@@ -383,6 +383,10 @@ i915_gem_create_context(struct drm_i915_private *dev_priv,
 
 	lockdep_assert_held(&dev_priv->drm.struct_mutex);
 
+	/* Reap stale contexts */
+	i915_gem_retire_requests(dev_priv);
+	contexts_free(dev_priv);
+
 	ctx = __create_hw_context(dev_priv, file_priv);
 	if (IS_ERR(ctx))
 		return ctx;
@@ -989,10 +993,6 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
 	if (ret)
 		return ret;
 
-	/* Reap stale contexts */
-	i915_gem_retire_requests(dev_priv);
-	contexts_free(dev_priv);
-
 	ctx = i915_gem_create_context(dev_priv, file_priv);
 	mutex_unlock(&dev->struct_mutex);
 	if (IS_ERR(ctx))