drm/i915: Defer application of request banning to submission

As we currently do not check on submission whether the context is banned
in a timely manner it is possible for some requests to escape
cancellation after their parent context is banned. By moving the ban
into the request submission under the engine->timeline.lock, we
serialise it with the reset and setting of the context ban.

References: eb8d0f5a ("drm/i915: Remove GPU reset dependence on struct_mutex")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190213182737.12695-1-chris@chris-wilson.co.ukReviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

drivers/gpu/drm/i915/i915_request.c

@@ -366,6 +366,9 @@ void __i915_request_submit(struct i915_request *request)
 	GEM_BUG_ON(!irqs_disabled());
 	lockdep_assert_held(&engine->timeline.lock);
 
+	if (i915_gem_context_is_banned(request->gem_context))
+		i915_request_skip(request, -EIO);
+
 	GEM_BUG_ON(request->global_seqno);
 
 	seqno = next_global_seqno(&engine->timeline);

drivers/gpu/drm/i915/i915_reset.c

@@ -22,24 +22,15 @@ static void engine_skip_context(struct i915_request *rq)
 {
 	struct intel_engine_cs *engine = rq->engine;
 	struct i915_gem_context *hung_ctx = rq->gem_context;
-	struct i915_timeline *timeline = rq->timeline;
 
 	lockdep_assert_held(&engine->timeline.lock);
-	GEM_BUG_ON(timeline == &engine->timeline);
 
-	spin_lock(&timeline->lock);
+	if (!i915_request_is_active(rq))
+		return;
 
-	if (i915_request_is_active(rq)) {
-		list_for_each_entry_continue(rq,
-					     &engine->timeline.requests, link)
+	list_for_each_entry_continue(rq, &engine->timeline.requests, link)
 		if (rq->gem_context == hung_ctx)
 			i915_request_skip(rq, -EIO);
-	}
-
-	list_for_each_entry(rq, &timeline->requests, link)
-		i915_request_skip(rq, -EIO);
-
-	spin_unlock(&timeline->lock);
 }
 
 static void client_mark_guilty(struct drm_i915_file_private *file_priv,