Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756197AbcJ3Xco (ORCPT ); Sun, 30 Oct 2016 19:32:44 -0400 Received: from mail-oi0-f65.google.com ([209.85.218.65]:33541 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754095AbcJ3Xcn (ORCPT ); Sun, 30 Oct 2016 19:32:43 -0400 To: LKML , Thorsten Leemhuis , Alex Deucher From: Larry Finger Subject: Regression in kernel 4.9-rcX - bisected to commit a481daa88fd4 Message-ID: <3b57a593-776b-b008-a5f2-672b9343f18a@lwfinger.net> Date: Sun, 30 Oct 2016 18:32:41 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1223 Lines: 27 With the 4.9-rcX kernel, my Dell Latitude D600 laptop has a kernel panic on shutdown in routine radeon_connector_unregister(). This problem has been bisected to show that commit a481daa88fd4 ("drm/radeon: always apply pci shutdown callbacks") is at fault. In the routine that crashes, the ddc_bus member of the struct drm_connector is NULL, thus the following one-line (line-wrapped) patch fixes the problem: diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c --- a/drivers/gpu/drm/radeon/radeon_connectors.c +++ b/drivers/gpu/drm/radeon/radeon_connectors.c @@ -931,7 +931,7 @@ static void radeon_connector_unregister(struct drm_connector *connector) { struct radeon_connector *radeon_connector = to_radeon_connector(connector); - if (radeon_connector->ddc_bus->has_aux) { + if (radeon_connector->ddc_bus && radeon_connector->ddc_bus->has_aux) { drm_dp_aux_unregister(&radeon_connector->ddc_bus->aux); radeon_connector->ddc_bus->has_aux = false; } The above change will soon be submitted as a proper patch. This posting to LKML is intended to publicize the regression as soon as possible. Larry