Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751674AbcLEJwB (ORCPT ); Mon, 5 Dec 2016 04:52:01 -0500 Received: from mail-wj0-f196.google.com ([209.85.210.196]:35297 "EHLO mail-wj0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751623AbcLEJvQ (ORCPT ); Mon, 5 Dec 2016 04:51:16 -0500 Date: Mon, 5 Dec 2016 10:51:21 +0100 From: Daniel Vetter To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: Nicolai Stange , Alex Deucher , Daniel Vetter , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH] drm/radeon: don't add files at control minor debugfs directory Message-ID: <20161205095121.q37ee3dqg7jhtkrx@phenom.ffwll.local> Mail-Followup-To: Christian =?iso-8859-1?Q?K=F6nig?= , Nicolai Stange , Alex Deucher , Daniel Vetter , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org References: <20161203144700.2307-1-nicstange@gmail.com> <20161205072709.zcoja6eak2sjgd2k@phenom.ffwll.local> <5b8f4c38-c993-90af-5417-5e2e3cc38b58@amd.com> <87pol6ahxr.fsf@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Operating-System: Linux phenom 4.8.0-1-amd64 User-Agent: NeoMutt/20161104 (1.7.1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6278 Lines: 118 On Mon, Dec 05, 2016 at 09:48:02AM +0100, Christian K?nig wrote: > Am 05.12.2016 um 09:39 schrieb Nicolai Stange: > > Christian K?nig writes: > > > > > Am 05.12.2016 um 08:27 schrieb Daniel Vetter: > > > > On Sat, Dec 03, 2016 at 03:47:00PM +0100, Nicolai Stange wrote: > > > > > Since commit 8a357d10043c ("drm: Nerf DRM_CONTROL nodes"), a > > > > > struct drm_device's ->control member is always NULL. > > > > > > > > > > In the case of CONFIG_DEBUG_FS=y, radeon_debugfs_add_files() accesses > > > > > ->control->debugfs_root though. This results in the following Oops: > > > > > > > > > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 > > > > > IP: radeon_debugfs_add_files+0x90/0x100 [radeon] > > > > > PGD 0 > > > > > Oops: 0000 [#1] SMP > > > > > [...] > > > > > Call Trace: > > > > > ? work_on_cpu+0xb0/0xb0 > > > > > radeon_fence_driver_init+0x120/0x150 [radeon] > > > > > si_init+0x122/0xd50 [radeon] > > > > > ? _raw_spin_unlock_irq+0x2c/0x40 > > > > > ? device_pm_check_callbacks+0xb3/0xc0 > > > > > radeon_device_init+0x958/0xda0 [radeon] > > > > > radeon_driver_load_kms+0x9a/0x210 [radeon] > > > > > drm_dev_register+0xa9/0xd0 [drm] > > > > > drm_get_pci_dev+0x9c/0x1e0 [drm] > > > > > radeon_pci_probe+0xb8/0xe0 [radeon] > > > > > [...] > > > > > > > > > > Fix this by omitting the drm_debugfs_create_files() call for the > > > > > control minor debugfs directory which is now non-existent anyway. > > > > > > > > > > Fixes: 8a357d10043c ("drm: Nerf DRM_CONTROL nodes") > > > > > Signed-off-by: Nicolai Stange > > > > Applied to drm-misc with Dave's irc ack, thanks for your patch. > > > If it's still worth it the patch is Reviewed-by: Christian K?nig > > > . > > > > > > On the other hand when ->control is always NULL, why do we still have > > > ->control anyway? > > Yes, I was wondering about that, too. > > > > Quoting from 8a357d10043c ("drm: Nerf DRM_CONTROL nodes"): > > > > Since I don't like dead uabi, let's remove it. But since this would be > > a really big change I think it's better to start out small by simply > > not registering anything. We can garbage-collect the dead code later > > on, once we're sure it's really not used anywhere. > > > > I'd too prefer compile time errors by purging ->control here. Daniel? > > Seconded. We're super-late for 4.10, I think that'd would need to be postponened for 4.11. Not need to wait with creating the patches (drm-misc is always open), but wee need to plug the oopses first. > > > And BTW: Please double check the other drivers as well. > > # git grep '\->control' -- drivers/gpu/ > > drivers/gpu/drm/amd/amdgpu/amdgpu_device.c: adev->ddev->control->debugfs_root, > > drivers/gpu/drm/amd/amdgpu/amdgpu_device.c: adev->ddev->control); > > drivers/gpu/drm/amd/amdgpu/amdgpu_device.c: adev->ddev->control); > > > > Oops. > > Yeah, that's what I expected as well but Daniel said it would only affect > qxl. No idea why I've missed that, I guess coffee wasn't working. > > drivers/gpu/drm/amd/amdkfd/kfd_dbgdev.c: ib_packet->control = (1 << 23) | (1 << 31) | > > drivers/gpu/drm/drm_drv.c: return &dev->control; > > > > That's drm_minor_get_slot(dev, type), but grepping for DRM_MINOR_CONTROL > > doesn't yield anything -> dead code. > > > > drivers/gpu/drm/gma500/psb_intel_sdvo.c: switch (sdvo->controlled_output) { > > drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS0; > > drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS1; > > drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= type; > > drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB0; > > drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB1; > > drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS0; > > drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS1; > > drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output = 0; > > drivers/gpu/drm/i915/intel_sdvo.c: switch (sdvo->controlled_output) { > > drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS0; > > drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS1; > > drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= type; > > drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB0; > > drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB1; > > drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS0; > > drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS1; > > drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output = 0; > > drivers/gpu/drm/msm/msm_debugfs.c: ret = late_init_minor(dev->control); > > > > Not an oops but dead code. > > > > drivers/gpu/drm/qxl/qxl_debugfs.c: qdev->ddev->control->debugfs_root, > > drivers/gpu/drm/qxl/qxl_debugfs.c: qdev->ddev->control); > > drivers/gpu/drm/qxl/qxl_debugfs.c: qdev->ddev->control); > > > > Oops. > > > > > > I'll send compile-only tested patches either tonight or tomorrow. Shall > > they cover the oopses only or the dead code as well? > > Please start with the ops, cause we certainly will get complains about that > rather fast. I sent out qxl already, and yes oops patches first pls. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch