From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753128AbcHNOBs (ORCPT ); Sun, 14 Aug 2016 10:01:48 -0400 Received: from mail.kernel.org ([198.145.29.136]:39304 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752258AbcHNOBr (ORCPT ); Sun, 14 Aug 2016 10:01:47 -0400 Date: Sun, 14 Aug 2016 23:01:35 +0900 From: Masami Hiramatsu To: Daniel Vetter , Jani Nikula , David Airlie Cc: linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [lockdep] drm/i915: possible circular locking dependency in i915 driver init Message-Id: <20160814230135.f647298f01687d84cc210ee5@kernel.org> X-Mailer: Sylpheed 3.5.0 (GTK+ 2.24.30; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, I've found a suspicious circular locking dependency in i915 by lockdep. It seems main driver initialization thread and sub fbdev configuration thread take locks in different order implicitly. Please check it. The lockdep report is here. [ 4.254984] ====================================================== [ 4.254984] [ INFO: possible circular locking dependency detected ] [ 4.254985] 4.8.0-rc1+ #8 Not tainted [ 4.254985] ------------------------------------------------------- [ 4.254986] kworker/u16:1/72 is trying to acquire lock: [ 4.255001] (&dev->mode_config.mutex){+.+.+.}, at: [] drm_modeset_lock_all+0x40/0x130 [drm] [ 4.255001] but task is already holding lock: [ 4.255005] ((fb_notifier_list).rwsem){++++.+}, at: [] __blocking_notifier_call_chain+0x35/0x70 [ 4.255005] which lock already depends on the new lock. [ 4.255005] the existing dependency chain (in reverse order) is: [ 4.255006] -> #1 ((fb_notifier_list).rwsem){++++.+}: [ 4.255009] [] lock_acquire+0x100/0x1f0 [ 4.255011] [] down_write+0x49/0x80 [ 4.255013] [] blocking_notifier_chain_register+0x21/0xb0 [ 4.255015] [] fb_register_client+0x18/0x20 [ 4.255016] [] backlight_device_register+0x12e/0x250 [ 4.255046] [] intel_backlight_device_register+0xa2/0x160 [i915] [ 4.255070] [] intel_connector_register+0xe/0x10 [i915] [ 4.255093] [] intel_dp_connector_register+0x1b/0x80 [i915] [ 4.255102] [] drm_connector_register+0x4a/0x80 [drm] [ 4.255110] [] drm_modeset_register_all+0x1c6/0x260 [drm] [ 4.255116] [] drm_dev_register+0xc2/0xd0 [drm] [ 4.255135] [] i915_driver_load+0x771/0x1460 [i915] [ 4.255153] [] i915_pci_probe+0x4f/0x70 [i915] [ 4.255155] [] local_pci_probe+0x45/0xa0 [ 4.255157] [] pci_device_probe+0xe1/0x130 [ 4.255159] [] driver_probe_device+0x224/0x430 [ 4.255160] [] __driver_attach+0xe3/0xf0 [ 4.255160] [] bus_for_each_dev+0x66/0xa0 [ 4.255161] [] driver_attach+0x1e/0x20 [ 4.255162] [] bus_add_driver+0x200/0x270 [ 4.255164] [] driver_register+0x60/0xe0 [ 4.255165] [] __pci_register_driver+0x60/0x70 [ 4.255182] [] i915_init+0x5b/0x62 [i915] [ 4.255183] [] do_one_initcall+0x3d/0x160 [ 4.255186] [] do_init_module+0x5f/0x1f8 [ 4.255187] [] load_module+0x246c/0x2bd0 [ 4.255188] [] SYSC_finit_module+0xbc/0xf0 [ 4.255190] [] SyS_finit_module+0xe/0x10 [ 4.255191] [] entry_SYSCALL_64_fastpath+0x23/0xc1 [ 4.255192] -> #0 (&dev->mode_config.mutex){+.+.+.}: [ 4.255194] [] __lock_acquire+0x125c/0x14b0 [ 4.255195] [] lock_acquire+0x100/0x1f0 [ 4.255197] [] mutex_lock_nested+0x69/0x3b0 [ 4.255206] [] drm_modeset_lock_all+0x40/0x130 [drm] [ 4.255212] [] drm_fb_helper_restore_fbdev_mode_unlocked+0x2b/0x80 [drm_kms_helper] [ 4.255217] [] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper] [ 4.255240] [] intel_fbdev_set_par+0x1a/0x60 [i915] [ 4.255242] [] fbcon_init+0x57f/0x600 [ 4.255244] [] visual_init+0xd6/0x130 [ 4.255245] [] do_bind_con_driver+0x1c1/0x3a0 [ 4.255246] [] do_take_over_console+0x116/0x180 [ 4.255247] [] do_fbcon_takeover+0x57/0xb0 [ 4.255249] [] fbcon_event_notify+0x658/0x750 [ 4.255250] [] notifier_call_chain+0x4a/0x70 [ 4.255251] [] __blocking_notifier_call_chain+0x4d/0x70 [ 4.255253] [] blocking_notifier_call_chain+0x16/0x20 [ 4.255254] [] fb_notifier_call_chain+0x1b/0x20 [ 4.255255] [] register_framebuffer+0x251/0x330 [ 4.255259] [] drm_fb_helper_initial_config+0x25f/0x3f0 [drm_kms_helper] [ 4.255282] [] intel_fbdev_initial_config+0x18/0x30 [i915] [ 4.255283] [] async_run_entry_fn+0x37/0x150 [ 4.255284] [] process_one_work+0x1e8/0x710 [ 4.255285] [] worker_thread+0x4b/0x4f0 [ 4.255286] [] kthread+0xef/0x110 [ 4.255287] [] ret_from_fork+0x1f/0x40 [ 4.255287] other info that might help us debug this: [ 4.255288] Possible unsafe locking scenario: [ 4.255288] CPU0 CPU1 [ 4.255288] ---- ---- [ 4.255289] lock((fb_notifier_list).rwsem); [ 4.255290] lock(&dev->mode_config.mutex); [ 4.255290] lock((fb_notifier_list).rwsem); [ 4.255291] lock(&dev->mode_config.mutex); [ 4.255291] *** DEADLOCK *** And i915 related kconfigs are here: ---- CONFIG_DRM_I915=m CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT=y CONFIG_DRM_I915_USERPTR=y CONFIG_DRM_I915_GVT=y # CONFIG_DRM_I915_WERROR is not set # CONFIG_DRM_I915_DEBUG is not set ---- I've hit this on my DELL XPS15 which has skylake CPU/GPU. Thanks, -- Masami Hiramatsu