From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757201AbbA2O0V (ORCPT ); Thu, 29 Jan 2015 09:26:21 -0500 Received: from arcturus.aphlor.org ([188.246.204.175]:38814 "EHLO arcturus.aphlor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753500AbbA2O0U (ORCPT ); Thu, 29 Jan 2015 09:26:20 -0500 Date: Thu, 29 Jan 2015 09:26:15 -0500 From: Dave Jones To: Linux Kernel Cc: dri-devel@lists.freedesktop.org Subject: 3.19rc6 lockdep warning from drm_fb Message-ID: <20150129142615.GA16535@codemonkey.org.uk> Mail-Followup-To: Dave Jones , Linux Kernel , dri-devel@lists.freedesktop.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) X-Spam-Score: -2.9 (--) X-Spam-Report: Spam report generated by SpamAssassin on "arcturus.aphlor.org" Content analysis details: (-2.9 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] X-Authenticated-User: davej@codemonkey.org.uk Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The irony here of the hung task detector triggering a locking disaster. The laptop hung completely after spewing this partial trace. [11881.000016] ====================================================== [11881.000016] [ INFO: possible circular locking dependency detected ] [11881.000016] 3.19.0-rc6+ #2 Not tainted [11881.000016] ------------------------------------------------------- [11881.000016] khungtaskd/20 is trying to acquire lock: [11881.000016] ((fb_notifier_list).rwsem){.+.+.+}, at: [] __blocking_notifier_call_chain+0x39/0x70 [11881.000016] [11881.000016] but task is already holding lock: [11881.000016] (crtc_ww_class_mutex){+.+.+.}, at: [] drm_modeset_lock+0x98/0x110 [11881.000016] [11881.000016] which lock already depends on the new lock. [11881.000016] [11881.000016] [11881.000016] the existing dependency chain (in reverse order) is: [11881.000016] -> #2 (crtc_ww_class_mutex){+.+.+.}: [11881.000016] [] lock_acquire+0xc0/0x270 [11881.000016] [] mutex_lock_nested+0x78/0x3d0 [11881.000016] [] drm_modeset_lock+0xb7/0x110 [11881.000016] [] drm_mode_getconnector+0x19a/0x4b0 [11881.000016] [] drm_ioctl+0x1df/0x690 [11881.000016] [] radeon_drm_ioctl+0x4c/0x80 [11881.000016] [] do_vfs_ioctl+0x308/0x560 [11881.000016] [] SyS_ioctl+0x81/0xa0 [11881.000016] [] system_call_fastpath+0x12/0x17 [11881.000016] -> #1 (&dev->mode_config.mutex){+.+.+.}: [11881.000016] [] lock_acquire+0xc0/0x270 [11881.000016] [] mutex_lock_nested+0x78/0x3d0 [11881.000016] [] __drm_modeset_lock_all+0x90/0x120 [11881.000016] [] drm_modeset_lock_all+0x10/0x40 [11881.000016] [] drm_fb_helper_restore_fbdev_mode_unlocked+0x21/0x80 [11881.000016] [] drm_fb_helper_set_par+0x22/0x50 [11881.000016] [] radeon_fb_helper_set_par+0x1a/0x80 [11881.000016] [] fbcon_init+0x588/0x610 [11881.000016] [] visual_init+0xbc/0x120 [11881.000016] [] do_bind_con_driver+0x17e/0x3b0 [11881.000016] [] do_take_over_console+0xb4/0x1e0 [11881.000016] [] do_fbcon_takeover+0x63/0xd0 [11881.000016] [] fbcon_event_notify+0x6dd/0x7e0 [11881.000016] [] notifier_call_chain+0x62/0x100 [11881.000016] [] __blocking_notifier_call_chain+0x51/0x70 [11881.000016] [] blocking_notifier_call_chain+0x16/0x20