From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C14CC468C6 for ; Thu, 19 Jul 2018 07:45:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B86FE206B7 for ; Thu, 19 Jul 2018 07:45:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B86FE206B7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mentor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731234AbeGSI1F (ORCPT ); Thu, 19 Jul 2018 04:27:05 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:34803 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727700AbeGSI1F (ORCPT ); Thu, 19 Jul 2018 04:27:05 -0400 Received: from svr-orw-mbx-01.mgc.mentorg.com ([147.34.90.201]) by relay1.mentorg.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-SHA384:256) id 1fg3bu-0000lU-EP from Jiada_Wang@mentor.com ; Thu, 19 Jul 2018 00:44:26 -0700 Received: from [134.86.193.17] (147.34.91.1) by svr-orw-mbx-01.mgc.mentorg.com (147.34.90.201) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Thu, 19 Jul 2018 00:44:23 -0700 From: Jiada Wang Subject: potential deadlock in cpufreq-dt To: , CC: Message-ID: <9e5c2419-a3c4-45fa-75c4-dcc6d9e12d86@mentor.com> Date: Thu, 19 Jul 2018 16:44:29 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: svr-orw-mbx-04.mgc.mentorg.com (147.34.90.204) To svr-orw-mbx-01.mgc.mentorg.com (147.34.90.201) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello all After enable lockdep, by poking /sys/kernel/debug/sched_features, I triggered the following lockdep report: [ 34.410559] ====================================================== [ 34.416766] WARNING: possible circular locking dependency detected [ 34.422987] 4.14.50-03493-g65adcd3b74c9-dirty #203 Tainted: G C [ 34.450785] ------------------------------------------------------ [ 34.457001] systemd-udevd/1490 is trying to acquire lock: [ 34.462432] ( [ 34.464102] opp_table_lock [ 34.466814] ){+.+.} [ 34.468932] , at: [] dev_pm_opp_get_opp_table+0x2c/0x140 [ 34.475819] but task is already holding lock: [ 34.481689] ( [ 34.483359] subsys mutex [ 34.485914] #6 [ 34.487587] ){+.+.} [ 34.489701] , at: [] subsys_interface_register+0x68/0x118 [ 34.496677] which lock already depends on the new lock. [ 34.504890] the existing dependency chain (in reverse order) is: [ 34.512406] -> #3 [ 34.515836] ( [ 34.517505] subsys mutex [ 34.520045] #6 [ 34.521715] ){+.+.}linux-kernel@vger.kernel.org [ 34.523819] : [ 34.525412] __mutex_lock+0x94/0x840 [ 34.529543] mutex_lock_nested+0x1c/0x24 [ 34.534022] subsys_interface_register+0x68/0x118 [ 34.539284] cpufreq_register_driver+0x10c/0x1d8 [ 34.544464] dt_cpufreq_probe+0xcc/0x108 [cpufreq_dt] [ 34.550074] platform_drv_probe+0x58/0xa8 [ 34.554637] driver_probe_device+0x200/0x2b4 [ 34.559463] __driver_attach+0x7c/0xac [ 34.563768] bus_for_each_dev+0xa0/0xb8 [ 34.568169] driver_attach+0x20/0x28 [ 34.568173] bus_add_driver+0x19c/0x1d8 [ 34.568177] driver_register+0x98/0xd0 [ 34.568187] __platform_driver_register+0x48/0x50 [ 34.568198] dt_cpufreq_platdrv_init+0x18/0x1000 [cpufreq_dt] [ 34.568205] do_one_initcall+0x120/0x13c [ 34.568212] do_init_module+0x5c/0x1c8 [ 34.568215] load_module+0x20f0/0x2150 [ 34.568218] SyS_finit_module+0xd4/0xe8 [ 34.568220] el0_svc_naked+0x34/0x38 [ 34.568224] -> #2 [ 34.568225] ( [ 34.568228] cpu_hotplug_lock.rw_sem [ 34.568229] ){++++} [ 34.568230] : [ 34.568236] cpus_read_lock+0x54/0xcc [ 34.568241] static_key_enable+0x14/0x2c [ 34.568247] sched_feat_write+0xd0/0x1c4 [ 34.568252] full_proxy_write+0x6c/0xac [ 34.568257] __vfs_write+0x34/0x138 [ 34.568260] vfs_write+0xc0/0x17c [ 34.568262] SyS_write+0x60/0xb8 [ 34.568265] el0_svc_naked+0x34/0x38 [ 34.568266] -> #1 [ 34.568267] ( [ 34.568269] &sb->s_type->i_mutex_key [ 34.568271] #3 [ 34.568272] ){+.+.} [ 34.568273] : [ 34.568279] down_write+0x48/0x84 [ 34.568282] start_creating+0x7c/0xd0 [ 34.568284] debugfs_create_dir+0x14/0xbc [ 34.568289] opp_debug_register+0x68/0xa8 [ 34.568293] _add_opp_dev+0x78/0xb4 [ 34.568296] dev_pm_opp_get_opp_table+0x7c/0x140 [ 34.568300] dev_pm_opp_of_add_table+0x1e0/0x4a4 [ 34.568306] InitDVFS+0x7c/0x37c [ 34.568314] PVRSRVDeviceCreate+0x324/0x610 [ 34.568317] pvr_drm_load+0x64/0x128 [ 34.568322] pvr_probe+0x70/0xa0 [ 34.568325] platform_drv_probe+0x58/0xa8 [ 34.568328] driver_probe_device+0x200/0x2b4 [ 34.568331] __driver_attach+0x7c/0xac [ 34.568334] bus_for_each_dev+0xa0/0xb8 [ 34.568337] driver_attach+0x20/0x28 [ 34.568340] bus_add_driver+0x19c/0x1d8 [ 34.568343] driver_register+0x98/0xd0 [ 34.568346] __platform_driver_register+0x48/0x50 [ 34.568352] pvr_init+0x50/0x58 [ 34.568355] do_one_initcall+0x120/0x13c [ 34.568360] kernel_init_freeable+0x26c/0x270 [ 34.568366] kernel_init+0x10/0xfc [ 34.568369] ret_from_fork+0x10/0x18 [ 34.568370] -> #0 [ 34.568372] ( [ 34.568373] opp_table_lock [ 34.568375] ){+.+.} [ 34.568376] : [ 34.568381] lock_acquire+0x224/0x250 [ 34.568384] __mutex_lock+0x94/0x840 [ 34.568387] mutex_lock_nested+0x1c/0x24 [ 34.568391] dev_pm_opp_get_opp_table+0x2c/0x140 [ 34.568394] dev_pm_opp_set_regulators+0x30/0x190 [ 34.568400] cpufreq_init+0xe4/0x304 [cpufreq_dt] [ 34.568405] cpufreq_online+0x174/0x5d8 [ 34.568408] cpufreq_add_dev+0x60/0x78linux-kernel@vger.kernel.org [ 34.568411] subsys_interface_register+0x100/0x118 [ 34.568414] cpufreq_register_driver+0x10c/0x1d8 [ 34.568419] dt_cpufreq_probe+0xcc/0x108 [cpufreq_dt] [ 34.568422] platform_drv_probe+0x58/0xa8 [ 34.568425] driver_probe_device+0x200/0x2b4 [ 34.568428] __driver_attach+0x7c/0xac [ 34.568431] bus_for_each_dev+0xa0/0xb8 [ 34.568433] driver_attach+0x20/0x28 [ 34.568436] bus_add_driver+0x19c/0x1d8 [ 34.568439] driver_register+0x98/0xd0 [ 34.568442] __platform_driver_register+0x48/0x50 [ 34.568448] dt_cpufreq_platdrv_init+0x18/0x1000 [cpufreq_dt] [ 34.568450] do_one_initcall+0x120/0x13c [ 34.568454] do_init_module+0x5c/0x1c8 [ 34.568457] load_module+0x20f0/0x2150 [ 34.568460] SyS_finit_module+0xd4/0xe8 [ 34.568462] el0_svc_naked+0x34/0x38 [ 34.568463] other info that might help us debug this: [ 34.568465] Chain exists of: [ 34.568466] opp_table_lock [ 34.568468] --> [ 34.568469] cpu_hotplug_lock.rw_sem [ 34.568470] --> [ 34.568472] subsys mutex [ 34.568473] #6 [ 34.568474] [ 34.568476] Possible unsafe locking scenario: [ 34.568478] CPU0 CPU1 [ 34.568479] ---- ---- [ 34.568481] lock( [ 34.568482] subsys mutex [ 34.568483] #6 [ 34.568484] ); [ 34.568485] lock( [ 34.568487] cpu_hotplug_lock.rw_sem [ 34.568488] ); [ 34.568489] lock( [ 34.568490] subsys mutex [ 34.568491] #6 [ 34.568492] ); [ 34.568493] lock( [ 34.568495] opp_table_lock [ 34.568496] ); [ 34.568497] *** DEADLOCK *** [ 34.568500] 4 locks held by systemd-udevd/1490: [ 34.568501] #0: [ 34.568503] ( [ 34.568504] &dev->mutex [ 34.568506] ){....} [ 34.568510] , at: [] __driver_attach+0x58/0xac [ 34.568511] #1: [ 34.568512] ( [ 34.568513] &dev->mutex [ 34.568514] ){....} [ 34.568518] , at: [] __driver_attach+0x68/0xac [ 34.568519] #2: [ 34.568520] ( [ 34.568522] cpu_hotplug_lock.rw_sem [ 34.568523] ){++++} [ 34.568526] , at: [] cpufreq_register_driver+0xa8/0x1d8 [ 34.568527] #3: [ 34.568528] ( [ 34.568530] subsys mutex [ 34.568531] #6 [ 34.568532] ){+.+.} [ 34.568535] , at: [] subsys_interface_register+0x68/0x118 [ 34.568537] stack backtrace: [ 34.568542] CPU: 1 PID: 1490 Comm: systemd-udevd Tainted: G C 4.14.50-03493-g65adcd3b3 [ 34.568544] Hardware name: Renesas H3ULCB Kingfisher board based on r8a7795 ES2.0+ (DT) [ 34.568548] Call trace: [ 34.568552] [] dump_backtrace+0x0/0x39c [ 34.568556] [] show_stack+0x14/0x1c [ 34.568561] [] dump_stack+0xb0/0xf0 [ 34.568565] [] print_circular_bug.isra.17+0x1e4/0x2c0 [ 34.568568] [] __lock_acquire+0xd0c/0x1750 [ 34.568572] [] lock_acquire+0x224/0x250 [ 34.568575] [] __mutex_lock+0x94/0x840 [ 34.568579] [] mutex_lock_nested+0x1c/0x24 [ 34.568583] [] dev_pm_opp_get_opp_table+0x2c/0x140 [ 34.568586] [] dev_pm_opp_set_regulators+0x30/0x190 [ 34.568592] [] cpufreq_init+0xe4/0x304 [cpufreq_dt] [ 34.568595] [] cpufreq_online+0x174/0x5d8 [ 34.568599] [] cpufreq_add_dev+0x60/0x78 [ 34.568602] [] subsys_interface_register+0x100/0x118 [ 34.568605] [] cpufreq_register_driver+0x10c/0x1d8 [ 34.568610] [] dt_cpufreq_probe+0xcc/0x108 [cpufreq_dt] [ 34.568614] [] platform_drv_probe+0x58/0xa8 [ 34.568617] [] driver_probe_device+0x200/0x2b4 [ 34.568620] [] __driver_attach+0x7c/0xac [ 34.568623] [] bus_for_each_dev+0xa0/0xb8 [ 34.568626] [] driver_attach+0x20/0x28 [ 34.568629] [] bus_add_driver+0x19c/0x1d8 [ 34.568632] [] driver_register+0x98/0xd0 [ 34.568636] [] __platform_driver_register+0x48/0x50 [ 34.568641] [] dt_cpufreq_platdrv_init+0x18/0x1000 [cpufreq_dt] [ 34.568644] [] do_one_initcall+0x120/0x13c [ 34.568648] [] do_init_module+0x5c/0x1c8 [ 34.568651] [] load_module+0x20f0/0x2150 [ 34.568654] [] SyS_finit_module+0xd4/0xe8 [ 34.568656] Exception stack(0xffff00001eaf3ec0 to 0xffff00001eaf4000) [ 34.568661] 3ec0: 000000000000000f 0000ffff829aff78 0000000000000000 000000000000000f [ 34.568664] 3ee0: 0000000000000000 0000000000041a40 ffffffffffffffff ffffffffffffffff [ 34.568667] 3f00: 0000000000000111 0000000000000038 4f5e424aff524446 0000000000000001 [ 34.568670] 3f20: 0000000000000000 ffffffffffff0000 0000000000000001 0000000000000020 [ 34.568674] 3f40: 0000ffff829c0f80 0000ffff82aef440 0000000000000000 0000aaab1c5e1cf0 [ 34.568676] 3f60: 0000ffff829aff78 0000000000000000 0000000000020000 0000aaab1c5d7940 [ 34.568679] 3f80: 0000aaaae9f0c000 0000000000000000 0000000000000000 0000aaaae9ed6e50 [ 34.568682] 3fa0: 0000000000000000 0000ffffcbeec410 0000ffff829a98ac 0000ffffcbeec410 [ 34.568685] 3fc0: 0000ffff82aef464 0000000040000000 000000000000000f 0000000000000111 [ 34.568688] 3fe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 [ 34.568691] [] el0_svc_naked+0x34/0x38 the deadlock occurs between load of cpufreq-dt module and write to /sys/kernel/debug/sched_features in cpufreq-dt module, it acquires cpu_hotplug_lock.rw_sem then calls subsys_interface_register() which in turns will hold &sb->s_type->i_mutex_key. while write to sched_features, firstly acquires &sb->s_type->i_mutex_key, then hold cpu_hotplug_lock.rw_sem. IMO, driver should not try to acquire &sb->s_type->i_mutex_key while holding cpu_hotplug_lock.rw_sem. could you please have a look at this issue? Thanks, Jiada