From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752575AbaIJOMX (ORCPT ); Wed, 10 Sep 2014 10:12:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36040 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751774AbaIJOMS (ORCPT ); Wed, 10 Sep 2014 10:12:18 -0400 From: Prarit Bhargava To: linux-kernel@vger.kernel.org Cc: Prarit Bhargava , "Rafael J. Wysocki" , Viresh Kumar , linux-pm@vger.kernel.org Subject: [PATCH] cpufreq, release policy->rwsem on error Date: Wed, 10 Sep 2014 10:12:08 -0400 Message-Id: <1410358328-27303-1-git-send-email-prarit@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I have not been able to reliably reproduce the hardware failure that caused the warning. In order to reproduce this I resorted to (sorry for the cut-and-paste) diff --git a/drivers/cpufreq/pcc-cpufreq.c b/drivers/cpufreq/pcc-cpufreq.c index 728a2d8..c7724d2 100644 --- a/drivers/cpufreq/pcc-cpufreq.c +++ b/drivers/cpufreq/pcc-cpufreq.c @@ -146,6 +146,8 @@ static unsigned int pcc_get_freq(unsigned int cpu) u32 input_buffer; u32 output_buffer; + return 0; + spin_lock(&pcc_lock); pr_debug("get: get_freq for CPU %d\n", cpu); to simulate the cpufreq_driver->get() hardware failure. ---8<--- While debugging a cpufreq-related hardware failure on a system I saw the following lockdep warning: ========================= [ BUG: held lock freed! ] 3.17.0-rc4+ #1 Tainted: G E ------------------------- insmod/2247 is freeing memory ffff88006e1b1400-ffff88006e1b17ff, with a lock still held there! (&policy->rwsem){+.+...}, at: [] __cpufreq_add_dev.isra.21+0x47d/0xb80 3 locks held by insmod/2247: #0: (subsys mutex#5){+.+.+.}, at: [] subsys_interface_register+0x69/0x120 #1: (cpufreq_rwsem){.+.+.+}, at: [] __cpufreq_add_dev.isra.21+0x73/0xb80 #2: (&policy->rwsem){+.+...}, at: [] __cpufreq_add_dev.isra.21+0x47d/0xb80 stack backtrace: CPU: 0 PID: 2247 Comm: insmod Tainted: G E 3.17.0-rc4+ #1 Hardware name: HP ProLiant MicroServer Gen8, BIOS J06 08/24/2013 0000000000000000 000000008f3063c4 ffff88006f87bb30 ffffffff8171b358 ffff88006bcf3750 ffff88006f87bb68 ffffffff810e09e1 ffff88006e1b1400 ffffea0001b86c00 ffffffff8156d327 ffff880073003500 0000000000000246 Call Trace: [] dump_stack+0x4d/0x66 [] debug_check_no_locks_freed+0x171/0x180 [] ? __cpufreq_add_dev.isra.21+0x427/0xb80 [] kfree+0xab/0x2b0 [] __cpufreq_add_dev.isra.21+0x427/0xb80 [] ? _raw_spin_unlock+0x27/0x40 [] ? pcc_cpufreq_do_osc+0x17f/0x17f [pcc_cpufreq] [] cpufreq_add_dev+0xe/0x10 [] subsys_interface_register+0xc1/0x120 [] cpufreq_register_driver+0x112/0x340 [] ? kfree+0xda/0x2b0 [] ? pcc_cpufreq_do_osc+0x17f/0x17f [pcc_cpufreq] [] pcc_cpufreq_init+0x4af/0xe81 [pcc_cpufreq] [] ? pcc_cpufreq_do_osc+0x17f/0x17f [pcc_cpufreq] [] do_one_initcall+0xd4/0x210 [] ? __vunmap+0xd2/0x120 [] load_module+0x1315/0x1b70 [] ? store_uevent+0x70/0x70 [] ? copy_module_from_fd.isra.44+0x129/0x180 [] SyS_finit_module+0xa6/0xd0 [] system_call_fastpath+0x16/0x1b cpufreq: __cpufreq_add_dev: ->get() failed insmod: ERROR: could not insert module pcc-cpufreq.ko: No such device The warning occurs in the __cpufreq_add_dev() code which does down_write(&policy->rwsem); ... if (cpufreq_driver->get && !cpufreq_driver->setpolicy) { policy->cur = cpufreq_driver->get(policy->cpu); if (!policy->cur) { pr_err("%s: ->get() failed\n", __func__); goto err_get_freq; } If cpufreq_driver->get(policy->cpu) returns an error we execute the code at err_get_freq, which does not up the policy->rwsem. This causes the lockdep warning. Trivial patch to up the policy->rwsem in the error path. After the patch has been applied, and an error occurs in the cpufreq_driver->get(policy->cpu) call we will now see cpufreq: __cpufreq_add_dev: ->get() failed cpufreq: __cpufreq_add_dev: ->get() failed modprobe: ERROR: could not insert 'pcc_cpufreq': No such device Signed-off-by: Prarit Bhargava Cc: "Rafael J. Wysocki" Cc: Viresh Kumar Cc: linux-pm@vger.kernel.org --- drivers/cpufreq/cpufreq.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index d9fdedd..aadaed0 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1289,6 +1289,8 @@ err_get_freq: per_cpu(cpufreq_cpu_data, j) = NULL; write_unlock_irqrestore(&cpufreq_driver_lock, flags); + up_write(&policy->rwsem); + if (cpufreq_driver->exit) cpufreq_driver->exit(policy); err_set_policy_cpu: -- 1.7.9.3