Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752085AbaBIJs6 (ORCPT ); Sun, 9 Feb 2014 04:48:58 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51094 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751467AbaBIJsx (ORCPT ); Sun, 9 Feb 2014 04:48:53 -0500 Message-ID: <52F74EF8.9050407@redhat.com> Date: Sun, 09 Feb 2014 10:48:40 +0100 From: Maurizio Lombardi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: rjw@rjwysocki.net CC: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, cpufreq@vger.kernel.org, viresh.kumar@linaro.org, dirk.j.brandewie@intel.com, linux-pm@vger.kernel.org, linux-pm@vger.kernel.org Subject: [PATCH] intel_pstate: fix race condition in intel_pstate_init() Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is a race condition in the intel pstate driver initialization: the cpufreq_register_driver() function creates a timer that makes use of the energy_divisor variable (intel_pstate_timer_func), the problem is that energy_divisor is initialized *after* the call to cpufreq_register_driver(). This patch fixes the bug by initializing energy_divisor before the call to cpufreq_register_driver(). [ 2.351047] Intel pstate controlling: cpu 2 [ 2.355271] divide error: 0000 [#1] SMP [ 2.359222] Modules linked in: [ 2.362291] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.14.0-rc1-linux-mainline+ #7 [ 2.369933] Hardware name: wortmann To be filled by O.E.M./P8B-M Series, BIOS 6103 12/06/2012 [ 2.378441] task: ffff880223948000 ti: ffff880223944000 task.ti: ffff880223944000 [ 2.385912] RIP: 0010:[] [] intel_pstate_timer_func+0x2b7/0x430 [ 2.395060] RSP: 0000:ffff880226e03d58 EFLAGS: 00010246 [ 2.400363] RAX: 0000000006130063 RBX: ffff88022191b800 RCX: 0000000000000199 [ 2.407486] RDX: 0000000000000000 RSI: 0000000000002000 RDI: 0000000000000199 [ 2.414608] RBP: ffff880226e03dd8 R08: ffff88022191b850 R09: ffff880223948cc8 [ 2.421731] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002 [ 2.428854] R13: 0000000006130063 R14: 0000003b3a91a54e R15: ffff880226e03da4 [ 2.435984] FS: 0000000000000000(0000) GS:ffff880226e00000(0000) knlGS:0000000000000000 [ 2.444060] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 2.449794] CR2: ffff88022ffff000 CR3: 0000000001a0e000 CR4: 00000000000407f0 [ 2.456917] Stack: [ 2.458927] ffff880226e03dd8 0000000000000246 0000000000000000 ffffffff8108a0c0 [ 2.466380] 0000000000000000 ffffffff82dc18d0 ffff880226e03d98 0000000000000246 [ 2.473832] 0000000026e03da8 0000000026e03e08 0000000000000038 ffff88022191b848 [ 2.481281] Call Trace: [ 2.483725] [ 2.485651] [] ? cascade+0xb0/0xb0 [ 2.490912] [] ? intel_pstate_platform_pwr_mgmt_exists+0x1e0/0x1e0 [ 2.498736] [] call_timer_fn+0x98/0x260 [ 2.504218] [] ? cascade+0xb0/0xb0 [ 2.509263] [] ? _raw_spin_unlock_irq+0x30/0x50 [ 2.515439] [] run_timer_softirq+0x298/0x310 [ 2.521351] [] ? rcu_irq_exit+0x8f/0xe0 [ 2.526833] [] ? retint_restore_args+0x13/0x13 [ 2.532919] [] ? intel_pstate_platform_pwr_mgmt_exists+0x1e0/0x1e0 [ 2.540741] [] __do_softirq+0x144/0x4f0 [ 2.546217] [] irq_exit+0x14d/0x180 [ 2.551346] [] smp_apic_timer_interrupt+0x4a/0x60 [ 2.557688] [] apic_timer_interrupt+0x72/0x80 [ 2.563685] [ 2.565608] [] ? mark_held_locks+0x90/0x150 [ 2.571639] [] ? vprintk_emit+0x1c0/0x610 [ 2.577299] [] ? _raw_spin_unlock_irqrestore+0x40/0x80 [ 2.584083] [] printk+0x77/0x79 [ 2.588873] [] ? core_get_turbo_pstate+0x3c/0x60 [ 2.595139] [] intel_pstate_init_cpu+0x395/0x3a0 [ 2.601404] [] intel_pstate_cpu_init+0x1b/0x100 [ 2.607580] [] __cpufreq_add_dev+0x213/0x780 [ 2.613491] [] ? klist_next+0x8e/0x120 [ 2.618887] [] cpufreq_add_dev+0x10/0x20 [ 2.624451] [] subsys_interface_register+0xb1/0xe0 [ 2.630880] [] ? trace_hardirqs_on+0xd/0x10 [ 2.636711] [] cpufreq_register_driver+0xfe/0x2a0 [ 2.643055] [] intel_pstate_init+0x14a/0x310 [ 2.648972] [] ? mutex_unlock+0xe/0x10 [ 2.654361] [] ? intel_pstate_setup+0x2e/0x2e [ 2.660357] [] do_one_initcall+0xda/0x180 [ 2.666008] [] ? kernel_init_freeable+0x31a/0x31a [ 2.672357] [] do_basic_setup+0x9d/0xc0 [ 2.677833] [] ? kernel_init_freeable+0x31a/0x31a [ 2.684176] [] kernel_init_freeable+0x297/0x31a [ 2.690345] [] ? kernel_init+0xe/0xf0 [ 2.695648] [] ? trace_hardirqs_on_caller+0x105/0x1d0 [ 2.702339] [] ? rest_init+0x170/0x170 [ 2.707734] [] kernel_init+0xe/0xf0 [ 2.712866] [] ret_from_fork+0x7c/0xb0 [ 2.718262] [] ? rest_init+0x170/0x170 [ 2.723651] Code: c8 00 00 00 48 89 df 01 d6 e8 b6 f1 ff ff eb 0e 0f 1f 40 00 29 d6 48 89 df e8 a6 f1 ff ff 4b 8d 04 a4 31 d2 4c 8d 04 c3 4c 89 e8 <48> f7 35 fa 8d 9b 01 45 8b b8 40 01 00 00 41 89 c1 49 8b 80 28 [ 2.743596] RIP [] intel_pstate_timer_func+0x2b7/0x430 [ 2.750390] RSP [ 2.751934] tsc: Refined TSC clocksource calibration: 3092.975 MHz [ 2.760048] divide error: 0000 [#2] [ 2.760064] ---[ end trace b87c91b37801378a ]--- [ 2.761931] Kernel panic - not syncing: Fatal exception in interrupt Signed-off-by: Maurizio Lombardi --- drivers/cpufreq/intel_pstate.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 79606f4..bc04e73 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -956,13 +956,13 @@ static int __init intel_pstate_init(void) if (!all_cpu_data) return -ENOMEM; + rdmsrl(MSR_RAPL_POWER_UNIT, units); + energy_divisor = 1 << ((units >> 8) & 0x1f); /* bits{12:8} */ + rc = cpufreq_register_driver(&intel_pstate_driver); if (rc) goto out; - rdmsrl(MSR_RAPL_POWER_UNIT, units); - energy_divisor = 1 << ((units >> 8) & 0x1f); /* bits{12:8} */ - intel_pstate_debug_expose_params(); intel_pstate_sysfs_expose_params(); -- Maurizio Lombardi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/