Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752163AbaBXG6F (ORCPT ); Mon, 24 Feb 2014 01:58:05 -0500 Received: from smtp.codeaurora.org ([198.145.11.231]:56410 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751326AbaBXG6C (ORCPT ); Mon, 24 Feb 2014 01:58:02 -0500 From: Saravana Kannan To: "Rafael J. Wysocki" , Viresh Kumar Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "Saravana Kannan" Subject: [PATCH] cpufreq: Set policy to non-NULL only after all hotplug online work is done Date: Sun, 23 Feb 2014 22:57:52 -0800 Message-Id: <1393225072-3997-1-git-send-email-skannan@codeaurora.org> X-Mailer: git-send-email 1.8.2.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The existing code sets the per CPU policy to a non-NULL value before all the steps performed during the hotplug online path is done. Specifically, this is done before the policy min/max, governors, etc are initialized for the policy. This in turn means that calls to cpufreq_cpu_get() return a non-NULL policy before the policy/CPU is ready to be used. To fix this, move the update of per CPU policy to a valid value after all the initialization steps for the policy are completed. Example kernel panic without this fix: [ 512.146185] Unable to handle kernel NULL pointer dereference at virtual address 00000020 [ 512.146195] pgd = c0003000 [ 512.146213] [00000020] *pgd=80000000004003, *pmd=00000000 [ 512.146228] Internal error: Oops: 206 [#1] PREEMPT SMP ARM [ 512.146297] PC is at __cpufreq_governor+0x10/0x1ac [ 512.146312] LR is at cpufreq_update_policy+0x114/0x150 [ 512.149740] ---[ end trace f23a8defea6cd706 ]--- [ 512.149761] Kernel panic - not syncing: Fatal exception [ 513.152016] CPU0: stopping [ 513.154710] CPU: 0 PID: 7136 Comm: mpdecision Tainted: G D W 3.10.0-gd727407-00074-g979ede8 #396 [ 513.317224] [] (notifier_call_chain+0x40/0x68) from [] (__blocking_notifier_call_chain+0x40/0x58) [ 513.327809] [] (__blocking_notifier_call_chain+0x40/0x58) from [] (blocking_notifier_call_chain+0x14/0x1c) [ 513.339182] [] (blocking_notifier_call_chain+0x14/0x1c) from [] (cpufreq_set_policy+0xd4/0x2b8) [ 513.349594] [] (cpufreq_set_policy+0xd4/0x2b8) from [] (cpufreq_init_policy+0x30/0x98) [ 513.359231] [] (cpufreq_init_policy+0x30/0x98) from [] (__cpufreq_add_dev.isra.17+0x4dc/0x7a4) [ 513.369560] [] (__cpufreq_add_dev.isra.17+0x4dc/0x7a4) from [] (cpufreq_cpu_callback+0x58/0x84) [ 513.379978] [] (cpufreq_cpu_callback+0x58/0x84) from [] (notifier_call_chain+0x40/0x68) [ 513.389704] [] (notifier_call_chain+0x40/0x68) from [] (__cpu_notify+0x28/0x44) [ 513.398728] [] (__cpu_notify+0x28/0x44) from [] (_cpu_up+0xf4/0x1dc) [ 513.406797] [] (_cpu_up+0xf4/0x1dc) from [] (cpu_up+0x5c/0x78) [ 513.414357] [] (cpu_up+0x5c/0x78) from [] (store_online+0x44/0x74) [ 513.422253] [] (store_online+0x44/0x74) from [] (sysfs_write_file+0x108/0x14c) [ 513.431195] [] (sysfs_write_file+0x108/0x14c) from [] (vfs_write+0xd0/0x180) [ 513.439958] [] (vfs_write+0xd0/0x180) from [] (SyS_write+0x38/0x68) [ 513.447947] [] (SyS_write+0x38/0x68) from [] (ret_fast_syscall+0x0/0x30) In this specific case, CPU0 set's CPU1's policy->governor in cpufreq_init_policy() to NULL while CPU1 is using the policy->governor in __cpufreq_governor(). Signed-off-by: Saravana Kannan --- drivers/cpufreq/cpufreq.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index cb003a6..d5ceb43 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1109,11 +1109,6 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif, goto err_set_policy_cpu; } - write_lock_irqsave(&cpufreq_driver_lock, flags); - for_each_cpu(j, policy->cpus) - per_cpu(cpufreq_cpu_data, j) = policy; - write_unlock_irqrestore(&cpufreq_driver_lock, flags); - if (cpufreq_driver->get) { policy->cur = cpufreq_driver->get(policy->cpu); if (!policy->cur) { @@ -1207,6 +1202,11 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif, policy->user_policy.governor = policy->governor; } + write_lock_irqsave(&cpufreq_driver_lock, flags); + for_each_cpu(j, policy->cpus) + per_cpu(cpufreq_cpu_data, j) = policy; + write_unlock_irqrestore(&cpufreq_driver_lock, flags); + kobject_uevent(&policy->kobj, KOBJ_ADD); up_read(&cpufreq_rwsem); -- 1.8.2.1 The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- 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/