From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964894AbXABV5T (ORCPT ); Tue, 2 Jan 2007 16:57:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754959AbXABV5T (ORCPT ); Tue, 2 Jan 2007 16:57:19 -0500 Received: from mga07.intel.com ([143.182.124.22]:18577 "EHLO azsmga101.ch.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754921AbXABV5R (ORCPT ); Tue, 2 Jan 2007 16:57:17 -0500 X-ExtLoop1: 1 X-IronPort-AV: i="4.12,227,1165219200"; d="scan'208"; a="164538405:sNHT25188702" Date: Tue, 2 Jan 2007 13:27:58 -0800 From: Venkatesh Pallipadi To: Dave Jones , Dominik Brodowski , Andrew Morton Cc: linux-kernel , Gautham R Shenoy Subject: Re: [PATCH] cpufreq lock rewrite bugfix - Fix locking in cpufreq_get Message-ID: <20070102132758.A17649@unix-os.sc.intel.com> References: <20061229133543.C12358@unix-os.sc.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <20061229133543.C12358@unix-os.sc.intel.com>; from venkatesh.pallipadi@intel.com on Fri, Dec 29, 2006 at 01:35:43PM -0800 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Incremental bugfix to previous 3 patch patchset of cpufreq lock rewrite. There was one code path in cpufreq_get, that was using the write lock in place of read and also potential recursive lock with sysfs interface of cpuinfo_cur_freq. Signed-off-by: Venkatesh Pallipadi Index: linux-2.6.20-rc-mm/drivers/cpufreq/cpufreq.c =================================================================== --- linux-2.6.20-rc-mm.orig/drivers/cpufreq/cpufreq.c +++ linux-2.6.20-rc-mm/drivers/cpufreq/cpufreq.c @@ -101,6 +101,7 @@ EXPORT_SYMBOL_GPL(unlock_policy_rwsem_wr /* internal prototypes */ static int __cpufreq_governor(struct cpufreq_policy *policy, unsigned int event); +static unsigned int __cpufreq_get(unsigned int cpu); static void handle_update(struct work_struct *work); /** @@ -488,7 +489,7 @@ store_one(scaling_max_freq,max); static ssize_t show_cpuinfo_cur_freq (struct cpufreq_policy * policy, char *buf) { - unsigned int cur_freq = cpufreq_get(policy->cpu); + unsigned int cur_freq = __cpufreq_get(policy->cpu); if (!cur_freq) return sprintf(buf, ""); return sprintf(buf, "%u\n", cur_freq); @@ -1074,25 +1075,13 @@ unsigned int cpufreq_quick_get(unsigned EXPORT_SYMBOL(cpufreq_quick_get); -/** - * cpufreq_get - get the current CPU frequency (in kHz) - * @cpu: CPU number - * - * Get the CPU current (static) CPU frequency - */ -unsigned int cpufreq_get(unsigned int cpu) +static unsigned int __cpufreq_get(unsigned int cpu) { - struct cpufreq_policy *policy = cpufreq_cpu_get(cpu); + struct cpufreq_policy *policy = cpufreq_cpu_data[cpu]; unsigned int ret_freq = 0; - if (!policy) - return 0; - if (!cpufreq_driver->get) - goto out; - - if (unlikely(lock_policy_rwsem_write(cpu))) - goto out; + return (ret_freq); ret_freq = cpufreq_driver->get(cpu); @@ -1106,11 +1095,32 @@ unsigned int cpufreq_get(unsigned int cp } } - unlock_policy_rwsem_write(cpu); + return (ret_freq); +} + +/** + * cpufreq_get - get the current CPU frequency (in kHz) + * @cpu: CPU number + * + * Get the CPU current (static) CPU frequency + */ +unsigned int cpufreq_get(unsigned int cpu) +{ + unsigned int ret_freq = 0; + struct cpufreq_policy *policy = cpufreq_cpu_get(cpu); + + if (!policy) + goto out; + + if (unlikely(lock_policy_rwsem_read(cpu))) + goto out; + + ret_freq = __cpufreq_get(cpu); + + unlock_policy_rwsem_read(cpu); out: cpufreq_cpu_put(policy); - return (ret_freq); } EXPORT_SYMBOL(cpufreq_get);