From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753504AbaKHBiY (ORCPT ); Fri, 7 Nov 2014 20:38:24 -0500 Received: from v094114.home.net.pl ([79.96.170.134]:58545 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752822AbaKHBiX (ORCPT ); Fri, 7 Nov 2014 20:38:23 -0500 From: "Rafael J. Wysocki" To: Prarit Bhargava Cc: linux-kernel@vger.kernel.org, robert.schoene@tu-dresden.de, sboyd@codeaurora.org, Viresh Kumar , linux-pm@vger.kernel.org Subject: Re: [PATCH 4/5] cpufreq, policy->initialized count must be atomic Date: Sat, 08 Nov 2014 02:59:11 +0100 Message-ID: <1546924.3iEqBWAUvW@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/3.16.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1415199239-19019-5-git-send-email-prarit@redhat.com> References: <1415199239-19019-1-git-send-email-prarit@redhat.com> <1415199239-19019-5-git-send-email-prarit@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, November 05, 2014 09:53:58 AM Prarit Bhargava wrote: > The policy->initialized value can be modified from several cpus concurrently if > !CPUFREQ_HAVE_GOVERNOR_PER_POLICY. This leads to a situation where a > governor maybe switched out even though the governor->initialized is greater > than one. It must be switched to atomic_t and protected with a mutex to > make sure that future read/writes obtain the correct data. Same comments as for [3/5]. If you add a new mutex, you can avoid using atomic_t. > Cc: "Rafael J. Wysocki" > Cc: Viresh Kumar > Cc: linux-pm@vger.kernel.org > Signed-off-by: Prarit Bhargava > --- > drivers/cpufreq/cpufreq.c | 12 +++++++++--- > drivers/cpufreq/cpufreq_governor.c | 4 ++-- > include/linux/cpufreq.h | 3 ++- > 3 files changed, 13 insertions(+), 6 deletions(-) > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index e33cb15..cf11de6 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -2059,10 +2059,12 @@ static int __cpufreq_governor(struct cpufreq_policy *policy, > ret = policy->governor->governor(policy, event); > > if (!ret) { > + mutex_lock(&policy->governor->initialized_mutex); > if (event == CPUFREQ_GOV_POLICY_INIT) > - policy->governor->initialized++; > + atomic_inc(&policy->governor->initialized); > else if (event == CPUFREQ_GOV_POLICY_EXIT) > - policy->governor->initialized--; > + atomic_dec(&policy->governor->initialized); > + mutex_unlock(&policy->governor->initialized_mutex); > } else { > /* Restore original values */ > mutex_lock(&cpufreq_governor_lock); > @@ -2092,7 +2094,11 @@ int cpufreq_register_governor(struct cpufreq_governor *governor) > > mutex_lock(&cpufreq_governor_mutex); > > - governor->initialized = 0; > + mutex_init(&governor->initialized_mutex); > + mutex_lock(&governor->initialized_mutex); > + atomic_set(&governor->initialized, 0); > + mutex_unlock(&governor->initialized_mutex); > + > err = -EBUSY; > if (__find_governor(governor->name) == NULL) { > err = 0; > diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c > index 32ad9db..b1ee597 100644 > --- a/drivers/cpufreq/cpufreq_governor.c > +++ b/drivers/cpufreq/cpufreq_governor.c > @@ -315,7 +315,7 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, > latency * LATENCY_MULTIPLIER)); > > if ((cdata->governor == GOV_CONSERVATIVE) && > - (!policy->governor->initialized)) { > + (!atomic_read(&policy->governor->initialized))) { > struct cs_ops *cs_ops = dbs_data->cdata->gov_ops; > > cpufreq_register_notifier(cs_ops->notifier_block, > @@ -336,7 +336,7 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, > cpufreq_put_global_kobject(); > > if ((dbs_data->cdata->governor == GOV_CONSERVATIVE) && > - (policy->governor->initialized == 1)) { > + atomic_read(&policy->governor->initialized) == 1) { > struct cs_ops *cs_ops = dbs_data->cdata->gov_ops; > > cpufreq_unregister_notifier(cs_ops->notifier_block, > diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h > index 43909ad..73cec45 100644 > --- a/include/linux/cpufreq.h > +++ b/include/linux/cpufreq.h > @@ -431,7 +431,8 @@ static inline unsigned long cpufreq_scale(unsigned long old, u_int div, > > struct cpufreq_governor { > char name[CPUFREQ_NAME_LEN]; > - int initialized; > + struct mutex initialized_mutex; > + atomic_t initialized; > int (*governor) (struct cpufreq_policy *policy, > unsigned int event); > ssize_t (*show_setspeed) (struct cpufreq_policy *policy, > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.