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From: Saravana Kannan <skannan@codeaurora.org>
To: "Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Todd Poynor <toddpoynor@google.com>,
	"Srivatsa S . Bhat" <srivatsa@mit.edu>
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 <skannan@codeaurora.org>,
	Stephen Boyd <sboyd@codeaurora.org>
Subject: [PATCH v3 2/2] cpufreq: Simplify and fix mutual exclusion with hotplug
Date: Tue, 15 Jul 2014 15:47:53 -0700	[thread overview]
Message-ID: <1405464473-3916-3-git-send-email-skannan@codeaurora.org> (raw)
In-Reply-To: <1405464473-3916-1-git-send-email-skannan@codeaurora.org>

Since we no longer alloc and destroy/freeze policy and sysfs nodes during
hotplug and suspend, we don't need to lock sysfs with hotplug. We can
achieve the same effect by checking if policy->cpus is empty.

Hotplug mutual exclusion was only done for sysfs writes. But reads need the
same protection too.  So, this patch adds that too.

Also, cpufreq driver (un)register can race with hotplug since CPU online
state can change between adding/removing the currently online devices and
registering/unregistering for hotplug notifiers. So, fix that by
registering for hotplug notifiers first before adding devices and
unregistering from hotplug notifiers first before removing devices.

Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
---
 drivers/cpufreq/cpufreq.c | 44 ++++++++++++++++++++------------------------
 1 file changed, 20 insertions(+), 24 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index a0a2ec2..f72b2b7 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -748,17 +748,18 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
 {
 	struct cpufreq_policy *policy = to_policy(kobj);
 	struct freq_attr *fattr = to_attr(attr);
-	ssize_t ret;
+	ssize_t ret = -EINVAL;
 
 	if (!down_read_trylock(&cpufreq_rwsem))
-		return -EINVAL;
-
+		return ret;
 	down_read(&policy->rwsem);
 
-	if (fattr->show)
-		ret = fattr->show(policy, buf);
-	else
-		ret = -EIO;
+	if (!cpumask_empty(policy->cpus)) {
+		if (fattr->show)
+			ret = fattr->show(policy, buf);
+		else
+			ret = -EIO;
+	}
 
 	up_read(&policy->rwsem);
 	up_read(&cpufreq_rwsem);
@@ -773,26 +774,19 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
 	struct freq_attr *fattr = to_attr(attr);
 	ssize_t ret = -EINVAL;
 
-	get_online_cpus();
-
-	if (!cpu_online(policy->cpu))
-		goto unlock;
-
 	if (!down_read_trylock(&cpufreq_rwsem))
-		goto unlock;
-
+		return ret;
 	down_write(&policy->rwsem);
 
-	if (fattr->store)
-		ret = fattr->store(policy, buf, count);
-	else
-		ret = -EIO;
+	if (!cpumask_empty(policy->cpus)) {
+		if (fattr->store)
+			ret = fattr->store(policy, buf, count);
+		else
+			ret = -EIO;
+	}
 
 	up_write(&policy->rwsem);
-
 	up_read(&cpufreq_rwsem);
-unlock:
-	put_online_cpus();
 
 	return ret;
 }
@@ -2270,6 +2264,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
 		}
 	}
 
+	register_hotcpu_notifier(&cpufreq_cpu_notifier);
+
 	ret = subsys_interface_register(&cpufreq_interface);
 	if (ret)
 		goto err_boost_unreg;
@@ -2293,13 +2289,13 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
 		}
 	}
 
-	register_hotcpu_notifier(&cpufreq_cpu_notifier);
 	pr_debug("driver %s up and running\n", driver_data->name);
 
 	return 0;
 err_if_unreg:
 	subsys_interface_unregister(&cpufreq_interface);
 err_boost_unreg:
+	unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
 	if (cpufreq_boost_supported())
 		cpufreq_sysfs_remove_file(&boost.attr);
 err_null_driver:
@@ -2327,12 +2323,12 @@ int cpufreq_unregister_driver(struct cpufreq_driver *driver)
 
 	pr_debug("unregistering driver %s\n", driver->name);
 
+	unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
+
 	subsys_interface_unregister(&cpufreq_interface);
 	if (cpufreq_boost_supported())
 		cpufreq_sysfs_remove_file(&boost.attr);
 
-	unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
-
 	down_write(&cpufreq_rwsem);
 	write_lock_irqsave(&cpufreq_driver_lock, flags);
 
-- 
1.8.2.1

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

WARNING: multiple messages have this Message-ID
From: skannan@codeaurora.org (Saravana Kannan)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3 2/2] cpufreq: Simplify and fix mutual exclusion with hotplug
Date: Tue, 15 Jul 2014 15:47:53 -0700	[thread overview]
Message-ID: <1405464473-3916-3-git-send-email-skannan@codeaurora.org> (raw)
In-Reply-To: <1405464473-3916-1-git-send-email-skannan@codeaurora.org>

Since we no longer alloc and destroy/freeze policy and sysfs nodes during
hotplug and suspend, we don't need to lock sysfs with hotplug. We can
achieve the same effect by checking if policy->cpus is empty.

Hotplug mutual exclusion was only done for sysfs writes. But reads need the
same protection too.  So, this patch adds that too.

Also, cpufreq driver (un)register can race with hotplug since CPU online
state can change between adding/removing the currently online devices and
registering/unregistering for hotplug notifiers. So, fix that by
registering for hotplug notifiers first before adding devices and
unregistering from hotplug notifiers first before removing devices.

Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
---
 drivers/cpufreq/cpufreq.c | 44 ++++++++++++++++++++------------------------
 1 file changed, 20 insertions(+), 24 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index a0a2ec2..f72b2b7 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -748,17 +748,18 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
 {
 	struct cpufreq_policy *policy = to_policy(kobj);
 	struct freq_attr *fattr = to_attr(attr);
-	ssize_t ret;
+	ssize_t ret = -EINVAL;
 
 	if (!down_read_trylock(&cpufreq_rwsem))
-		return -EINVAL;
-
+		return ret;
 	down_read(&policy->rwsem);
 
-	if (fattr->show)
-		ret = fattr->show(policy, buf);
-	else
-		ret = -EIO;
+	if (!cpumask_empty(policy->cpus)) {
+		if (fattr->show)
+			ret = fattr->show(policy, buf);
+		else
+			ret = -EIO;
+	}
 
 	up_read(&policy->rwsem);
 	up_read(&cpufreq_rwsem);
@@ -773,26 +774,19 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
 	struct freq_attr *fattr = to_attr(attr);
 	ssize_t ret = -EINVAL;
 
-	get_online_cpus();
-
-	if (!cpu_online(policy->cpu))
-		goto unlock;
-
 	if (!down_read_trylock(&cpufreq_rwsem))
-		goto unlock;
-
+		return ret;
 	down_write(&policy->rwsem);
 
-	if (fattr->store)
-		ret = fattr->store(policy, buf, count);
-	else
-		ret = -EIO;
+	if (!cpumask_empty(policy->cpus)) {
+		if (fattr->store)
+			ret = fattr->store(policy, buf, count);
+		else
+			ret = -EIO;
+	}
 
 	up_write(&policy->rwsem);
-
 	up_read(&cpufreq_rwsem);
-unlock:
-	put_online_cpus();
 
 	return ret;
 }
@@ -2270,6 +2264,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
 		}
 	}
 
+	register_hotcpu_notifier(&cpufreq_cpu_notifier);
+
 	ret = subsys_interface_register(&cpufreq_interface);
 	if (ret)
 		goto err_boost_unreg;
@@ -2293,13 +2289,13 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
 		}
 	}
 
-	register_hotcpu_notifier(&cpufreq_cpu_notifier);
 	pr_debug("driver %s up and running\n", driver_data->name);
 
 	return 0;
 err_if_unreg:
 	subsys_interface_unregister(&cpufreq_interface);
 err_boost_unreg:
+	unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
 	if (cpufreq_boost_supported())
 		cpufreq_sysfs_remove_file(&boost.attr);
 err_null_driver:
@@ -2327,12 +2323,12 @@ int cpufreq_unregister_driver(struct cpufreq_driver *driver)
 
 	pr_debug("unregistering driver %s\n", driver->name);
 
+	unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
+
 	subsys_interface_unregister(&cpufreq_interface);
 	if (cpufreq_boost_supported())
 		cpufreq_sysfs_remove_file(&boost.attr);
 
-	unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
-
 	down_write(&cpufreq_rwsem);
 	write_lock_irqsave(&cpufreq_driver_lock, flags);
 
-- 
1.8.2.1

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

  parent reply	other threads:[~2014-07-15 22:47 UTC|newest]

Thread overview: 205+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-07-10  2:37 [PATCH] cpufreq: Don't destroy/realloc policy/sysfs on hotplug/suspend Saravana Kannan
2014-07-10  2:37 ` Saravana Kannan
2014-07-11  4:18 ` [PATCH v2] " Saravana Kannan
2014-07-11  4:18   ` Saravana Kannan
2014-07-11  6:19   ` Viresh Kumar
2014-07-11  6:19     ` Viresh Kumar
2014-07-11  6:19     ` Viresh Kumar
2014-07-11  9:59     ` skannan
2014-07-11  9:59       ` skannan at codeaurora.org
2014-07-11  9:59       ` skannan
2014-07-11 10:07       ` skannan
2014-07-11 10:07         ` skannan at codeaurora.org
2014-07-11 10:07         ` skannan
2014-07-11 10:52       ` Viresh Kumar
2014-07-11 10:52         ` Viresh Kumar
2014-07-11 10:52         ` Viresh Kumar
2014-07-12  2:44         ` Saravana Kannan
2014-07-12  2:44           ` Saravana Kannan
2014-07-12  2:44           ` Saravana Kannan
2014-07-14  6:09           ` Viresh Kumar
2014-07-14  6:09             ` Viresh Kumar
2014-07-14  6:09             ` Viresh Kumar
2014-07-14 19:08             ` Saravana Kannan
2014-07-14 19:08               ` Saravana Kannan
2014-07-14 19:08               ` Saravana Kannan
2014-07-15  4:35               ` Viresh Kumar
2014-07-15  4:35                 ` Viresh Kumar
2014-07-15  4:35                 ` Viresh Kumar
2014-07-15  5:36                 ` Saravana Kannan
2014-07-15  5:36                   ` Saravana Kannan
2014-07-15  5:36                   ` Saravana Kannan
2014-07-15  5:52                   ` Viresh Kumar
2014-07-15  5:52                     ` Viresh Kumar
2014-07-15  5:52                     ` Viresh Kumar
2014-07-15  6:58                   ` Srivatsa S. Bhat
2014-07-15  6:58                     ` Srivatsa S. Bhat
2014-07-15  6:58                     ` Srivatsa S. Bhat
2014-07-15 17:35                     ` skannan
2014-07-15 17:35                       ` skannan at codeaurora.org
2014-07-15 17:35                       ` skannan
2014-07-16  7:44                       ` Srivatsa S. Bhat
2014-07-16  7:44                         ` Srivatsa S. Bhat
2014-07-16  7:44                         ` Srivatsa S. Bhat
2014-07-16  5:44                     ` Viresh Kumar
2014-07-16  5:44                       ` Viresh Kumar
2014-07-16  5:44                       ` Viresh Kumar
2014-07-16  7:49                       ` Srivatsa S. Bhat
2014-07-16  7:49                         ` Srivatsa S. Bhat
2014-07-16  7:49                         ` Srivatsa S. Bhat
2014-07-12  3:06     ` Saravana Kannan
2014-07-12  3:06       ` Saravana Kannan
2014-07-12  3:06       ` Saravana Kannan
2014-07-14  6:13       ` Viresh Kumar
2014-07-14  6:13         ` Viresh Kumar
2014-07-14  6:13         ` Viresh Kumar
2014-07-14 19:10         ` Saravana Kannan
2014-07-14 19:10           ` Saravana Kannan
2014-07-14 19:10           ` Saravana Kannan
2014-07-11  7:43   ` Srivatsa S. Bhat
2014-07-11  7:43     ` Srivatsa S. Bhat
2014-07-11 10:02     ` skannan
2014-07-11 10:02       ` skannan at codeaurora.org
2014-07-15 22:47   ` [PATCH v3 0/2] Simplify hotplug/suspend handling Saravana Kannan
2014-07-15 22:47     ` Saravana Kannan
2014-07-15 22:47     ` [PATCH v3 1/2] cpufreq: Don't destroy/realloc policy/sysfs on hotplug/suspend Saravana Kannan
2014-07-15 22:47       ` Saravana Kannan
2014-07-16  0:28       ` Saravana Kannan
2014-07-16  0:28         ` Saravana Kannan
2014-07-16  8:30         ` Viresh Kumar
2014-07-16  8:30           ` Viresh Kumar
2014-07-16  8:30           ` Viresh Kumar
2014-07-16 19:19           ` Saravana Kannan
2014-07-16 19:19             ` Saravana Kannan
2014-07-16 19:19             ` Saravana Kannan
2014-07-16  8:24       ` Viresh Kumar
2014-07-16  8:24         ` Viresh Kumar
2014-07-16  8:24         ` Viresh Kumar
2014-07-16 11:16         ` Srivatsa S. Bhat
2014-07-16 11:16           ` Srivatsa S. Bhat
2014-07-16 11:16           ` Srivatsa S. Bhat
2014-07-16 13:13           ` Viresh Kumar
2014-07-16 13:13             ` Viresh Kumar
2014-07-16 13:13             ` Viresh Kumar
2014-07-16 18:04             ` Srivatsa S. Bhat
2014-07-16 18:04               ` Srivatsa S. Bhat
2014-07-16 18:04               ` Srivatsa S. Bhat
2014-07-16 19:56             ` Saravana Kannan
2014-07-16 19:56               ` Saravana Kannan
2014-07-16 19:56               ` Saravana Kannan
2014-07-17  5:51               ` Viresh Kumar
2014-07-17  5:51                 ` Viresh Kumar
2014-07-17  5:51                 ` Viresh Kumar
2014-07-16 19:56           ` Saravana Kannan
2014-07-16 19:56             ` Saravana Kannan
2014-07-16 19:56             ` Saravana Kannan
2014-07-17  5:35             ` Viresh Kumar
2014-07-17  5:35               ` Viresh Kumar
2014-07-17  5:35               ` Viresh Kumar
2014-07-18  3:25               ` Saravana Kannan
2014-07-18  3:25                 ` Saravana Kannan
2014-07-18  3:25                 ` Saravana Kannan
2014-07-18  4:19                 ` Viresh Kumar
2014-07-18  4:19                   ` Viresh Kumar
2014-07-18  4:19                   ` Viresh Kumar
2014-07-16 20:25         ` Saravana Kannan
2014-07-16 20:25           ` Saravana Kannan
2014-07-16 20:25           ` Saravana Kannan
2014-07-16 21:45           ` Saravana Kannan
2014-07-16 21:45             ` Saravana Kannan
2014-07-16 21:45             ` Saravana Kannan
2014-07-17  6:24           ` Viresh Kumar
2014-07-17  6:24             ` Viresh Kumar
2014-07-17  6:24             ` Viresh Kumar
2014-07-16 14:29       ` Dirk Brandewie
2014-07-16 14:29         ` Dirk Brandewie
2014-07-16 15:28         ` Viresh Kumar
2014-07-16 15:28           ` Viresh Kumar
2014-07-16 15:28           ` Viresh Kumar
2014-07-16 19:42           ` Saravana Kannan
2014-07-16 19:42             ` Saravana Kannan
2014-07-16 19:42             ` Saravana Kannan
2014-07-15 22:47     ` Saravana Kannan [this message]
2014-07-15 22:47       ` [PATCH v3 2/2] cpufreq: Simplify and fix mutual exclusion with hotplug Saravana Kannan
2014-07-16  8:48       ` Viresh Kumar
2014-07-16  8:48         ` Viresh Kumar
2014-07-16  8:48         ` Viresh Kumar
2014-07-16 19:34         ` Saravana Kannan
2014-07-16 19:34           ` Saravana Kannan
2014-07-16 19:34           ` Saravana Kannan
2014-07-25  1:07     ` [PATCH v4 0/5] Simplify hotplug/suspend handling Saravana Kannan
2014-07-25  1:07       ` Saravana Kannan
2014-07-25  1:07       ` [PATCH v4 1/5] cpufreq: Don't wait for CPU to going offline to restart governor Saravana Kannan
2014-07-25  1:07         ` Saravana Kannan
2014-07-31 20:47         ` Saravana Kannan
2014-07-31 20:47           ` Saravana Kannan
2014-07-25  1:07       ` [PATCH v4 2/5] cpufreq: Keep track of which CPU owns the kobj/sysfs nodes separately Saravana Kannan
2014-07-25  1:07         ` Saravana Kannan
2014-08-07  9:02         ` Viresh Kumar
2014-08-07  9:02           ` Viresh Kumar
2014-08-07  9:02           ` Viresh Kumar
2014-07-25  1:07       ` [PATCH v4 3/5] cpufreq: Don't destroy/realloc policy/sysfs on hotplug/suspend Saravana Kannan
2014-07-25  1:07         ` Saravana Kannan
2014-07-31 21:56         ` Rafael J. Wysocki
2014-07-31 21:56           ` Rafael J. Wysocki
2014-07-31 22:15           ` Saravana Kannan
2014-07-31 22:15             ` Saravana Kannan
2014-07-31 23:48           ` Saravana Kannan
2014-07-31 23:48             ` Saravana Kannan
2014-07-31 23:48             ` Saravana Kannan
2014-08-07 10:51           ` Viresh Kumar
2014-08-07 10:51             ` Viresh Kumar
2014-08-07 10:51             ` Viresh Kumar
2014-08-12  9:17             ` Viresh Kumar
2014-08-12  9:17               ` Viresh Kumar
2014-08-12  9:17               ` Viresh Kumar
2014-08-07 10:48         ` Viresh Kumar
2014-08-07 10:48           ` Viresh Kumar
2014-08-07 10:48           ` Viresh Kumar
2014-08-11 22:13           ` Saravana Kannan
2014-08-11 22:13             ` Saravana Kannan
2014-08-11 22:13             ` Saravana Kannan
2014-08-12  8:51             ` Viresh Kumar
2014-08-12  8:51               ` Viresh Kumar
2014-08-12  8:51               ` Viresh Kumar
2014-07-25  1:07       ` [PATCH v4 4/5] cpufreq: Properly handle physical CPU hot-add/hot-remove Saravana Kannan
2014-07-25  1:07         ` Saravana Kannan
2014-07-25  1:07         ` Saravana Kannan
2014-08-07 11:02         ` Viresh Kumar
2014-08-07 11:02           ` Viresh Kumar
2014-08-07 11:02           ` Viresh Kumar
2014-08-11 22:15           ` Saravana Kannan
2014-08-11 22:15             ` Saravana Kannan
2014-08-11 22:15             ` Saravana Kannan
2014-07-25  1:07       ` [PATCH v4 5/5] cpufreq: Delete dead code related to policy save/restore Saravana Kannan
2014-07-25  1:07         ` Saravana Kannan
2014-08-07 11:06         ` Viresh Kumar
2014-08-07 11:06           ` Viresh Kumar
2014-08-07 11:06           ` Viresh Kumar
2014-07-29  5:52       ` [PATCH v4 0/5] Simplify hotplug/suspend handling skannan
2014-07-29  5:52         ` skannan at codeaurora.org
2014-07-29  5:52         ` skannan
2014-07-30  0:29       ` Rafael J. Wysocki
2014-07-30  0:29         ` Rafael J. Wysocki
2014-07-31 20:25         ` Saravana Kannan
2014-07-31 20:25           ` Saravana Kannan
2014-08-07  6:04         ` skannan
2014-08-07  6:04           ` skannan at codeaurora.org
2014-10-16  8:53       ` Viresh Kumar
2014-10-16  8:53         ` Viresh Kumar
2014-10-16  8:53         ` Viresh Kumar
2014-10-23 21:41         ` Saravana Kannan
2014-10-23 21:41           ` Saravana Kannan
2014-10-23 21:41           ` Saravana Kannan
2014-07-16 22:02 ` [PATCH] cpufreq: Don't destroy/realloc policy/sysfs on hotplug/suspend Rafael J. Wysocki
2014-07-16 22:02   ` Rafael J. Wysocki
2014-07-16 22:35   ` Saravana Kannan
2014-07-16 22:35     ` Saravana Kannan
2014-07-24  3:02   ` Saravana Kannan
2014-07-24  3:02     ` Saravana Kannan
2014-07-24  5:04     ` Viresh Kumar
2014-07-24  5:04       ` Viresh Kumar
2014-07-24  5:04       ` Viresh Kumar
2014-07-24  9:12       ` skannan
2014-07-24  9:12         ` skannan at codeaurora.org
2014-07-24  9:12         ` skannan

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