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Commit c32b6b8e authored by Ashok Raj's avatar Ashok Raj Committed by Linus Torvalds
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[PATCH] create and destroy cpufreq sysfs entries based on cpu notifiers 



cpufreq entries in sysfs should only be populated when CPU is online state.
 When we either boot with maxcpus=x and then boot the other cpus by echoing
to sysfs online file, these entries should be created and destroyed when
CPU_DEAD is notified.  Same treatement as cache entries under sysfs.

We place the processor in the lowest frequency, so hw managed P-State
transitions can still work on the other threads to save power.

Primary goal was to just make these directories appear/disapper dynamically.

There is one in this patch i had to do, which i really dont like myself but
probably best if someone handling the cpufreq infrastructure could give
this code right treatment if this is not acceptable.  I guess its probably
good for the first cut.

- Converting lock_cpu_hotplug()/unlock_cpu_hotplug() to disable/enable preempt.
  The locking was smack in the middle of the notification path, when the
  hotplug is already holding the lock. I tried another solution to avoid this
  so avoid taking locks if we know we are from notification path. The solution
  was getting very ugly and i decided this was probably good for this iteration
  until someone who understands cpufreq could do a better job than me.

(akpm: export cpucontrol to GPL modules: drivers/cpufreq/cpufreq_stats.c now
does lock_cpu_hotplug())

Signed-off-by: default avatarAshok Raj <ashok.raj@intel.com>
Signed-off-by: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Zwane Mwaikambo <zwane@holomorphy.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent d434fca7

drivers/cpufreq/cpufreq.c

+64 −5
Original line number Original line Diff line number Diff line
@@ -4,6 +4,9 @@ 
 *  Copyright (C) 2001 Russell King

 *  Copyright (C) 2001 Russell King

 *            (C) 2002 - 2003 Dominik Brodowski <linux@brodo.de>

 *            (C) 2002 - 2003 Dominik Brodowski <linux@brodo.de>

 *

 *

 *  Oct 2005 - Ashok Raj <ashok.raj@intel.com>

 *         		Added handling for CPU hotplug

 *

 * This program is free software; you can redistribute it and/or modify

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 * published by the Free Software Foundation.
@@ -567,6 +570,9 @@ static int cpufreq_add_dev (struct sys_device * sys_dev) 
	unsigned long flags;

	unsigned long flags;

	unsigned int j;

	unsigned int j;





	if (cpu_is_offline(cpu))

		return 0;



	cpufreq_debug_disable_ratelimit();

	cpufreq_debug_disable_ratelimit();

	dprintk("adding CPU %u\n", cpu);

	dprintk("adding CPU %u\n", cpu);
@@ -762,7 +768,6 @@ static int cpufreq_remove_dev (struct sys_device * sys_dev) 
	down(&data->lock);

	down(&data->lock);

	if (cpufreq_driver->target)

	if (cpufreq_driver->target)

		__cpufreq_governor(data, CPUFREQ_GOV_STOP);

		__cpufreq_governor(data, CPUFREQ_GOV_STOP);

	cpufreq_driver->target = NULL;

	up(&data->lock);

	up(&data->lock);





	kobject_unregister(&data->kobj);

	kobject_unregister(&data->kobj);
@@ -1109,17 +1114,30 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, 
			    unsigned int relation)

			    unsigned int relation)

{

{

	int retval = -EINVAL;

	int retval = -EINVAL;

	lock_cpu_hotplug();



	/*

	 * Converted the lock_cpu_hotplug to preempt_disable()

	 * and preempt_enable(). This is a bit kludgy and relies on how cpu

	 * hotplug works. All we need is a guarantee that cpu hotplug won't make

	 * progress on any cpu. Once we do preempt_disable(), this would ensure

	 * that hotplug threads don't get onto this cpu, thereby delaying

	 * the cpu remove process.

	 *

	 * We removed the lock_cpu_hotplug since we need to call this function

	 * via cpu hotplug callbacks, which result in locking the cpu hotplug

	 * thread itself. Agree this is not very clean, cpufreq community

	 * could improve this if required. - Ashok Raj <ashok.raj@intel.com>

	 */

	preempt_disable();

	dprintk("target for CPU %u: %u kHz, relation %u\n", policy->cpu,

	dprintk("target for CPU %u: %u kHz, relation %u\n", policy->cpu,

		target_freq, relation);

		target_freq, relation);

	if (cpu_online(policy->cpu) && cpufreq_driver->target)

	if (cpu_online(policy->cpu) && cpufreq_driver->target)

		retval = cpufreq_driver->target(policy, target_freq, relation);

		retval = cpufreq_driver->target(policy, target_freq, relation);

	unlock_cpu_hotplug();

	preempt_enable();

	return retval;

	return retval;

}

}

EXPORT_SYMBOL_GPL(__cpufreq_driver_target);

EXPORT_SYMBOL_GPL(__cpufreq_driver_target);







int cpufreq_driver_target(struct cpufreq_policy *policy,

int cpufreq_driver_target(struct cpufreq_policy *policy,

			  unsigned int target_freq,

			  unsigned int target_freq,

			  unsigned int relation)

			  unsigned int relation)
@@ -1406,6 +1424,45 @@ int cpufreq_update_policy(unsigned int cpu) 
}

}

EXPORT_SYMBOL(cpufreq_update_policy);

EXPORT_SYMBOL(cpufreq_update_policy);





static int __cpuinit cpufreq_cpu_callback(struct notifier_block *nfb,

					unsigned long action, void *hcpu)

{

	unsigned int cpu = (unsigned long)hcpu;

	struct cpufreq_policy *policy;

	struct sys_device *sys_dev;



	sys_dev = get_cpu_sysdev(cpu);



	if (sys_dev) {

		switch (action) {

		case CPU_ONLINE:

			cpufreq_add_dev(sys_dev);

			break;

		case CPU_DOWN_PREPARE:

			/*

			 * We attempt to put this cpu in lowest frequency

			 * possible before going down. This will permit

			 * hardware-managed P-State to switch other related

			 * threads to min or higher speeds if possible.

			 */

			policy = cpufreq_cpu_data[cpu];

			if (policy) {

				cpufreq_driver_target(policy, policy->min,

						CPUFREQ_RELATION_H);

			}

			break;

		case CPU_DEAD:

			cpufreq_remove_dev(sys_dev);

			break;

		}

	}

	return NOTIFY_OK;

}



static struct notifier_block cpufreq_cpu_notifier =

{

    .notifier_call = cpufreq_cpu_callback,

};





/*********************************************************************

/*********************************************************************

 *               REGISTER / UNREGISTER CPUFREQ DRIVER                *

 *               REGISTER / UNREGISTER CPUFREQ DRIVER                *
@@ -1466,6 +1523,7 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data) 
	}

	}





	if (!ret) {

	if (!ret) {

		register_cpu_notifier(&cpufreq_cpu_notifier);

		dprintk("driver %s up and running\n", driver_data->name);

		dprintk("driver %s up and running\n", driver_data->name);

		cpufreq_debug_enable_ratelimit();

		cpufreq_debug_enable_ratelimit();

	}

	}
@@ -1497,6 +1555,7 @@ int cpufreq_unregister_driver(struct cpufreq_driver *driver) 
	dprintk("unregistering driver %s\n", driver->name);

	dprintk("unregistering driver %s\n", driver->name);





	sysdev_driver_unregister(&cpu_sysdev_class, &cpufreq_sysdev_driver);

	sysdev_driver_unregister(&cpu_sysdev_class, &cpufreq_sysdev_driver);

	unregister_cpu_notifier(&cpufreq_cpu_notifier);





	spin_lock_irqsave(&cpufreq_driver_lock, flags);

	spin_lock_irqsave(&cpufreq_driver_lock, flags);

	cpufreq_driver = NULL;

	cpufreq_driver = NULL;

drivers/cpufreq/cpufreq_stats.c

+38 −4
Original line number Original line Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <linux/percpu.h>

#include <linux/percpu.h>

#include <linux/kobject.h>

#include <linux/kobject.h>

#include <linux/spinlock.h>

#include <linux/spinlock.h>

#include <linux/notifier.h>

#include <asm/cputime.h>

#include <asm/cputime.h>





static spinlock_t cpufreq_stats_lock;

static spinlock_t cpufreq_stats_lock;
@@ -298,6 +299,27 @@ cpufreq_stat_notifier_trans (struct notifier_block *nb, unsigned long val, 
	return 0;

	return 0;

}

}





static int __cpuinit cpufreq_stat_cpu_callback(struct notifier_block *nfb,

					unsigned long action, void *hcpu)

{

	unsigned int cpu = (unsigned long)hcpu;



	switch (action) {

	case CPU_ONLINE:

		cpufreq_update_policy(cpu);

		break;

	case CPU_DEAD:

		cpufreq_stats_free_table(cpu);

		break;

	}

	return NOTIFY_OK;

}



static struct notifier_block cpufreq_stat_cpu_notifier =

{

	.notifier_call = cpufreq_stat_cpu_callback,

};



static struct notifier_block notifier_policy_block = {

static struct notifier_block notifier_policy_block = {

	.notifier_call = cpufreq_stat_notifier_policy

	.notifier_call = cpufreq_stat_notifier_policy

};

};
@@ -311,6 +333,7 @@ __init cpufreq_stats_init(void) 
{

{

	int ret;

	int ret;

	unsigned int cpu;

	unsigned int cpu;



	spin_lock_init(&cpufreq_stats_lock);

	spin_lock_init(&cpufreq_stats_lock);

	if ((ret = cpufreq_register_notifier(&notifier_policy_block,

	if ((ret = cpufreq_register_notifier(&notifier_policy_block,

				CPUFREQ_POLICY_NOTIFIER)))

				CPUFREQ_POLICY_NOTIFIER)))
@@ -323,20 +346,31 @@ __init cpufreq_stats_init(void) 
		return ret;

		return ret;

	}

	}





	for_each_cpu(cpu)

	register_cpu_notifier(&cpufreq_stat_cpu_notifier);

		cpufreq_update_policy(cpu);

	lock_cpu_hotplug();

	for_each_online_cpu(cpu) {

		cpufreq_stat_cpu_callback(&cpufreq_stat_cpu_notifier, CPU_ONLINE,

			(void *)(long)cpu);

	}

	unlock_cpu_hotplug();

	return 0;

	return 0;

}

}

static void

static void

__exit cpufreq_stats_exit(void)

__exit cpufreq_stats_exit(void)

{

{

	unsigned int cpu;

	unsigned int cpu;



	cpufreq_unregister_notifier(&notifier_policy_block,

	cpufreq_unregister_notifier(&notifier_policy_block,

			CPUFREQ_POLICY_NOTIFIER);

			CPUFREQ_POLICY_NOTIFIER);

	cpufreq_unregister_notifier(&notifier_trans_block,

	cpufreq_unregister_notifier(&notifier_trans_block,

			CPUFREQ_TRANSITION_NOTIFIER);

			CPUFREQ_TRANSITION_NOTIFIER);

	for_each_cpu(cpu)

	unregister_cpu_notifier(&cpufreq_stat_cpu_notifier);

		cpufreq_stats_free_table(cpu);

	lock_cpu_hotplug();

	for_each_online_cpu(cpu) {

		cpufreq_stat_cpu_callback(&cpufreq_stat_cpu_notifier, CPU_DEAD,

			(void *)(long)cpu);

	}

	unlock_cpu_hotplug();

}

}





MODULE_AUTHOR ("Zou Nan hai <nanhai.zou@intel.com>");

MODULE_AUTHOR ("Zou Nan hai <nanhai.zou@intel.com>");

kernel/cpu.c

+1 −0
Original line number Original line Diff line number Diff line
@@ -17,6 +17,7 @@ 




/* This protects CPUs going up and down... */

/* This protects CPUs going up and down... */

DECLARE_MUTEX(cpucontrol);

DECLARE_MUTEX(cpucontrol);

EXPORT_SYMBOL_GPL(cpucontrol);





static struct notifier_block *cpu_chain;

static struct notifier_block *cpu_chain;