[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: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Venkatesh 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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 346906a..6c6121b 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -4,6 +4,9 @@
* Copyright (C) 2001 Russell King
* (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
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
@@ -567,6 +570,9 @@
unsigned long flags;
unsigned int j;
+ if (cpu_is_offline(cpu))
+ return 0;
+
cpufreq_debug_disable_ratelimit();
dprintk("adding CPU %u\n", cpu);
@@ -673,7 +679,7 @@
nomem_out:
module_put(cpufreq_driver->owner);
- module_out:
+module_out:
cpufreq_debug_enable_ratelimit();
return ret;
}
@@ -762,7 +768,6 @@
down(&data->lock);
if (cpufreq_driver->target)
__cpufreq_governor(data, CPUFREQ_GOV_STOP);
- cpufreq_driver->target = NULL;
up(&data->lock);
kobject_unregister(&data->kobj);
@@ -1109,17 +1114,30 @@
unsigned int relation)
{
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,
target_freq, relation);
if (cpu_online(policy->cpu) && cpufreq_driver->target)
retval = cpufreq_driver->target(policy, target_freq, relation);
- unlock_cpu_hotplug();
+ preempt_enable();
return retval;
}
EXPORT_SYMBOL_GPL(__cpufreq_driver_target);
-
int cpufreq_driver_target(struct cpufreq_policy *policy,
unsigned int target_freq,
unsigned int relation)
@@ -1406,6 +1424,45 @@
}
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 *
@@ -1466,6 +1523,7 @@
}
if (!ret) {
+ register_cpu_notifier(&cpufreq_cpu_notifier);
dprintk("driver %s up and running\n", driver_data->name);
cpufreq_debug_enable_ratelimit();
}
@@ -1497,6 +1555,7 @@
dprintk("unregistering driver %s\n", driver->name);
sysdev_driver_unregister(&cpu_sysdev_class, &cpufreq_sysdev_driver);
+ unregister_cpu_notifier(&cpufreq_cpu_notifier);
spin_lock_irqsave(&cpufreq_driver_lock, flags);
cpufreq_driver = NULL;