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.
Signed-off-by: Ashok Raj <[email protected]>
Signed-off-by: Venkatesh Pallipadi <[email protected]>
----------------------------------------------------------
drivers/cpufreq/cpufreq.c | 68 +++++++++++++++++++++++++++++++++++++---
drivers/cpufreq/cpufreq_stats.c | 42 ++++++++++++++++++++++--
2 files changed, 102 insertions(+), 8 deletions(-)
Index: linux-2.6.14-rc4-mm1/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-2.6.14-rc4-mm1.orig/drivers/cpufreq/cpufreq.c
+++ linux-2.6.14-rc4-mm1/drivers/cpufreq/cpufreq.c
@@ -3,6 +3,9 @@
*
* Copyright (C) 2001 Russell King
* (C) 2002 - 2003 Dominik Brodowski <[email protected]>
+ *
+ * Oct 2005 - Ashok Raj <[email protected]>
+ * 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
@@ -567,6 +570,9 @@ static int cpufreq_add_dev (struct sys_d
unsigned long flags;
unsigned int j;
+ if (cpu_is_offline(cpu))
+ return 0;
+
cpufreq_debug_disable_ratelimit();
dprintk("adding CPU %u\n", cpu);
@@ -672,7 +678,7 @@ err_out:
nomem_out:
module_put(cpufreq_driver->owner);
- module_out:
+module_out:
cpufreq_debug_enable_ratelimit();
return ret;
}
@@ -761,7 +767,6 @@ static int cpufreq_remove_dev (struct sy
down(&data->lock);
if (cpufreq_driver->target)
__cpufreq_governor(data, CPUFREQ_GOV_STOP);
- cpufreq_driver->target = NULL;
up(&data->lock);
kobject_unregister(&data->kobj);
@@ -1108,12 +1113,26 @@ int __cpufreq_driver_target(struct cpufr
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 gaurantee that cpu hotplug
+ * wont make progress on any cpu. Once we do preempt_disable(), this
+ * would ensure hotplug threads dont get on 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 <[email protected]>
+ */
+ 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);
@@ -1405,6 +1424,45 @@ int cpufreq_update_policy(unsigned int c
}
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:
+ (void) 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:
+ (void) 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 *
@@ -1465,6 +1523,7 @@ int cpufreq_register_driver(struct cpufr
}
if (!ret) {
+ register_cpu_notifier(&cpufreq_cpu_notifier);
dprintk("driver %s up and running\n", driver_data->name);
cpufreq_debug_enable_ratelimit();
}
@@ -1496,6 +1555,7 @@ int cpufreq_unregister_driver(struct cpu
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;
Index: linux-2.6.14-rc4-mm1/drivers/cpufreq/cpufreq_stats.c
===================================================================
--- linux-2.6.14-rc4-mm1.orig/drivers/cpufreq/cpufreq_stats.c
+++ linux-2.6.14-rc4-mm1/drivers/cpufreq/cpufreq_stats.c
@@ -19,6 +19,7 @@
#include <linux/percpu.h>
#include <linux/kobject.h>
#include <linux/spinlock.h>
+#include <linux/notifier.h>
#include <asm/cputime.h>
static spinlock_t cpufreq_stats_lock;
@@ -296,6 +297,27 @@ cpufreq_stat_notifier_trans (struct noti
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 = {
.notifier_call = cpufreq_stat_notifier_policy
};
@@ -309,6 +331,7 @@ __init cpufreq_stats_init(void)
{
int ret;
unsigned int cpu;
+
spin_lock_init(&cpufreq_stats_lock);
if ((ret = cpufreq_register_notifier(¬ifier_policy_block,
CPUFREQ_POLICY_NOTIFIER)))
@@ -321,20 +344,31 @@ __init cpufreq_stats_init(void)
return ret;
}
- for_each_cpu(cpu)
- cpufreq_update_policy(cpu);
+ register_cpu_notifier(&cpufreq_stat_cpu_notifier);
+ 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;
}
static void
__exit cpufreq_stats_exit(void)
{
unsigned int cpu;
+
cpufreq_unregister_notifier(¬ifier_policy_block,
CPUFREQ_POLICY_NOTIFIER);
cpufreq_unregister_notifier(¬ifier_trans_block,
CPUFREQ_TRANSITION_NOTIFIER);
- for_each_cpu(cpu)
- cpufreq_stats_free_table(cpu);
+ unregister_cpu_notifier(&cpufreq_stat_cpu_notifier);
+ 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 <[email protected]>");
--
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