Provide an interface by which the system administrator can decide what state
should the CPU go to when it is offlined.
To query the hotplug states, on needs to perform a read on the sysfs tunable:
/sys/devices/system/cpu/cpu<number>/available_hotplug_states
To query or set the current state for a particular CPU, one needs to
use the sysfs interface:
/sys/devices/system/cpu/cpu<number>/current_state
This patch implements the architecture independent bits of the
cpu-offline-state framework.
Architectures which want to expose the multiple offline-states to the
userspace are expected to write a driver which can register
with this framework.
Such a driver should:
- Implement the callbacks defined in the structure struct cpu_offline_driver
which can be called into by this framework when the corresponding
sysfs interfaces are read or written into.
- Ensure that the following operation puts the CPU in the same state
as it did in the absence of the driver.
echo 0 > /sys/devices/system/cpu/cpu<number>/online
This framework also serializes the writes to the "current_state"
with respect to with the writes to the "online" sysfs tunable.
Signed-off-by: Gautham R Shenoy <e...@in.ibm.com>
---
drivers/base/cpu.c | 176 ++++++++++++++++++++++++++++++++++++++++++++++++---
include/linux/cpu.h | 30 +++++++++
2 files changed, 197 insertions(+), 9 deletions(-)
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index e62a4cc..73efc55 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -20,7 +20,161 @@ EXPORT_SYMBOL(cpu_sysdev_class);
static DEFINE_PER_CPU(struct sys_device *, cpu_sys_devices);
+struct sys_device *get_cpu_sysdev(unsigned cpu)
+{
+ if (cpu < nr_cpu_ids && cpu_possible(cpu))
+ return per_cpu(cpu_sys_devices, cpu);
+ else
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(get_cpu_sysdev);
+
+
#ifdef CONFIG_HOTPLUG_CPU
+
+struct cpu_offline_driver *cpu_offline_driver;
+static DEFINE_MUTEX(cpu_offline_driver_lock);
+
+ssize_t show_available_states(struct sys_device *dev,
+ struct sysdev_attribute *attr, char *buf)
+{
+ struct cpu *cpu = container_of(dev, struct cpu, sysdev);
+ int cpu_num = cpu->sysdev.id;
+ ssize_t ret;
+
+ mutex_lock(&cpu_offline_driver_lock);
+ if (!cpu_offline_driver) {
+ ret = -EEXIST;
+ goto out_unlock;
+ }
+
+ ret = cpu_offline_driver->read_available_states(cpu_num, buf);
+
+out_unlock:
+ mutex_unlock(&cpu_offline_driver_lock);
+
+ return ret;
+
+}
+
+ssize_t show_current_state(struct sys_device *dev,
+ struct sysdev_attribute *attr, char *buf)
+{
+ struct cpu *cpu = container_of(dev, struct cpu, sysdev);
+ int cpu_num = cpu->sysdev.id;
+ ssize_t ret = 0;
+
+ mutex_lock(&cpu_offline_driver_lock);
+ if (!cpu_offline_driver) {
+ ret = -EEXIST;
+ goto out_unlock;
+ }
+
+ ret = cpu_offline_driver->read_current_state(cpu_num, buf);
+
+out_unlock:
+ mutex_unlock(&cpu_offline_driver_lock);
+
+ return ret;
+}
+
+ssize_t store_current_state(struct sys_device *dev,
+ struct sysdev_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct cpu *cpu = container_of(dev, struct cpu, sysdev);
+ int cpu_num = cpu->sysdev.id;
+ ssize_t ret = count;
+
+ mutex_lock(&cpu_offline_driver_lock);
+ if (!cpu_offline_driver) {
+ ret = -EEXIST;
+ goto out_unlock;
+ }
+
+ ret = cpu_offline_driver->write_current_state(cpu_num, buf);
+
+out_unlock:
+ mutex_unlock(&cpu_offline_driver_lock);
+
+ if (ret >= 0)
+ ret = count;
+ return ret;
+}
+
+static SYSDEV_ATTR(available_hotplug_states, 0444, show_available_states,
+ NULL);
+static SYSDEV_ATTR(current_state, 0644, show_current_state,
+ store_current_state);
+
+/* Should be called with cpu_offline_driver_lock held */
+void cpu_offline_driver_add_cpu(struct sys_device *cpu_sys_dev)
+{
+ if (!cpu_offline_driver || !cpu_sys_dev)
+ return;
+
+ sysdev_create_file(cpu_sys_dev, &attr_available_hotplug_states);
+ sysdev_create_file(cpu_sys_dev, &attr_current_state);
+}
+
+/* Should be called with cpu_offline_driver_lock held */
+void cpu_offline_driver_remove_cpu(struct sys_device *cpu_sys_dev)
+{
+ if (!cpu_offline_driver || !cpu_sys_dev)
+ return;
+
+ sysdev_remove_file(cpu_sys_dev, &attr_available_hotplug_states);
+ sysdev_remove_file(cpu_sys_dev, &attr_current_state);
+
+}
+
+int register_cpu_offline_driver(struct cpu_offline_driver *arch_cpu_driver)
+{
+ int ret = 0;
+ int cpu;
+ mutex_lock(&cpu_offline_driver_lock);
+
+ if (cpu_offline_driver != NULL) {
+ ret = -EEXIST;
+ goto out_unlock;
+ }
+
+ if (!(arch_cpu_driver->read_available_states &&
+ arch_cpu_driver->read_current_state &&
+ arch_cpu_driver->write_current_state)) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ cpu_offline_driver = arch_cpu_driver;
+
+ for_each_possible_cpu(cpu)
+ cpu_offline_driver_add_cpu(get_cpu_sysdev(cpu));
+
+out_unlock:
+ mutex_unlock(&cpu_offline_driver_lock);
+ return ret;
+}
+
+void unregister_cpu_offline_driver(struct cpu_offline_driver *arch_cpu_driver)
+{
+ int cpu;
+ mutex_lock(&cpu_offline_driver_lock);
+
+ if (!cpu_offline_driver) {
+ WARN_ON(1);
+ mutex_unlock(&cpu_offline_driver_lock);
+ return;
+ }
+
+ for_each_possible_cpu(cpu)
+ cpu_offline_driver_remove_cpu(get_cpu_sysdev(cpu));
+
+ cpu_offline_driver = NULL;
+ mutex_unlock(&cpu_offline_driver_lock);
+}
+
+
static ssize_t show_online(struct sys_device *dev, struct sysdev_attribute
*attr,
char *buf)
{
@@ -35,6 +189,7 @@ static ssize_t __ref store_online(struct sys_device *dev,
struct sysdev_attribut
struct cpu *cpu = container_of(dev, struct cpu, sysdev);
ssize_t ret;
+ mutex_lock(&cpu_offline_driver_lock);
switch (buf[0]) {
case '0':
ret = cpu_down(cpu->sysdev.id);
@@ -50,6 +205,8 @@ static ssize_t __ref store_online(struct sys_device *dev,
struct sysdev_attribut
ret = -EINVAL;
}
+ mutex_unlock(&cpu_offline_driver_lock);
+
if (ret >= 0)
ret = count;
return ret;
@@ -59,23 +216,33 @@ static SYSDEV_ATTR(online, 0644, show_online,
store_online);
static void __cpuinit register_cpu_control(struct cpu *cpu)
{
sysdev_create_file(&cpu->sysdev, &attr_online);
+ mutex_lock(&cpu_offline_driver_lock);
+ cpu_offline_driver_add_cpu(&cpu->sysdev);
+ mutex_unlock(&cpu_offline_driver_lock);
}
+
void unregister_cpu(struct cpu *cpu)
{
int logical_cpu = cpu->sysdev.id;
unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
+ mutex_lock(&cpu_offline_driver_lock);
+ cpu_offline_driver_remove_cpu(&cpu->sysdev);
+ mutex_unlock(&cpu_offline_driver_lock);
+
sysdev_remove_file(&cpu->sysdev, &attr_online);
sysdev_unregister(&cpu->sysdev);
per_cpu(cpu_sys_devices, logical_cpu) = NULL;
return;
}
+
#else /* ... !CONFIG_HOTPLUG_CPU */
static inline void register_cpu_control(struct cpu *cpu)
{
}
+
#endif /* CONFIG_HOTPLUG_CPU */
#ifdef CONFIG_KEXEC
@@ -224,15 +391,6 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
return error;
}
-struct sys_device *get_cpu_sysdev(unsigned cpu)
-{
- if (cpu < nr_cpu_ids && cpu_possible(cpu))
- return per_cpu(cpu_sys_devices, cpu);
- else
- return NULL;
-}
-EXPORT_SYMBOL_GPL(get_cpu_sysdev);
-
int __init cpu_dev_init(void)
{
int err;
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 4d668e0..7636420 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -51,6 +51,36 @@ struct notifier_block;
#ifdef CONFIG_HOTPLUG_CPU
extern int register_cpu_notifier(struct notifier_block *nb);
extern void unregister_cpu_notifier(struct notifier_block *nb);
+
+/*
+ * struct cpu_offline_driver: Callbacks for cpu-offline state framework.
+ *
+ * Defines the hooks for the architecture dependent callbacks
+ * which can be invoked when the user queries the
+ * available_hotplug_states and current_state and sets the current_state.
+ *
+ * read_available_state: Called when the user queries available_hotplug_states.
+ * @cpu: Cpu for which available_hotplug_states are being queried.
+ * @buf: Buffer in which the available hotplug states are to be populated.
+ *
+ * read_current_state: Called when the user queries current_state.
+ * @cpu: Cpu for which current_state is being queried.
+ * @buf: Buffer in which the current_state value is to be returned.
+ *
+ * write_current_state: Called when the user wants to set the current_state.
+ * @cpu: Cpu for which the current state is being set.
+ * @buf: Buffer containing the string corresponding to the current_state
+ * that needs to be set.
+ */
+struct cpu_offline_driver {
+ ssize_t (*read_available_states)(unsigned int cpu, char *buf);
+ ssize_t (*read_current_state)(unsigned int cpu, char *buf);
+ ssize_t (*write_current_state)(unsigned int cpu, const char *buf);
+};
+
+extern int register_cpu_offline_driver(struct cpu_offline_driver *driver);
+extern void unregister_cpu_offline_driver(struct cpu_offline_driver *driver);
+
#else
#ifndef MODULE
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