/* CPU control.
* (C) 2001, 2002, 2003, 2004 Rusty Russell
*
* This code is licenced under the GPL.
*/
#include <linux/proc_fs.h>
#include <linux/smp.h>
#include <linux/init.h>
#include <linux/notifier.h>
#include <linux/sched.h>
#include <linux/unistd.h>
#include <linux/cpu.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/stop_machine.h>
#include <linux/mutex.h>
/* This protects CPUs going up and down... */
static DEFINE_MUTEX(cpu_add_remove_lock);
static DEFINE_MUTEX(cpu_bitmask_lock);
static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain);
/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
* Should always be manipulated under cpu_add_remove_lock
*/
static int cpu_hotplug_disabled;
#ifdef CONFIG_HOTPLUG_CPU
/* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
static struct task_struct *recursive;
static int recursive_depth;
void lock_cpu_hotplug(void)
{
struct task_struct *tsk = current;
if (tsk == recursive) {
static int warnings = 10;
if (warnings) {
printk(KERN_ERR "Lukewarm IQ detected in hotplug locking\n");
WARN_ON(1);
warnings--;
}
recursive_depth++;
return;
}
mutex_lock(&cpu_bitmask_lock);
recursive = tsk;
}
EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
void unlock_cpu_hotplug(void)
{
WARN_ON(recursive != current);
if (recursive_depth) {
recursive_depth--;
return;
}
mutex_unlock(&cpu_bitmask_lock);
recursive = NULL;
}
EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
#endif /* CONFIG_HOTPLUG_CPU */
/* Need to know about CPUs going up/down? */
int __cpuinit register_cpu_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_register(&cpu_chain, nb);
}
#ifdef CONFIG_HOTPLUG_CPU
EXPORT_SYMBOL(register_cpu_notifier);
void unregister_cpu_notifier(struct notifier_block *nb)
{
blocking_notifier_chain_unregister(&cpu_chain, nb);
}
EXPORT_SYMBOL(unregister_cpu_notifier);
static inline void check_for_tasks(int cpu)
{
struct task_struct *p;
write_lock_irq(&tasklist_lock);
for_each_process(p) {
if (task_cpu(p) == cpu &&
(!cputime_eq(p->utime, cputime_zero) ||
!cputime_eq(p->stime, cputime_zero)))
printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
(state = %ld, flags = %lx) \n",
p->comm, p->pid, cpu, p->state, p->flags);
}
write_unlock_irq(&tasklist_lock);
}
/* Take this CPU down. */
static int take_cpu_down(void *unused)
{
int err;
/* Ensure this CPU doesn't handle any more interrupts. */
err = __cpu_disable();
if (err < 0)
return err;
/* Force idle task to run as soon as we yield: it should
immediately notice cpu is offline and die quickly. */
sched_idle_next();
return 0;
}
/* Requires cpu_add_remove_lock to be held */
static int _cpu_down(unsigned int cpu)
{
int err;
struct task_struct *p;
cpumask_t old_allowed, tmp;
if (num_online_cpus() == 1)
return -EBUSY;
if (!cpu_online(cpu))
return -EINVAL;
err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
(void *)(long)cpu);
if (err == NOTIFY_BAD) {
printk("%s: attempt to take down CPU %u failed\n",
__FUNCTION__, cpu);
return -EINVAL;
}
/* Ensure that we are not runnable on dying cpu */
old_allowed = current->cpus_allowed;
tmp = CPU_MASK_ALL;
cpu_clear(cpu, tmp);
set_cpus_allowed(current, tmp);
mutex_lock(&cpu_bitmask_lock);
p = __stop_machine_run(take_cpu_down, NULL, cpu);
mutex_unlock(&cpu_bitmask_lock);
if (IS_ERR(p)) {
/* CPU didn't die: tell everyone. Can't complain. */
if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
(void *)(long)cpu) == NOTIFY_BAD)
BUG();
err = PTR_ERR(p);
goto out_allowed;
}
if (cpu_online(cpu))
goto out_thread;
/* Wait for it to sleep (leaving idle task). */
while (!idle_cpu(cpu))
yield();
/* This actually kills the CPU. */
__cpu_die(cpu);
/* Move it here so it can run. */
kthread_bind(p, get_cpu());
put_cpu();
/* CPU is completely dead: tell everyone. Too late to complain. */
if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD,
(void *)(long)cpu) == NOTIFY_BAD)
BUG();
check_for_tasks(cpu);
out_thread:
err = kthread_stop(p);
out_allowed:
set_cpus_allowed(current, old_allowed);
return err;
}
int cpu_down(unsigned int cpu)
{
int err = 0;
mutex_lock(&cpu_add_remove_lock);
if (cpu_hotplug_disabled)
err = -EBUSY;
else
err = _cpu_down(cpu);
mutex_unlock(&cpu_add_remove_lock);
return err;
}
#endif /*CONFIG_HOTPLUG_CPU*/
/* Requires cpu_add_remove_lock to be held */
static int __devinit _cpu_up(unsigned int cpu)
{
int ret;
void *hcpu = (void *)(long)cpu;
if (cpu_online(cpu) || !cpu_present(cpu))
return -EINVAL;
ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
if (ret == NOTIFY_BAD) {
printk("%s: attempt to bring up CPU %u failed\n",
__FUNCTION__, cpu);
ret = -EINVAL;
goto out_notify;
}
/* Arch-specific enabling code. */
mutex_lock(&cpu_bitmask_lock);
ret = __cpu_up(cpu);
mutex_unlock(&cpu_bitmask_lock);
if (ret != 0)
goto out_notify;
BUG_ON(!cpu_online(cpu));
/* Now call notifier in preparation. */
blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
out_notify:
if (ret != 0)
blocking_notifier_call_chain(&cpu_chain,
CPU_UP_CANCELED, hcpu);
return ret;
}
int __devinit cpu_up(unsigned int cpu)
{
int err = 0;
mutex_lock(&cpu_add_remove_lock);
if (cpu_hotplug_disabled)
err = -EBUSY;
else
err = _cpu_up(cpu);
mutex_unlock(&cpu_add_remove_lock);
return err;
}
#ifdef CONFIG_SUSPEND_SMP
static cpumask_t frozen_cpus;
int disable_nonboot_cpus(void)
{
int cpu, first_cpu, error;
mutex_lock(&cpu_add_remove_lock);
first_cpu = first_cpu(cpu_present_map);
if (!cpu_online(first_cpu)) {
error = _cpu_up(first_cpu);
if (error) {
printk(KERN_ERR "Could not bring CPU%d up.\n",
first_cpu);
goto out;
}
}
error = set_cpus_allowed(current, cpumask_of_cpu(first_cpu));
if (error) {
printk(KERN_ERR "Could not run on CPU%d\n", first_cpu);
goto out;
}
/* We take down all of the non-boot CPUs in one shot to avoid races
* with the userspace trying to use the CPU hotplug at the same time
*/
cpus_clear(frozen_cpus);
printk("Disabling non-boot CPUs ...\n");
for_each_online_cpu(cpu) {
if (cpu == first_cpu)
continue;
error = _cpu_down(cpu);
if (!error) {
cpu_set(cpu, frozen_cpus);
printk("CPU%d is down\n", cpu);
} else {
printk(KERN_ERR "Error taking CPU%d down: %d\n",
cpu, error);
break;
}
}
if (!error) {
BUG_ON(num_online_cpus() > 1);
/* Make sure the CPUs won't be enabled by someone else */
cpu_hotplug_disabled = 1;
} else {
printk(KERN_ERR "Non-boot CPUs are not disabled");
}
out:
mutex_unlock(&cpu_add_remove_lock);
return error;
}
void enable_nonboot_cpus(void)
{
int cpu, error;
/* Allow everyone to use the CPU hotplug again */
mutex_lock(&cpu_add_remove_lock);
cpu_hotplug_disabled = 0;
mutex_unlock(&cpu_add_remove_lock);
printk("Enabling non-boot CPUs ...\n");
for_each_cpu_mask(cpu, frozen_cpus) {
error = cpu_up(cpu);
if (!error) {
printk("CPU%d is up\n", cpu);
continue;
}
printk(KERN_WARNING "Error taking CPU%d up: %d\n",
cpu, error);
}
cpus_clear(frozen_cpus);
}
#endif
