/* 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 <asm/semaphore.h>
/* This protects CPUs going up and down... */
DECLARE_MUTEX(cpucontrol);
EXPORT_SYMBOL_GPL(cpucontrol);
static struct notifier_block *cpu_chain;
/*
* Used to check by callers if they need to acquire the cpucontrol
* or not to protect a cpu from being removed. Its sometimes required to
* call these functions both for normal operations, and in response to
* a cpu being added/removed. If the context of the call is in the same
* thread context as a CPU hotplug thread, we dont need to take the lock
* since its already protected
* check drivers/cpufreq/cpufreq.c for its usage - Ashok Raj
*/
int current_in_cpu_hotplug(void)
{
return (current->flags & PF_HOTPLUG_CPU);
}
EXPORT_SYMBOL_GPL(current_in_cpu_hotplug);
/* Need to know about CPUs going up/down? */
int register_cpu_notifier(struct notifier_block *nb)
{
int ret;
if ((ret = down_interruptible(&cpucontrol)) != 0)
return ret;
ret = notifier_chain_register(&cpu_chain, nb);
up(&cpucontrol);
return ret;
}
EXPORT_SYMBOL(register_cpu_notifier);
void unregister_cpu_notifier(struct notifier_block *nb)
{
down(&cpucontrol);
notifier_chain_unregister(&cpu_chain, nb);
up(&cpucontrol);
}
EXPORT_SYMBOL(unregister_cpu_notifier);
#ifdef CONFIG_HOTPLUG_CPU
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;
}
int cpu_down(unsigned int cpu)
{
int err;
struct task_struct *p;
cpumask_t old_allowed, tmp;
if ((err = lock_cpu_hotplug_interruptible()) != 0)
return err;
if (num_online_cpus() == 1) {
err = -EBUSY;
goto out;
}
if (!cpu_online(cpu)) {
err = -EINVAL;
goto out;
}
/*
* Leave a trace in current->flags indicating we are already in
* process of performing CPU hotplug. Callers can check if cpucontrol
* is already acquired by current thread, and if so not cause
* a dead lock by not acquiring the lock
*/
current->flags |= PF_HOTPLUG_CPU;
err = 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);
err = -EINVAL;
goto out;
}
/* 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);
p = __stop_machine_run(take_cpu_down, NULL, cpu);
if (IS_ERR(p)) {
/* CPU didn't die: tell everyone. Can't complain. */
if (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 (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);
out:
current->flags &= ~PF_HOTPLUG_CPU;
unlock_cpu_hotplug();
return err;
}
#endif /*CONFIG_HOTPLUG_CPU*/
int __devinit cpu_up(unsigned int cpu)
{
int ret;
void *hcpu = (void *)(long)cpu;
if ((ret = down_interruptible(&cpucontrol)) != 0)
return ret;
if (cpu_online(cpu) || !cpu_present(cpu)) {
ret = -EINVAL;
goto out;
}
/*
* Leave a trace in current->flags indicating we are already in
* process of performing CPU hotplug.
*/
current->flags |= PF_HOTPLUG_CPU;
ret = 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. */
ret = __cpu_up(cpu);
if (ret != 0)
goto out_notify;
if (!cpu_online(cpu))
BUG();
/* Now call notifier in preparation. */
notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
out_notify:
if (ret != 0)
notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu);
out:
current->flags &= ~PF_HOTPLUG_CPU;
up(&cpucontrol);
return ret;
}
