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415 lines
9.7 KiB
415 lines
9.7 KiB
/* CPU control.
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* (C) 2001, 2002, 2003, 2004 Rusty Russell
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*
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* This code is licenced under the GPL.
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*/
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#include <linux/proc_fs.h>
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#include <linux/smp.h>
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#include <linux/init.h>
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#include <linux/notifier.h>
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#include <linux/sched.h>
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#include <linux/unistd.h>
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#include <linux/cpu.h>
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#include <linux/module.h>
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#include <linux/kthread.h>
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#include <linux/stop_machine.h>
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#include <linux/mutex.h>
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/* Serializes the updates to cpu_online_map, cpu_present_map */
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static DEFINE_MUTEX(cpu_add_remove_lock);
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static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain);
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/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
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* Should always be manipulated under cpu_add_remove_lock
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*/
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static int cpu_hotplug_disabled;
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static struct {
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struct task_struct *active_writer;
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struct mutex lock; /* Synchronizes accesses to refcount, */
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/*
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* Also blocks the new readers during
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* an ongoing cpu hotplug operation.
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*/
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int refcount;
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wait_queue_head_t writer_queue;
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} cpu_hotplug;
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#define writer_exists() (cpu_hotplug.active_writer != NULL)
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void __init cpu_hotplug_init(void)
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{
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cpu_hotplug.active_writer = NULL;
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mutex_init(&cpu_hotplug.lock);
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cpu_hotplug.refcount = 0;
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init_waitqueue_head(&cpu_hotplug.writer_queue);
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}
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#ifdef CONFIG_HOTPLUG_CPU
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void get_online_cpus(void)
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{
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might_sleep();
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if (cpu_hotplug.active_writer == current)
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return;
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mutex_lock(&cpu_hotplug.lock);
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cpu_hotplug.refcount++;
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mutex_unlock(&cpu_hotplug.lock);
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}
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EXPORT_SYMBOL_GPL(get_online_cpus);
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void put_online_cpus(void)
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{
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if (cpu_hotplug.active_writer == current)
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return;
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mutex_lock(&cpu_hotplug.lock);
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cpu_hotplug.refcount--;
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if (unlikely(writer_exists()) && !cpu_hotplug.refcount)
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wake_up(&cpu_hotplug.writer_queue);
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mutex_unlock(&cpu_hotplug.lock);
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}
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EXPORT_SYMBOL_GPL(put_online_cpus);
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#endif /* CONFIG_HOTPLUG_CPU */
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/*
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* The following two API's must be used when attempting
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* to serialize the updates to cpu_online_map, cpu_present_map.
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*/
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void cpu_maps_update_begin(void)
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{
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mutex_lock(&cpu_add_remove_lock);
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}
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void cpu_maps_update_done(void)
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{
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mutex_unlock(&cpu_add_remove_lock);
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}
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/*
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* This ensures that the hotplug operation can begin only when the
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* refcount goes to zero.
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*
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* Note that during a cpu-hotplug operation, the new readers, if any,
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* will be blocked by the cpu_hotplug.lock
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*
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* Since cpu_maps_update_begin is always called after invoking
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* cpu_maps_update_begin, we can be sure that only one writer is active.
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*
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* Note that theoretically, there is a possibility of a livelock:
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* - Refcount goes to zero, last reader wakes up the sleeping
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* writer.
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* - Last reader unlocks the cpu_hotplug.lock.
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* - A new reader arrives at this moment, bumps up the refcount.
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* - The writer acquires the cpu_hotplug.lock finds the refcount
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* non zero and goes to sleep again.
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*
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* However, this is very difficult to achieve in practice since
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* get_online_cpus() not an api which is called all that often.
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*
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*/
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static void cpu_hotplug_begin(void)
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{
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DECLARE_WAITQUEUE(wait, current);
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mutex_lock(&cpu_hotplug.lock);
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cpu_hotplug.active_writer = current;
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add_wait_queue_exclusive(&cpu_hotplug.writer_queue, &wait);
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while (cpu_hotplug.refcount) {
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set_current_state(TASK_UNINTERRUPTIBLE);
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mutex_unlock(&cpu_hotplug.lock);
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schedule();
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mutex_lock(&cpu_hotplug.lock);
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}
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remove_wait_queue_locked(&cpu_hotplug.writer_queue, &wait);
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}
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static void cpu_hotplug_done(void)
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{
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cpu_hotplug.active_writer = NULL;
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mutex_unlock(&cpu_hotplug.lock);
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}
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/* Need to know about CPUs going up/down? */
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int __cpuinit register_cpu_notifier(struct notifier_block *nb)
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{
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int ret;
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cpu_maps_update_begin();
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ret = raw_notifier_chain_register(&cpu_chain, nb);
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cpu_maps_update_done();
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return ret;
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}
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#ifdef CONFIG_HOTPLUG_CPU
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EXPORT_SYMBOL(register_cpu_notifier);
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void unregister_cpu_notifier(struct notifier_block *nb)
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{
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cpu_maps_update_begin();
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raw_notifier_chain_unregister(&cpu_chain, nb);
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cpu_maps_update_done();
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}
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EXPORT_SYMBOL(unregister_cpu_notifier);
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static inline void check_for_tasks(int cpu)
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{
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struct task_struct *p;
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write_lock_irq(&tasklist_lock);
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for_each_process(p) {
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if (task_cpu(p) == cpu &&
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(!cputime_eq(p->utime, cputime_zero) ||
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!cputime_eq(p->stime, cputime_zero)))
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printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
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(state = %ld, flags = %x) \n",
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p->comm, task_pid_nr(p), cpu,
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p->state, p->flags);
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}
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write_unlock_irq(&tasklist_lock);
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}
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struct take_cpu_down_param {
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unsigned long mod;
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void *hcpu;
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};
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/* Take this CPU down. */
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static int take_cpu_down(void *_param)
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{
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struct take_cpu_down_param *param = _param;
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int err;
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raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
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param->hcpu);
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/* Ensure this CPU doesn't handle any more interrupts. */
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err = __cpu_disable();
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if (err < 0)
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return err;
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/* Force idle task to run as soon as we yield: it should
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immediately notice cpu is offline and die quickly. */
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sched_idle_next();
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return 0;
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}
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/* Requires cpu_add_remove_lock to be held */
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static int _cpu_down(unsigned int cpu, int tasks_frozen)
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{
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int err, nr_calls = 0;
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struct task_struct *p;
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cpumask_t old_allowed, tmp;
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void *hcpu = (void *)(long)cpu;
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unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
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struct take_cpu_down_param tcd_param = {
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.mod = mod,
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.hcpu = hcpu,
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};
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if (num_online_cpus() == 1)
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return -EBUSY;
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if (!cpu_online(cpu))
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return -EINVAL;
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cpu_hotplug_begin();
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err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
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hcpu, -1, &nr_calls);
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if (err == NOTIFY_BAD) {
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nr_calls--;
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__raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
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hcpu, nr_calls, NULL);
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printk("%s: attempt to take down CPU %u failed\n",
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__FUNCTION__, cpu);
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err = -EINVAL;
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goto out_release;
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}
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/* Ensure that we are not runnable on dying cpu */
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old_allowed = current->cpus_allowed;
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tmp = CPU_MASK_ALL;
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cpu_clear(cpu, tmp);
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set_cpus_allowed(current, tmp);
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p = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
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if (IS_ERR(p) || cpu_online(cpu)) {
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/* CPU didn't die: tell everyone. Can't complain. */
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if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
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hcpu) == NOTIFY_BAD)
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BUG();
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if (IS_ERR(p)) {
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err = PTR_ERR(p);
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goto out_allowed;
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}
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goto out_thread;
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}
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/* Wait for it to sleep (leaving idle task). */
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while (!idle_cpu(cpu))
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yield();
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/* This actually kills the CPU. */
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__cpu_die(cpu);
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/* CPU is completely dead: tell everyone. Too late to complain. */
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if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,
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hcpu) == NOTIFY_BAD)
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BUG();
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check_for_tasks(cpu);
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out_thread:
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err = kthread_stop(p);
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out_allowed:
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set_cpus_allowed(current, old_allowed);
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out_release:
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cpu_hotplug_done();
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return err;
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}
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int cpu_down(unsigned int cpu)
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{
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int err = 0;
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cpu_maps_update_begin();
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if (cpu_hotplug_disabled)
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err = -EBUSY;
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else
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err = _cpu_down(cpu, 0);
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cpu_maps_update_done();
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return err;
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}
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#endif /*CONFIG_HOTPLUG_CPU*/
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/* Requires cpu_add_remove_lock to be held */
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static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
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{
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int ret, nr_calls = 0;
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void *hcpu = (void *)(long)cpu;
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unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
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if (cpu_online(cpu) || !cpu_present(cpu))
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return -EINVAL;
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cpu_hotplug_begin();
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ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
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-1, &nr_calls);
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if (ret == NOTIFY_BAD) {
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nr_calls--;
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printk("%s: attempt to bring up CPU %u failed\n",
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__FUNCTION__, cpu);
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ret = -EINVAL;
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goto out_notify;
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}
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/* Arch-specific enabling code. */
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ret = __cpu_up(cpu);
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if (ret != 0)
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goto out_notify;
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BUG_ON(!cpu_online(cpu));
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/* Now call notifier in preparation. */
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raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
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out_notify:
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if (ret != 0)
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__raw_notifier_call_chain(&cpu_chain,
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CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
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cpu_hotplug_done();
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return ret;
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}
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int __cpuinit cpu_up(unsigned int cpu)
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{
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int err = 0;
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if (!cpu_isset(cpu, cpu_possible_map)) {
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printk(KERN_ERR "can't online cpu %d because it is not "
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"configured as may-hotadd at boot time\n", cpu);
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#if defined(CONFIG_IA64) || defined(CONFIG_X86_64) || defined(CONFIG_S390)
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printk(KERN_ERR "please check additional_cpus= boot "
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"parameter\n");
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#endif
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return -EINVAL;
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}
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cpu_maps_update_begin();
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if (cpu_hotplug_disabled)
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err = -EBUSY;
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else
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err = _cpu_up(cpu, 0);
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cpu_maps_update_done();
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return err;
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}
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#ifdef CONFIG_PM_SLEEP_SMP
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static cpumask_t frozen_cpus;
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int disable_nonboot_cpus(void)
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{
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int cpu, first_cpu, error = 0;
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cpu_maps_update_begin();
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first_cpu = first_cpu(cpu_online_map);
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/* We take down all of the non-boot CPUs in one shot to avoid races
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* with the userspace trying to use the CPU hotplug at the same time
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*/
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cpus_clear(frozen_cpus);
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printk("Disabling non-boot CPUs ...\n");
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for_each_online_cpu(cpu) {
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if (cpu == first_cpu)
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continue;
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error = _cpu_down(cpu, 1);
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if (!error) {
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cpu_set(cpu, frozen_cpus);
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printk("CPU%d is down\n", cpu);
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} else {
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printk(KERN_ERR "Error taking CPU%d down: %d\n",
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cpu, error);
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break;
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}
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}
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if (!error) {
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BUG_ON(num_online_cpus() > 1);
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/* Make sure the CPUs won't be enabled by someone else */
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cpu_hotplug_disabled = 1;
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} else {
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printk(KERN_ERR "Non-boot CPUs are not disabled\n");
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}
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cpu_maps_update_done();
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return error;
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}
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void enable_nonboot_cpus(void)
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{
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int cpu, error;
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/* Allow everyone to use the CPU hotplug again */
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cpu_maps_update_begin();
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cpu_hotplug_disabled = 0;
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if (cpus_empty(frozen_cpus))
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goto out;
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printk("Enabling non-boot CPUs ...\n");
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for_each_cpu_mask(cpu, frozen_cpus) {
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error = _cpu_up(cpu, 1);
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if (!error) {
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printk("CPU%d is up\n", cpu);
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continue;
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}
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printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
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}
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cpus_clear(frozen_cpus);
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out:
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cpu_maps_update_done();
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}
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#endif /* CONFIG_PM_SLEEP_SMP */
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