324 lines
7.0 KiB
C
324 lines
7.0 KiB
C
/* 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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/* This protects CPUs going up and down... */
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static DEFINE_MUTEX(cpu_add_remove_lock);
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static DEFINE_MUTEX(cpu_bitmask_lock);
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static __cpuinitdata BLOCKING_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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#ifdef CONFIG_HOTPLUG_CPU
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/* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
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static struct task_struct *recursive;
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static int recursive_depth;
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void lock_cpu_hotplug(void)
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{
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struct task_struct *tsk = current;
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if (tsk == recursive) {
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static int warnings = 10;
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if (warnings) {
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printk(KERN_ERR "Lukewarm IQ detected in hotplug locking\n");
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WARN_ON(1);
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warnings--;
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}
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recursive_depth++;
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return;
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}
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mutex_lock(&cpu_bitmask_lock);
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recursive = tsk;
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}
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EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
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void unlock_cpu_hotplug(void)
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{
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WARN_ON(recursive != current);
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if (recursive_depth) {
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recursive_depth--;
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return;
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}
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mutex_unlock(&cpu_bitmask_lock);
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recursive = NULL;
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}
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EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
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#endif /* CONFIG_HOTPLUG_CPU */
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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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return blocking_notifier_chain_register(&cpu_chain, nb);
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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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blocking_notifier_chain_unregister(&cpu_chain, nb);
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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 = %lx) \n",
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p->comm, p->pid, cpu, 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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/* Take this CPU down. */
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static int take_cpu_down(void *unused)
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{
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int err;
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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)
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{
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int err;
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struct task_struct *p;
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cpumask_t old_allowed, tmp;
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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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err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
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(void *)(long)cpu);
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if (err == NOTIFY_BAD) {
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printk("%s: attempt to take down CPU %u failed\n",
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__FUNCTION__, cpu);
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return -EINVAL;
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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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mutex_lock(&cpu_bitmask_lock);
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p = __stop_machine_run(take_cpu_down, NULL, cpu);
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mutex_unlock(&cpu_bitmask_lock);
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if (IS_ERR(p)) {
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/* CPU didn't die: tell everyone. Can't complain. */
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if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
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(void *)(long)cpu) == NOTIFY_BAD)
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BUG();
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err = PTR_ERR(p);
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goto out_allowed;
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}
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if (cpu_online(cpu))
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goto out_thread;
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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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/* Move it here so it can run. */
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kthread_bind(p, get_cpu());
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put_cpu();
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/* CPU is completely dead: tell everyone. Too late to complain. */
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if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD,
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(void *)(long)cpu) == 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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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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mutex_lock(&cpu_add_remove_lock);
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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);
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mutex_unlock(&cpu_add_remove_lock);
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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 __devinit _cpu_up(unsigned int cpu)
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{
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int ret;
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void *hcpu = (void *)(long)cpu;
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if (cpu_online(cpu) || !cpu_present(cpu))
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return -EINVAL;
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ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
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if (ret == NOTIFY_BAD) {
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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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mutex_lock(&cpu_bitmask_lock);
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ret = __cpu_up(cpu);
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mutex_unlock(&cpu_bitmask_lock);
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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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blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
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out_notify:
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if (ret != 0)
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blocking_notifier_call_chain(&cpu_chain,
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CPU_UP_CANCELED, hcpu);
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return ret;
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}
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int __devinit cpu_up(unsigned int cpu)
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{
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int err = 0;
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mutex_lock(&cpu_add_remove_lock);
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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);
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mutex_unlock(&cpu_add_remove_lock);
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return err;
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}
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#ifdef CONFIG_SUSPEND_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;
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mutex_lock(&cpu_add_remove_lock);
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first_cpu = first_cpu(cpu_present_map);
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if (!cpu_online(first_cpu)) {
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error = _cpu_up(first_cpu);
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if (error) {
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printk(KERN_ERR "Could not bring CPU%d up.\n",
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first_cpu);
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goto out;
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}
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}
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error = set_cpus_allowed(current, cpumask_of_cpu(first_cpu));
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if (error) {
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printk(KERN_ERR "Could not run on CPU%d\n", first_cpu);
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goto out;
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}
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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);
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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");
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}
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out:
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mutex_unlock(&cpu_add_remove_lock);
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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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mutex_lock(&cpu_add_remove_lock);
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cpu_hotplug_disabled = 0;
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mutex_unlock(&cpu_add_remove_lock);
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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);
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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",
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cpu, error);
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}
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cpus_clear(frozen_cpus);
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}
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#endif
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