/* 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_SMPstatic 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