/* 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> /* Serializes the updates to cpu_online_map, cpu_present_map */static DEFINE_MUTEX(cpu_add_remove_lock); static __cpuinitdata RAW_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; static struct {	struct task_struct *active_writer;	struct mutex lock; /* Synchronizes accesses to refcount, */	/*	 * Also blocks the new readers during	 * an ongoing cpu hotplug operation.	 */	int refcount;	wait_queue_head_t writer_queue;} cpu_hotplug; #define writer_exists() (cpu_hotplug.active_writer != NULL) void __init cpu_hotplug_init(void){	cpu_hotplug.active_writer = NULL;	mutex_init(&cpu_hotplug.lock);	cpu_hotplug.refcount = 0;	init_waitqueue_head(&cpu_hotplug.writer_queue);} #ifdef CONFIG_HOTPLUG_CPU void get_online_cpus(void){	might_sleep();	if (cpu_hotplug.active_writer == current)		return;	mutex_lock(&cpu_hotplug.lock);	cpu_hotplug.refcount++;	mutex_unlock(&cpu_hotplug.lock); }EXPORT_SYMBOL_GPL(get_online_cpus); void put_online_cpus(void){	if (cpu_hotplug.active_writer == current)		return;	mutex_lock(&cpu_hotplug.lock);	cpu_hotplug.refcount--; 	if (unlikely(writer_exists()) && !cpu_hotplug.refcount)		wake_up(&cpu_hotplug.writer_queue); 	mutex_unlock(&cpu_hotplug.lock); }EXPORT_SYMBOL_GPL(put_online_cpus); #endif	/* CONFIG_HOTPLUG_CPU */ /* * The following two API's must be used when attempting * to serialize the updates to cpu_online_map, cpu_present_map. */void cpu_maps_update_begin(void){	mutex_lock(&cpu_add_remove_lock);} void cpu_maps_update_done(void){	mutex_unlock(&cpu_add_remove_lock);} /* * This ensures that the hotplug operation can begin only when the * refcount goes to zero. * * Note that during a cpu-hotplug operation, the new readers, if any, * will be blocked by the cpu_hotplug.lock * * Since cpu_maps_update_begin is always called after invoking * cpu_maps_update_begin, we can be sure that only one writer is active. * * Note that theoretically, there is a possibility of a livelock: * - Refcount goes to zero, last reader wakes up the sleeping *   writer. * - Last reader unlocks the cpu_hotplug.lock. * - A new reader arrives at this moment, bumps up the refcount. * - The writer acquires the cpu_hotplug.lock finds the refcount *   non zero and goes to sleep again. * * However, this is very difficult to achieve in practice since * get_online_cpus() not an api which is called all that often. * */static void cpu_hotplug_begin(void){	DECLARE_WAITQUEUE(wait, current); 	mutex_lock(&cpu_hotplug.lock); 	cpu_hotplug.active_writer = current;	add_wait_queue_exclusive(&cpu_hotplug.writer_queue, &wait);	while (cpu_hotplug.refcount) {		set_current_state(TASK_UNINTERRUPTIBLE);		mutex_unlock(&cpu_hotplug.lock);		schedule();		mutex_lock(&cpu_hotplug.lock);	}	remove_wait_queue_locked(&cpu_hotplug.writer_queue, &wait);} static void cpu_hotplug_done(void){	cpu_hotplug.active_writer = NULL;	mutex_unlock(&cpu_hotplug.lock);}/* Need to know about CPUs going up/down? */int __cpuinit register_cpu_notifier(struct notifier_block *nb){	int ret;	cpu_maps_update_begin();	ret = raw_notifier_chain_register(&cpu_chain, nb);	cpu_maps_update_done();	return ret;} #ifdef CONFIG_HOTPLUG_CPU EXPORT_SYMBOL(register_cpu_notifier); void unregister_cpu_notifier(struct notifier_block *nb){	cpu_maps_update_begin();	raw_notifier_chain_unregister(&cpu_chain, nb);	cpu_maps_update_done();}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 = %x) \n",				 p->comm, task_pid_nr(p), cpu,				 p->state, p->flags);	}	write_unlock_irq(&tasklist_lock);} struct take_cpu_down_param {	unsigned long mod;	void *hcpu;}; /* Take this CPU down. */static int take_cpu_down(void *_param){	struct take_cpu_down_param *param = _param;	int err; 	raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,				param->hcpu);	/* 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 tasks_frozen){	int err, nr_calls = 0;	struct task_struct *p;	cpumask_t old_allowed, tmp;	void *hcpu = (void *)(long)cpu;	unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;	struct take_cpu_down_param tcd_param = {		.mod = mod,		.hcpu = hcpu,	}; 	if (num_online_cpus() == 1)		return -EBUSY; 	if (!cpu_online(cpu))		return -EINVAL; 	cpu_hotplug_begin();	err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,					hcpu, -1, &nr_calls);	if (err == NOTIFY_BAD) {		nr_calls--;		__raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,					  hcpu, nr_calls, NULL);		printk("%s: attempt to take down CPU %u failed\n",				__FUNCTION__, cpu);		err = -EINVAL;		goto out_release;	} 	/* 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, &tcd_param, cpu); 	if (IS_ERR(p) || cpu_online(cpu)) {		/* CPU didn't die: tell everyone.  Can't complain. */		if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,					    hcpu) == NOTIFY_BAD)			BUG(); 		if (IS_ERR(p)) {			err = PTR_ERR(p);			goto out_allowed;		}		goto out_thread;	} 	/* Wait for it to sleep (leaving idle task). */	while (!idle_cpu(cpu))		yield(); 	/* This actually kills the CPU. */	__cpu_die(cpu); 	/* CPU is completely dead: tell everyone.  Too late to complain. */	if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,				    hcpu) == NOTIFY_BAD)		BUG(); 	check_for_tasks(cpu); out_thread:	err = kthread_stop(p);out_allowed:	set_cpus_allowed(current, old_allowed);out_release:	cpu_hotplug_done();	return err;} int cpu_down(unsigned int cpu){	int err = 0; 	cpu_maps_update_begin();	if (cpu_hotplug_disabled)		err = -EBUSY;	else		err = _cpu_down(cpu, 0); 	cpu_maps_update_done();	return err;}#endif /*CONFIG_HOTPLUG_CPU*/ /* Requires cpu_add_remove_lock to be held */static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen){	int ret, nr_calls = 0;	void *hcpu = (void *)(long)cpu;	unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0; 	if (cpu_online(cpu) || !cpu_present(cpu))		return -EINVAL; 	cpu_hotplug_begin();	ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,							-1, &nr_calls);	if (ret == NOTIFY_BAD) {		nr_calls--;		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;	BUG_ON(!cpu_online(cpu)); 	/* Now call notifier in preparation. */	raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu); out_notify:	if (ret != 0)		__raw_notifier_call_chain(&cpu_chain,				CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);	cpu_hotplug_done(); 	return ret;} int __cpuinit cpu_up(unsigned int cpu){	int err = 0;	if (!cpu_isset(cpu, cpu_possible_map)) {		printk(KERN_ERR "can't online cpu %d because it is not "			"configured as may-hotadd at boot time\n", cpu);#if defined(CONFIG_IA64) || defined(CONFIG_X86_64) || defined(CONFIG_S390)		printk(KERN_ERR "please check additional_cpus= boot "				"parameter\n");#endif		return -EINVAL;	} 	cpu_maps_update_begin();	if (cpu_hotplug_disabled)		err = -EBUSY;	else		err = _cpu_up(cpu, 0); 	cpu_maps_update_done();	return err;} #ifdef CONFIG_PM_SLEEP_SMPstatic cpumask_t frozen_cpus; int disable_nonboot_cpus(void){	int cpu, first_cpu, error = 0; 	cpu_maps_update_begin();	first_cpu = first_cpu(cpu_online_map);	/* 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, 1);		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\n");	}	cpu_maps_update_done();	return error;} void __ref enable_nonboot_cpus(void){	int cpu, error; 	/* Allow everyone to use the CPU hotplug again */	cpu_maps_update_begin();	cpu_hotplug_disabled = 0;	if (cpus_empty(frozen_cpus))		goto out; 	printk("Enabling non-boot CPUs ...\n");	for_each_cpu_mask(cpu, frozen_cpus) {		error = _cpu_up(cpu, 1);		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);out:	cpu_maps_update_done();}#endif /* CONFIG_PM_SLEEP_SMP */