| /* 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> |
| |
| /* |
| * Represents all cpu's present in the system |
| * In systems capable of hotplug, this map could dynamically grow |
| * as new cpu's are detected in the system via any platform specific |
| * method, such as ACPI for e.g. |
| */ |
| cpumask_t cpu_present_map __read_mostly; |
| EXPORT_SYMBOL(cpu_present_map); |
| |
| #ifndef CONFIG_SMP |
| |
| /* |
| * Represents all cpu's that are currently online. |
| */ |
| cpumask_t cpu_online_map __read_mostly = CPU_MASK_ALL; |
| EXPORT_SYMBOL(cpu_online_map); |
| |
| cpumask_t cpu_possible_map __read_mostly = CPU_MASK_ALL; |
| EXPORT_SYMBOL(cpu_possible_map); |
| |
| #else /* CONFIG_SMP */ |
| |
| /* 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; |
| } cpu_hotplug; |
| |
| void __init cpu_hotplug_init(void) |
| { |
| cpu_hotplug.active_writer = NULL; |
| mutex_init(&cpu_hotplug.lock); |
| cpu_hotplug.refcount = 0; |
| } |
| |
| #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); |
| if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer)) |
| wake_up_process(cpu_hotplug.active_writer); |
| 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_hotplug_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) |
| { |
| cpu_hotplug.active_writer = current; |
| |
| for (;;) { |
| mutex_lock(&cpu_hotplug.lock); |
| if (likely(!cpu_hotplug.refcount)) |
| break; |
| __set_current_state(TASK_UNINTERRUPTIBLE); |
| mutex_unlock(&cpu_hotplug.lock); |
| schedule(); |
| } |
| } |
| |
| 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 __ref 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 __ref 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 __ref 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 __ref _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", |
| __func__, cpu); |
| err = -EINVAL; |
| goto out_release; |
| } |
| |
| /* Ensure that we are not runnable on dying cpu */ |
| old_allowed = current->cpus_allowed; |
| cpus_setall(tmp); |
| cpu_clear(cpu, tmp); |
| set_cpus_allowed_ptr(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_ptr(current, &old_allowed); |
| out_release: |
| cpu_hotplug_done(); |
| return err; |
| } |
| |
| int __ref 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", |
| __func__, 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_SMP |
| static 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 */ |
| |
| #endif /* CONFIG_SMP */ |