| /* 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_SMP |
| static 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 |