/* 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> #ifdef CONFIG_SMP /* Serializes the updates to cpu_online_mask, cpu_present_mask */ 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 = { .active_writer = NULL, .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock), .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_mask, cpu_present_mask. */ 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; /* Ensure this CPU doesn't handle any more interrupts. */ err = __cpu_disable(); if (err < 0) return err; raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod, param->hcpu); /* 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; cpumask_var_t old_allowed; 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; if (!alloc_cpumask_var(&old_allowed, GFP_KERNEL)) return -ENOMEM; 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 */ cpumask_copy(old_allowed, ¤t->cpus_allowed); set_cpus_allowed_ptr(current, cpumask_of(cpumask_any_but(cpu_online_mask, cpu))); err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu)); if (err) { /* CPU didn't die: tell everyone. Can't complain. */ if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod, hcpu) == NOTIFY_BAD) BUG(); goto out_allowed; } BUG_ON(cpu_online(cpu)); /* 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_allowed: set_cpus_allowed_ptr(current, old_allowed); out_release: cpu_hotplug_done(); if (!err) { if (raw_notifier_call_chain(&cpu_chain, CPU_POST_DEAD | mod, hcpu) == NOTIFY_BAD) BUG(); } free_cpumask_var(old_allowed); return err; } int __ref cpu_down(unsigned int cpu) { int err; err = stop_machine_create(); if (err) return err; cpu_maps_update_begin(); if (cpu_hotplug_disabled) { err = -EBUSY; goto out; } set_cpu_active(cpu, false); /* * Make sure the all cpus did the reschedule and are not * using stale version of the cpu_active_mask. * This is not strictly necessary becuase stop_machine() * that we run down the line already provides the required * synchronization. But it's really a side effect and we do not * want to depend on the innards of the stop_machine here. */ synchronize_sched(); err = _cpu_down(cpu, 0); if (cpu_online(cpu)) set_cpu_active(cpu, true); out: cpu_maps_update_done(); stop_machine_destroy(); return err; } EXPORT_SYMBOL(cpu_down); #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)); set_cpu_active(cpu, true); /* 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_possible(cpu)) { 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) printk(KERN_ERR "please check additional_cpus= boot " "parameter\n"); #endif return -EINVAL; } cpu_maps_update_begin(); if (cpu_hotplug_disabled) { err = -EBUSY; goto out; } err = _cpu_up(cpu, 0); out: cpu_maps_update_done(); return err; } #ifdef CONFIG_PM_SLEEP_SMP static cpumask_var_t frozen_cpus; int disable_nonboot_cpus(void) { int cpu, first_cpu, error; error = stop_machine_create(); if (error) return error; cpu_maps_update_begin(); first_cpu = cpumask_first(cpu_online_mask); /* 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 */ cpumask_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) cpumask_set_cpu(cpu, frozen_cpus); 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(); stop_machine_destroy(); return error; } void __weak arch_enable_nonboot_cpus_begin(void) { } void __weak arch_enable_nonboot_cpus_end(void) { } 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 (cpumask_empty(frozen_cpus)) goto out; printk("Enabling non-boot CPUs ...\n"); arch_enable_nonboot_cpus_begin(); for_each_cpu(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); } arch_enable_nonboot_cpus_end(); cpumask_clear(frozen_cpus); out: cpu_maps_update_done(); } static int alloc_frozen_cpus(void) { if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO)) return -ENOMEM; return 0; } core_initcall(alloc_frozen_cpus); #endif /* CONFIG_PM_SLEEP_SMP */ /** * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers * @cpu: cpu that just started * * This function calls the cpu_chain notifiers with CPU_STARTING. * It must be called by the arch code on the new cpu, before the new cpu * enables interrupts and before the "boot" cpu returns from __cpu_up(). */ void __cpuinit notify_cpu_starting(unsigned int cpu) { unsigned long val = CPU_STARTING; #ifdef CONFIG_PM_SLEEP_SMP if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus)) val = CPU_STARTING_FROZEN; #endif /* CONFIG_PM_SLEEP_SMP */ raw_notifier_call_chain(&cpu_chain, val, (void *)(long)cpu); } #endif /* CONFIG_SMP */ /* * cpu_bit_bitmap[] is a special, "compressed" data structure that * represents all NR_CPUS bits binary values of 1<<nr. * * It is used by cpumask_of() to get a constant address to a CPU * mask value that has a single bit set only. */ /* cpu_bit_bitmap[0] is empty - so we can back into it */ #define MASK_DECLARE_1(x) [x+1][0] = 1UL << (x) #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1) #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2) #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4) const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = { MASK_DECLARE_8(0), MASK_DECLARE_8(8), MASK_DECLARE_8(16), MASK_DECLARE_8(24), #if BITS_PER_LONG > 32 MASK_DECLARE_8(32), MASK_DECLARE_8(40), MASK_DECLARE_8(48), MASK_DECLARE_8(56), #endif }; EXPORT_SYMBOL_GPL(cpu_bit_bitmap); const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL; EXPORT_SYMBOL(cpu_all_bits); #ifdef CONFIG_INIT_ALL_POSSIBLE static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly = CPU_BITS_ALL; #else static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly; #endif const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits); EXPORT_SYMBOL(cpu_possible_mask); static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly; const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits); EXPORT_SYMBOL(cpu_online_mask); static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly; const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits); EXPORT_SYMBOL(cpu_present_mask); static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly; const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits); EXPORT_SYMBOL(cpu_active_mask); void set_cpu_possible(unsigned int cpu, bool possible) { if (possible) cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits)); else cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits)); } void set_cpu_present(unsigned int cpu, bool present) { if (present) cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits)); else cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits)); } void set_cpu_online(unsigned int cpu, bool online) { if (online) cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits)); else cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits)); } void set_cpu_active(unsigned int cpu, bool active) { if (active) cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits)); else cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits)); } void init_cpu_present(const struct cpumask *src) { cpumask_copy(to_cpumask(cpu_present_bits), src); } void init_cpu_possible(const struct cpumask *src) { cpumask_copy(to_cpumask(cpu_possible_bits), src); } void init_cpu_online(const struct cpumask *src) { cpumask_copy(to_cpumask(cpu_online_bits), src); }