X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=kernel%2Fcpu.c;h=e0d3a4f56ecbddb4a4c87c714bc49991fefa2cc2;hb=cd58289667293593b04fd315ec7f2f37589134cb;hp=53d8263ae12ebc00483a3ad999177799003467e2;hpb=f370513640492641b4046bfd9a6e4714f6ae530d;p=safe%2Fjmp%2Flinux-2.6 diff --git a/kernel/cpu.c b/kernel/cpu.c index 53d8263..e0d3a4f 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -13,35 +13,150 @@ #include #include #include -#include +#include -/* This protects CPUs going up and down... */ -DECLARE_MUTEX(cpucontrol); +/* Serializes the updates to cpu_online_map, cpu_present_map */ +static DEFINE_MUTEX(cpu_add_remove_lock); -static struct notifier_block *cpu_chain; +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 register_cpu_notifier(struct notifier_block *nb) +int __cpuinit register_cpu_notifier(struct notifier_block *nb) { int ret; - - if ((ret = down_interruptible(&cpucontrol)) != 0) - return ret; - ret = notifier_chain_register(&cpu_chain, nb); - up(&cpucontrol); + 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) { - down(&cpucontrol); - notifier_chain_unregister(&cpu_chain, nb); - up(&cpucontrol); + cpu_maps_update_begin(); + raw_notifier_chain_unregister(&cpu_chain, nb); + cpu_maps_update_done(); } EXPORT_SYMBOL(unregister_cpu_notifier); -#ifdef CONFIG_HOTPLUG_CPU static inline void check_for_tasks(int cpu) { struct task_struct *p; @@ -52,17 +167,26 @@ static inline void check_for_tasks(int 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); + (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 *unused) +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) @@ -74,32 +198,36 @@ static int take_cpu_down(void *unused) return 0; } -int cpu_down(unsigned int cpu) +/* Requires cpu_add_remove_lock to be held */ +static int _cpu_down(unsigned int cpu, int tasks_frozen) { - int err; + 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 ((err = lock_cpu_hotplug_interruptible()) != 0) - return err; + if (num_online_cpus() == 1) + return -EBUSY; - if (num_online_cpus() == 1) { - err = -EBUSY; - goto out; - } - - if (!cpu_online(cpu)) { - err = -EINVAL; - goto out; - } + if (!cpu_online(cpu)) + return -EINVAL; - err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, - (void *)(long)cpu); + 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; + goto out_release; } /* Ensure that we are not runnable on dying cpu */ @@ -108,19 +236,20 @@ int cpu_down(unsigned int cpu) cpu_clear(cpu, tmp); set_cpus_allowed(current, tmp); - p = __stop_machine_run(take_cpu_down, NULL, cpu); - if (IS_ERR(p)) { + 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 (notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, - (void *)(long)cpu) == NOTIFY_BAD) + if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod, + hcpu) == NOTIFY_BAD) BUG(); - err = PTR_ERR(p); - goto out_allowed; - } - - if (cpu_online(cpu)) + 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)) @@ -129,13 +258,9 @@ int cpu_down(unsigned int cpu) /* 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 (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu) - == NOTIFY_BAD) + if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod, + hcpu) == NOTIFY_BAD) BUG(); check_for_tasks(cpu); @@ -144,26 +269,41 @@ out_thread: err = kthread_stop(p); out_allowed: set_cpus_allowed(current, old_allowed); -out: - unlock_cpu_hotplug(); +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*/ -int __devinit cpu_up(unsigned int cpu) +/* Requires cpu_add_remove_lock to be held */ +static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) { - int ret; + int ret, nr_calls = 0; void *hcpu = (void *)(long)cpu; + unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0; - if ((ret = down_interruptible(&cpucontrol)) != 0) - return ret; + if (cpu_online(cpu) || !cpu_present(cpu)) + return -EINVAL; - if (cpu_online(cpu) || !cpu_present(cpu)) { - ret = -EINVAL; - goto out; - } - ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu); + 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; @@ -174,16 +314,102 @@ int __devinit cpu_up(unsigned int cpu) ret = __cpu_up(cpu); if (ret != 0) goto out_notify; - if (!cpu_online(cpu)) - BUG(); + BUG_ON(!cpu_online(cpu)); /* Now call notifier in preparation. */ - notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); + raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu); out_notify: if (ret != 0) - notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu); -out: - up(&cpucontrol); + __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 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 */