/* 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