/* 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 <asm/semaphore.h> /* This protects CPUs going up and down... */ DECLARE_MUTEX(cpucontrol); EXPORT_SYMBOL_GPL(cpucontrol); static struct notifier_block *cpu_chain; /* * Used to check by callers if they need to acquire the cpucontrol * or not to protect a cpu from being removed. Its sometimes required to * call these functions both for normal operations, and in response to * a cpu being added/removed. If the context of the call is in the same * thread context as a CPU hotplug thread, we dont need to take the lock * since its already protected * check drivers/cpufreq/cpufreq.c for its usage - Ashok Raj */ int current_in_cpu_hotplug(void) { return (current->flags & PF_HOTPLUG_CPU); } EXPORT_SYMBOL_GPL(current_in_cpu_hotplug); /* Need to know about CPUs going up/down? */ int 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); return ret; } EXPORT_SYMBOL(register_cpu_notifier); void unregister_cpu_notifier(struct notifier_block *nb) { down(&cpucontrol); notifier_chain_unregister(&cpu_chain, nb); up(&cpucontrol); } EXPORT_SYMBOL(unregister_cpu_notifier); #ifdef CONFIG_HOTPLUG_CPU 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; } int cpu_down(unsigned int cpu) { int err; struct task_struct *p; cpumask_t old_allowed, tmp; if ((err = lock_cpu_hotplug_interruptible()) != 0) return err; if (num_online_cpus() == 1) { err = -EBUSY; goto out; } if (!cpu_online(cpu)) { err = -EINVAL; goto out; } /* * Leave a trace in current->flags indicating we are already in * process of performing CPU hotplug. Callers can check if cpucontrol * is already acquired by current thread, and if so not cause * a dead lock by not acquiring the lock */ current->flags |= PF_HOTPLUG_CPU; err = 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); err = -EINVAL; goto out; } /* 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); p = __stop_machine_run(take_cpu_down, NULL, cpu); if (IS_ERR(p)) { /* CPU didn't die: tell everyone. Can't complain. */ if (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 (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); out: current->flags &= ~PF_HOTPLUG_CPU; unlock_cpu_hotplug(); return err; } #endif /*CONFIG_HOTPLUG_CPU*/ int __devinit cpu_up(unsigned int cpu) { int ret; void *hcpu = (void *)(long)cpu; if ((ret = down_interruptible(&cpucontrol)) != 0) return ret; if (cpu_online(cpu) || !cpu_present(cpu)) { ret = -EINVAL; goto out; } /* * Leave a trace in current->flags indicating we are already in * process of performing CPU hotplug. */ current->flags |= PF_HOTPLUG_CPU; ret = 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. */ ret = __cpu_up(cpu); if (ret != 0) goto out_notify; if (!cpu_online(cpu)) BUG(); /* Now call notifier in preparation. */ notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); out_notify: if (ret != 0) notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu); out: current->flags &= ~PF_HOTPLUG_CPU; up(&cpucontrol); return ret; }