| 1 | /* CPU control. |
| 2 | * (C) 2001, 2002, 2003, 2004 Rusty Russell |
| 3 | * |
| 4 | * This code is licenced under the GPL. |
| 5 | */ |
| 6 | #include <linux/proc_fs.h> |
| 7 | #include <linux/smp.h> |
| 8 | #include <linux/init.h> |
| 9 | #include <linux/notifier.h> |
| 10 | #include <linux/sched.h> |
| 11 | #include <linux/unistd.h> |
| 12 | #include <linux/cpu.h> |
| 13 | #include <linux/module.h> |
| 14 | #include <linux/kthread.h> |
| 15 | #include <linux/stop_machine.h> |
| 16 | #include <asm/semaphore.h> |
| 17 | |
| 18 | /* This protects CPUs going up and down... */ |
| 19 | DECLARE_MUTEX(cpucontrol); |
| 20 | EXPORT_SYMBOL_GPL(cpucontrol); |
| 21 | |
| 22 | static struct notifier_block *cpu_chain; |
| 23 | |
| 24 | /* |
| 25 | * Used to check by callers if they need to acquire the cpucontrol |
| 26 | * or not to protect a cpu from being removed. Its sometimes required to |
| 27 | * call these functions both for normal operations, and in response to |
| 28 | * a cpu being added/removed. If the context of the call is in the same |
| 29 | * thread context as a CPU hotplug thread, we dont need to take the lock |
| 30 | * since its already protected |
| 31 | * check drivers/cpufreq/cpufreq.c for its usage - Ashok Raj |
| 32 | */ |
| 33 | |
| 34 | int current_in_cpu_hotplug(void) |
| 35 | { |
| 36 | return (current->flags & PF_HOTPLUG_CPU); |
| 37 | } |
| 38 | |
| 39 | EXPORT_SYMBOL_GPL(current_in_cpu_hotplug); |
| 40 | |
| 41 | |
| 42 | /* Need to know about CPUs going up/down? */ |
| 43 | int register_cpu_notifier(struct notifier_block *nb) |
| 44 | { |
| 45 | int ret; |
| 46 | |
| 47 | if ((ret = down_interruptible(&cpucontrol)) != 0) |
| 48 | return ret; |
| 49 | ret = notifier_chain_register(&cpu_chain, nb); |
| 50 | up(&cpucontrol); |
| 51 | return ret; |
| 52 | } |
| 53 | EXPORT_SYMBOL(register_cpu_notifier); |
| 54 | |
| 55 | void unregister_cpu_notifier(struct notifier_block *nb) |
| 56 | { |
| 57 | down(&cpucontrol); |
| 58 | notifier_chain_unregister(&cpu_chain, nb); |
| 59 | up(&cpucontrol); |
| 60 | } |
| 61 | EXPORT_SYMBOL(unregister_cpu_notifier); |
| 62 | |
| 63 | #ifdef CONFIG_HOTPLUG_CPU |
| 64 | static inline void check_for_tasks(int cpu) |
| 65 | { |
| 66 | struct task_struct *p; |
| 67 | |
| 68 | write_lock_irq(&tasklist_lock); |
| 69 | for_each_process(p) { |
| 70 | if (task_cpu(p) == cpu && |
| 71 | (!cputime_eq(p->utime, cputime_zero) || |
| 72 | !cputime_eq(p->stime, cputime_zero))) |
| 73 | printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\ |
| 74 | (state = %ld, flags = %lx) \n", |
| 75 | p->comm, p->pid, cpu, p->state, p->flags); |
| 76 | } |
| 77 | write_unlock_irq(&tasklist_lock); |
| 78 | } |
| 79 | |
| 80 | /* Take this CPU down. */ |
| 81 | static int take_cpu_down(void *unused) |
| 82 | { |
| 83 | int err; |
| 84 | |
| 85 | /* Ensure this CPU doesn't handle any more interrupts. */ |
| 86 | err = __cpu_disable(); |
| 87 | if (err < 0) |
| 88 | return err; |
| 89 | |
| 90 | /* Force idle task to run as soon as we yield: it should |
| 91 | immediately notice cpu is offline and die quickly. */ |
| 92 | sched_idle_next(); |
| 93 | return 0; |
| 94 | } |
| 95 | |
| 96 | int cpu_down(unsigned int cpu) |
| 97 | { |
| 98 | int err; |
| 99 | struct task_struct *p; |
| 100 | cpumask_t old_allowed, tmp; |
| 101 | |
| 102 | if ((err = lock_cpu_hotplug_interruptible()) != 0) |
| 103 | return err; |
| 104 | |
| 105 | if (num_online_cpus() == 1) { |
| 106 | err = -EBUSY; |
| 107 | goto out; |
| 108 | } |
| 109 | |
| 110 | if (!cpu_online(cpu)) { |
| 111 | err = -EINVAL; |
| 112 | goto out; |
| 113 | } |
| 114 | |
| 115 | /* |
| 116 | * Leave a trace in current->flags indicating we are already in |
| 117 | * process of performing CPU hotplug. Callers can check if cpucontrol |
| 118 | * is already acquired by current thread, and if so not cause |
| 119 | * a dead lock by not acquiring the lock |
| 120 | */ |
| 121 | current->flags |= PF_HOTPLUG_CPU; |
| 122 | err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, |
| 123 | (void *)(long)cpu); |
| 124 | if (err == NOTIFY_BAD) { |
| 125 | printk("%s: attempt to take down CPU %u failed\n", |
| 126 | __FUNCTION__, cpu); |
| 127 | err = -EINVAL; |
| 128 | goto out; |
| 129 | } |
| 130 | |
| 131 | /* Ensure that we are not runnable on dying cpu */ |
| 132 | old_allowed = current->cpus_allowed; |
| 133 | tmp = CPU_MASK_ALL; |
| 134 | cpu_clear(cpu, tmp); |
| 135 | set_cpus_allowed(current, tmp); |
| 136 | |
| 137 | p = __stop_machine_run(take_cpu_down, NULL, cpu); |
| 138 | if (IS_ERR(p)) { |
| 139 | /* CPU didn't die: tell everyone. Can't complain. */ |
| 140 | if (notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, |
| 141 | (void *)(long)cpu) == NOTIFY_BAD) |
| 142 | BUG(); |
| 143 | |
| 144 | err = PTR_ERR(p); |
| 145 | goto out_allowed; |
| 146 | } |
| 147 | |
| 148 | if (cpu_online(cpu)) |
| 149 | goto out_thread; |
| 150 | |
| 151 | /* Wait for it to sleep (leaving idle task). */ |
| 152 | while (!idle_cpu(cpu)) |
| 153 | yield(); |
| 154 | |
| 155 | /* This actually kills the CPU. */ |
| 156 | __cpu_die(cpu); |
| 157 | |
| 158 | /* Move it here so it can run. */ |
| 159 | kthread_bind(p, get_cpu()); |
| 160 | put_cpu(); |
| 161 | |
| 162 | /* CPU is completely dead: tell everyone. Too late to complain. */ |
| 163 | if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu) |
| 164 | == NOTIFY_BAD) |
| 165 | BUG(); |
| 166 | |
| 167 | check_for_tasks(cpu); |
| 168 | |
| 169 | out_thread: |
| 170 | err = kthread_stop(p); |
| 171 | out_allowed: |
| 172 | set_cpus_allowed(current, old_allowed); |
| 173 | out: |
| 174 | current->flags &= ~PF_HOTPLUG_CPU; |
| 175 | unlock_cpu_hotplug(); |
| 176 | return err; |
| 177 | } |
| 178 | #endif /*CONFIG_HOTPLUG_CPU*/ |
| 179 | |
| 180 | int __devinit cpu_up(unsigned int cpu) |
| 181 | { |
| 182 | int ret; |
| 183 | void *hcpu = (void *)(long)cpu; |
| 184 | |
| 185 | if ((ret = down_interruptible(&cpucontrol)) != 0) |
| 186 | return ret; |
| 187 | |
| 188 | if (cpu_online(cpu) || !cpu_present(cpu)) { |
| 189 | ret = -EINVAL; |
| 190 | goto out; |
| 191 | } |
| 192 | |
| 193 | /* |
| 194 | * Leave a trace in current->flags indicating we are already in |
| 195 | * process of performing CPU hotplug. |
| 196 | */ |
| 197 | current->flags |= PF_HOTPLUG_CPU; |
| 198 | ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu); |
| 199 | if (ret == NOTIFY_BAD) { |
| 200 | printk("%s: attempt to bring up CPU %u failed\n", |
| 201 | __FUNCTION__, cpu); |
| 202 | ret = -EINVAL; |
| 203 | goto out_notify; |
| 204 | } |
| 205 | |
| 206 | /* Arch-specific enabling code. */ |
| 207 | ret = __cpu_up(cpu); |
| 208 | if (ret != 0) |
| 209 | goto out_notify; |
| 210 | if (!cpu_online(cpu)) |
| 211 | BUG(); |
| 212 | |
| 213 | /* Now call notifier in preparation. */ |
| 214 | notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); |
| 215 | |
| 216 | out_notify: |
| 217 | if (ret != 0) |
| 218 | notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu); |
| 219 | out: |
| 220 | current->flags &= ~PF_HOTPLUG_CPU; |
| 221 | up(&cpucontrol); |
| 222 | return ret; |
| 223 | } |