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 /* Need to know about CPUs going up/down? */ 25 int register_cpu_notifier(struct notifier_block *nb) 26 { 27 int ret; 28 29 if ((ret = down_interruptible(&cpucontrol)) != 0) 30 return ret; 31 ret = notifier_chain_register(&cpu_chain, nb); 32 up(&cpucontrol); 33 return ret; 34 } 35 EXPORT_SYMBOL(register_cpu_notifier); 36 37 void unregister_cpu_notifier(struct notifier_block *nb) 38 { 39 down(&cpucontrol); 40 notifier_chain_unregister(&cpu_chain, nb); 41 up(&cpucontrol); 42 } 43 EXPORT_SYMBOL(unregister_cpu_notifier); 44 45 #ifdef CONFIG_HOTPLUG_CPU 46 static inline void check_for_tasks(int cpu) 47 { 48 struct task_struct *p; 49 50 write_lock_irq(&tasklist_lock); 51 for_each_process(p) { 52 if (task_cpu(p) == cpu && 53 (!cputime_eq(p->utime, cputime_zero) || 54 !cputime_eq(p->stime, cputime_zero))) 55 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\ 56 (state = %ld, flags = %lx) \n", 57 p->comm, p->pid, cpu, p->state, p->flags); 58 } 59 write_unlock_irq(&tasklist_lock); 60 } 61 62 /* Take this CPU down. */ 63 static int take_cpu_down(void *unused) 64 { 65 int err; 66 67 /* Ensure this CPU doesn't handle any more interrupts. */ 68 err = __cpu_disable(); 69 if (err < 0) 70 return err; 71 72 /* Force idle task to run as soon as we yield: it should 73 immediately notice cpu is offline and die quickly. */ 74 sched_idle_next(); 75 return 0; 76 } 77 78 int cpu_down(unsigned int cpu) 79 { 80 int err; 81 struct task_struct *p; 82 cpumask_t old_allowed, tmp; 83 84 if ((err = lock_cpu_hotplug_interruptible()) != 0) 85 return err; 86 87 if (num_online_cpus() == 1) { 88 err = -EBUSY; 89 goto out; 90 } 91 92 if (!cpu_online(cpu)) { 93 err = -EINVAL; 94 goto out; 95 } 96 97 err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, 98 (void *)(long)cpu); 99 if (err == NOTIFY_BAD) { 100 printk("%s: attempt to take down CPU %u failed\n", 101 __FUNCTION__, cpu); 102 err = -EINVAL; 103 goto out; 104 } 105 106 /* Ensure that we are not runnable on dying cpu */ 107 old_allowed = current->cpus_allowed; 108 tmp = CPU_MASK_ALL; 109 cpu_clear(cpu, tmp); 110 set_cpus_allowed(current, tmp); 111 112 p = __stop_machine_run(take_cpu_down, NULL, cpu); 113 if (IS_ERR(p)) { 114 /* CPU didn't die: tell everyone. Can't complain. */ 115 if (notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, 116 (void *)(long)cpu) == NOTIFY_BAD) 117 BUG(); 118 119 err = PTR_ERR(p); 120 goto out_allowed; 121 } 122 123 if (cpu_online(cpu)) 124 goto out_thread; 125 126 /* Wait for it to sleep (leaving idle task). */ 127 while (!idle_cpu(cpu)) 128 yield(); 129 130 /* This actually kills the CPU. */ 131 __cpu_die(cpu); 132 133 /* Move it here so it can run. */ 134 kthread_bind(p, get_cpu()); 135 put_cpu(); 136 137 /* CPU is completely dead: tell everyone. Too late to complain. */ 138 if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu) 139 == NOTIFY_BAD) 140 BUG(); 141 142 check_for_tasks(cpu); 143 144 out_thread: 145 err = kthread_stop(p); 146 out_allowed: 147 set_cpus_allowed(current, old_allowed); 148 out: 149 unlock_cpu_hotplug(); 150 return err; 151 } 152 #endif /*CONFIG_HOTPLUG_CPU*/ 153 154 int __devinit cpu_up(unsigned int cpu) 155 { 156 int ret; 157 void *hcpu = (void *)(long)cpu; 158 159 if ((ret = down_interruptible(&cpucontrol)) != 0) 160 return ret; 161 162 if (cpu_online(cpu) || !cpu_present(cpu)) { 163 ret = -EINVAL; 164 goto out; 165 } 166 ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu); 167 if (ret == NOTIFY_BAD) { 168 printk("%s: attempt to bring up CPU %u failed\n", 169 __FUNCTION__, cpu); 170 ret = -EINVAL; 171 goto out_notify; 172 } 173 174 /* Arch-specific enabling code. */ 175 ret = __cpu_up(cpu); 176 if (ret != 0) 177 goto out_notify; 178 if (!cpu_online(cpu)) 179 BUG(); 180 181 /* Now call notifier in preparation. */ 182 notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); 183 184 out_notify: 185 if (ret != 0) 186 notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu); 187 out: 188 up(&cpucontrol); 189 return ret; 190 } 191