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 21 static struct notifier_block *cpu_chain; 22 23 /* Need to know about CPUs going up/down? */ 24 int register_cpu_notifier(struct notifier_block *nb) 25 { 26 int ret; 27 28 if ((ret = down_interruptible(&cpucontrol)) != 0) 29 return ret; 30 ret = notifier_chain_register(&cpu_chain, nb); 31 up(&cpucontrol); 32 return ret; 33 } 34 EXPORT_SYMBOL(register_cpu_notifier); 35 36 void unregister_cpu_notifier(struct notifier_block *nb) 37 { 38 down(&cpucontrol); 39 notifier_chain_unregister(&cpu_chain, nb); 40 up(&cpucontrol); 41 } 42 EXPORT_SYMBOL(unregister_cpu_notifier); 43 44 #ifdef CONFIG_HOTPLUG_CPU 45 static inline void check_for_tasks(int cpu) 46 { 47 struct task_struct *p; 48 49 write_lock_irq(&tasklist_lock); 50 for_each_process(p) { 51 if (task_cpu(p) == cpu && 52 (!cputime_eq(p->utime, cputime_zero) || 53 !cputime_eq(p->stime, cputime_zero))) 54 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\ 55 (state = %ld, flags = %lx) \n", 56 p->comm, p->pid, cpu, p->state, p->flags); 57 } 58 write_unlock_irq(&tasklist_lock); 59 } 60 61 /* Take this CPU down. */ 62 static int take_cpu_down(void *unused) 63 { 64 int err; 65 66 /* Ensure this CPU doesn't handle any more interrupts. */ 67 err = __cpu_disable(); 68 if (err < 0) 69 return err; 70 71 /* Force idle task to run as soon as we yield: it should 72 immediately notice cpu is offline and die quickly. */ 73 sched_idle_next(); 74 return 0; 75 } 76 77 int cpu_down(unsigned int cpu) 78 { 79 int err; 80 struct task_struct *p; 81 cpumask_t old_allowed, tmp; 82 83 if ((err = lock_cpu_hotplug_interruptible()) != 0) 84 return err; 85 86 if (num_online_cpus() == 1) { 87 err = -EBUSY; 88 goto out; 89 } 90 91 if (!cpu_online(cpu)) { 92 err = -EINVAL; 93 goto out; 94 } 95 96 err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, 97 (void *)(long)cpu); 98 if (err == NOTIFY_BAD) { 99 printk("%s: attempt to take down CPU %u failed\n", 100 __FUNCTION__, cpu); 101 err = -EINVAL; 102 goto out; 103 } 104 105 /* Ensure that we are not runnable on dying cpu */ 106 old_allowed = current->cpus_allowed; 107 tmp = CPU_MASK_ALL; 108 cpu_clear(cpu, tmp); 109 set_cpus_allowed(current, tmp); 110 111 p = __stop_machine_run(take_cpu_down, NULL, cpu); 112 if (IS_ERR(p)) { 113 /* CPU didn't die: tell everyone. Can't complain. */ 114 if (notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, 115 (void *)(long)cpu) == NOTIFY_BAD) 116 BUG(); 117 118 err = PTR_ERR(p); 119 goto out_allowed; 120 } 121 122 if (cpu_online(cpu)) 123 goto out_thread; 124 125 /* Wait for it to sleep (leaving idle task). */ 126 while (!idle_cpu(cpu)) 127 yield(); 128 129 /* This actually kills the CPU. */ 130 __cpu_die(cpu); 131 132 /* Move it here so it can run. */ 133 kthread_bind(p, get_cpu()); 134 put_cpu(); 135 136 /* CPU is completely dead: tell everyone. Too late to complain. */ 137 if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu) 138 == NOTIFY_BAD) 139 BUG(); 140 141 check_for_tasks(cpu); 142 143 out_thread: 144 err = kthread_stop(p); 145 out_allowed: 146 set_cpus_allowed(current, old_allowed); 147 out: 148 unlock_cpu_hotplug(); 149 return err; 150 } 151 #endif /*CONFIG_HOTPLUG_CPU*/ 152 153 int __devinit cpu_up(unsigned int cpu) 154 { 155 int ret; 156 void *hcpu = (void *)(long)cpu; 157 158 if ((ret = down_interruptible(&cpucontrol)) != 0) 159 return ret; 160 161 if (cpu_online(cpu) || !cpu_present(cpu)) { 162 ret = -EINVAL; 163 goto out; 164 } 165 ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu); 166 if (ret == NOTIFY_BAD) { 167 printk("%s: attempt to bring up CPU %u failed\n", 168 __FUNCTION__, cpu); 169 ret = -EINVAL; 170 goto out_notify; 171 } 172 173 /* Arch-specific enabling code. */ 174 ret = __cpu_up(cpu); 175 if (ret != 0) 176 goto out_notify; 177 if (!cpu_online(cpu)) 178 BUG(); 179 180 /* Now call notifier in preparation. */ 181 notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); 182 183 out_notify: 184 if (ret != 0) 185 notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu); 186 out: 187 up(&cpucontrol); 188 return ret; 189 } 190