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 <linux/mutex.h> 17 18 /* This protects CPUs going up and down... */ 19 static DEFINE_MUTEX(cpucontrol); 20 21 static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain); 22 23 #ifdef CONFIG_HOTPLUG_CPU 24 static struct task_struct *lock_cpu_hotplug_owner; 25 static int lock_cpu_hotplug_depth; 26 27 static int __lock_cpu_hotplug(int interruptible) 28 { 29 int ret = 0; 30 31 if (lock_cpu_hotplug_owner != current) { 32 if (interruptible) 33 ret = mutex_lock_interruptible(&cpucontrol); 34 else 35 mutex_lock(&cpucontrol); 36 } 37 38 /* 39 * Set only if we succeed in locking 40 */ 41 if (!ret) { 42 lock_cpu_hotplug_depth++; 43 lock_cpu_hotplug_owner = current; 44 } 45 46 return ret; 47 } 48 49 void lock_cpu_hotplug(void) 50 { 51 __lock_cpu_hotplug(0); 52 } 53 EXPORT_SYMBOL_GPL(lock_cpu_hotplug); 54 55 void unlock_cpu_hotplug(void) 56 { 57 if (--lock_cpu_hotplug_depth == 0) { 58 lock_cpu_hotplug_owner = NULL; 59 mutex_unlock(&cpucontrol); 60 } 61 } 62 EXPORT_SYMBOL_GPL(unlock_cpu_hotplug); 63 64 int lock_cpu_hotplug_interruptible(void) 65 { 66 return __lock_cpu_hotplug(1); 67 } 68 EXPORT_SYMBOL_GPL(lock_cpu_hotplug_interruptible); 69 #endif /* CONFIG_HOTPLUG_CPU */ 70 71 /* Need to know about CPUs going up/down? */ 72 int __cpuinit register_cpu_notifier(struct notifier_block *nb) 73 { 74 return blocking_notifier_chain_register(&cpu_chain, nb); 75 } 76 77 #ifdef CONFIG_HOTPLUG_CPU 78 79 EXPORT_SYMBOL(register_cpu_notifier); 80 81 void unregister_cpu_notifier(struct notifier_block *nb) 82 { 83 blocking_notifier_chain_unregister(&cpu_chain, nb); 84 } 85 EXPORT_SYMBOL(unregister_cpu_notifier); 86 87 static inline void check_for_tasks(int cpu) 88 { 89 struct task_struct *p; 90 91 write_lock_irq(&tasklist_lock); 92 for_each_process(p) { 93 if (task_cpu(p) == cpu && 94 (!cputime_eq(p->utime, cputime_zero) || 95 !cputime_eq(p->stime, cputime_zero))) 96 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\ 97 (state = %ld, flags = %lx) \n", 98 p->comm, p->pid, cpu, p->state, p->flags); 99 } 100 write_unlock_irq(&tasklist_lock); 101 } 102 103 /* Take this CPU down. */ 104 static int take_cpu_down(void *unused) 105 { 106 int err; 107 108 /* Ensure this CPU doesn't handle any more interrupts. */ 109 err = __cpu_disable(); 110 if (err < 0) 111 return err; 112 113 /* Force idle task to run as soon as we yield: it should 114 immediately notice cpu is offline and die quickly. */ 115 sched_idle_next(); 116 return 0; 117 } 118 119 int cpu_down(unsigned int cpu) 120 { 121 int err; 122 struct task_struct *p; 123 cpumask_t old_allowed, tmp; 124 125 if ((err = lock_cpu_hotplug_interruptible()) != 0) 126 return err; 127 128 if (num_online_cpus() == 1) { 129 err = -EBUSY; 130 goto out; 131 } 132 133 if (!cpu_online(cpu)) { 134 err = -EINVAL; 135 goto out; 136 } 137 138 err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, 139 (void *)(long)cpu); 140 if (err == NOTIFY_BAD) { 141 printk("%s: attempt to take down CPU %u failed\n", 142 __FUNCTION__, cpu); 143 err = -EINVAL; 144 goto out; 145 } 146 147 /* Ensure that we are not runnable on dying cpu */ 148 old_allowed = current->cpus_allowed; 149 tmp = CPU_MASK_ALL; 150 cpu_clear(cpu, tmp); 151 set_cpus_allowed(current, tmp); 152 153 p = __stop_machine_run(take_cpu_down, NULL, cpu); 154 if (IS_ERR(p)) { 155 /* CPU didn't die: tell everyone. Can't complain. */ 156 if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, 157 (void *)(long)cpu) == NOTIFY_BAD) 158 BUG(); 159 160 err = PTR_ERR(p); 161 goto out_allowed; 162 } 163 164 if (cpu_online(cpu)) 165 goto out_thread; 166 167 /* Wait for it to sleep (leaving idle task). */ 168 while (!idle_cpu(cpu)) 169 yield(); 170 171 /* This actually kills the CPU. */ 172 __cpu_die(cpu); 173 174 /* Move it here so it can run. */ 175 kthread_bind(p, get_cpu()); 176 put_cpu(); 177 178 /* CPU is completely dead: tell everyone. Too late to complain. */ 179 if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD, 180 (void *)(long)cpu) == NOTIFY_BAD) 181 BUG(); 182 183 check_for_tasks(cpu); 184 185 out_thread: 186 err = kthread_stop(p); 187 out_allowed: 188 set_cpus_allowed(current, old_allowed); 189 out: 190 unlock_cpu_hotplug(); 191 return err; 192 } 193 #endif /*CONFIG_HOTPLUG_CPU*/ 194 195 int __devinit cpu_up(unsigned int cpu) 196 { 197 int ret; 198 void *hcpu = (void *)(long)cpu; 199 200 if ((ret = lock_cpu_hotplug_interruptible()) != 0) 201 return ret; 202 203 if (cpu_online(cpu) || !cpu_present(cpu)) { 204 ret = -EINVAL; 205 goto out; 206 } 207 208 ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu); 209 if (ret == NOTIFY_BAD) { 210 printk("%s: attempt to bring up CPU %u failed\n", 211 __FUNCTION__, cpu); 212 ret = -EINVAL; 213 goto out_notify; 214 } 215 216 /* Arch-specific enabling code. */ 217 ret = __cpu_up(cpu); 218 if (ret != 0) 219 goto out_notify; 220 BUG_ON(!cpu_online(cpu)); 221 222 /* Now call notifier in preparation. */ 223 blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); 224 225 out_notify: 226 if (ret != 0) 227 blocking_notifier_call_chain(&cpu_chain, 228 CPU_UP_CANCELED, hcpu); 229 out: 230 unlock_cpu_hotplug(); 231 return ret; 232 } 233