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