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(cpu_add_remove_lock); 20 static DEFINE_MUTEX(cpu_bitmask_lock); 21 22 static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain); 23 24 #ifdef CONFIG_HOTPLUG_CPU 25 26 /* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */ 27 static struct task_struct *recursive; 28 static int recursive_depth; 29 30 void lock_cpu_hotplug(void) 31 { 32 struct task_struct *tsk = current; 33 34 if (tsk == recursive) { 35 static int warnings = 10; 36 if (warnings) { 37 printk(KERN_ERR "Lukewarm IQ detected in hotplug locking\n"); 38 WARN_ON(1); 39 warnings--; 40 } 41 recursive_depth++; 42 return; 43 } 44 mutex_lock(&cpu_bitmask_lock); 45 recursive = tsk; 46 } 47 EXPORT_SYMBOL_GPL(lock_cpu_hotplug); 48 49 void unlock_cpu_hotplug(void) 50 { 51 WARN_ON(recursive != current); 52 if (recursive_depth) { 53 recursive_depth--; 54 return; 55 } 56 mutex_unlock(&cpu_bitmask_lock); 57 recursive = NULL; 58 } 59 EXPORT_SYMBOL_GPL(unlock_cpu_hotplug); 60 61 #endif /* CONFIG_HOTPLUG_CPU */ 62 63 /* Need to know about CPUs going up/down? */ 64 int __cpuinit register_cpu_notifier(struct notifier_block *nb) 65 { 66 return blocking_notifier_chain_register(&cpu_chain, nb); 67 } 68 69 #ifdef CONFIG_HOTPLUG_CPU 70 71 EXPORT_SYMBOL(register_cpu_notifier); 72 73 void unregister_cpu_notifier(struct notifier_block *nb) 74 { 75 blocking_notifier_chain_unregister(&cpu_chain, nb); 76 } 77 EXPORT_SYMBOL(unregister_cpu_notifier); 78 79 static inline void check_for_tasks(int cpu) 80 { 81 struct task_struct *p; 82 83 write_lock_irq(&tasklist_lock); 84 for_each_process(p) { 85 if (task_cpu(p) == cpu && 86 (!cputime_eq(p->utime, cputime_zero) || 87 !cputime_eq(p->stime, cputime_zero))) 88 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\ 89 (state = %ld, flags = %lx) \n", 90 p->comm, p->pid, cpu, p->state, p->flags); 91 } 92 write_unlock_irq(&tasklist_lock); 93 } 94 95 /* Take this CPU down. */ 96 static int take_cpu_down(void *unused) 97 { 98 int err; 99 100 /* Ensure this CPU doesn't handle any more interrupts. */ 101 err = __cpu_disable(); 102 if (err < 0) 103 return err; 104 105 /* Force idle task to run as soon as we yield: it should 106 immediately notice cpu is offline and die quickly. */ 107 sched_idle_next(); 108 return 0; 109 } 110 111 int cpu_down(unsigned int cpu) 112 { 113 int err; 114 struct task_struct *p; 115 cpumask_t old_allowed, tmp; 116 117 mutex_lock(&cpu_add_remove_lock); 118 if (num_online_cpus() == 1) { 119 err = -EBUSY; 120 goto out; 121 } 122 123 if (!cpu_online(cpu)) { 124 err = -EINVAL; 125 goto out; 126 } 127 128 err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, 129 (void *)(long)cpu); 130 if (err == NOTIFY_BAD) { 131 printk("%s: attempt to take down CPU %u failed\n", 132 __FUNCTION__, cpu); 133 err = -EINVAL; 134 goto out; 135 } 136 137 /* Ensure that we are not runnable on dying cpu */ 138 old_allowed = current->cpus_allowed; 139 tmp = CPU_MASK_ALL; 140 cpu_clear(cpu, tmp); 141 set_cpus_allowed(current, tmp); 142 143 mutex_lock(&cpu_bitmask_lock); 144 p = __stop_machine_run(take_cpu_down, NULL, cpu); 145 mutex_unlock(&cpu_bitmask_lock); 146 147 if (IS_ERR(p)) { 148 /* CPU didn't die: tell everyone. Can't complain. */ 149 if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, 150 (void *)(long)cpu) == NOTIFY_BAD) 151 BUG(); 152 153 err = PTR_ERR(p); 154 goto out_allowed; 155 } 156 157 if (cpu_online(cpu)) 158 goto out_thread; 159 160 /* Wait for it to sleep (leaving idle task). */ 161 while (!idle_cpu(cpu)) 162 yield(); 163 164 /* This actually kills the CPU. */ 165 __cpu_die(cpu); 166 167 /* Move it here so it can run. */ 168 kthread_bind(p, get_cpu()); 169 put_cpu(); 170 171 /* CPU is completely dead: tell everyone. Too late to complain. */ 172 if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD, 173 (void *)(long)cpu) == NOTIFY_BAD) 174 BUG(); 175 176 check_for_tasks(cpu); 177 178 out_thread: 179 err = kthread_stop(p); 180 out_allowed: 181 set_cpus_allowed(current, old_allowed); 182 out: 183 mutex_unlock(&cpu_add_remove_lock); 184 return err; 185 } 186 #endif /*CONFIG_HOTPLUG_CPU*/ 187 188 int __devinit cpu_up(unsigned int cpu) 189 { 190 int ret; 191 void *hcpu = (void *)(long)cpu; 192 193 mutex_lock(&cpu_add_remove_lock); 194 if (cpu_online(cpu) || !cpu_present(cpu)) { 195 ret = -EINVAL; 196 goto out; 197 } 198 199 ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu); 200 if (ret == NOTIFY_BAD) { 201 printk("%s: attempt to bring up CPU %u failed\n", 202 __FUNCTION__, cpu); 203 ret = -EINVAL; 204 goto out_notify; 205 } 206 207 /* Arch-specific enabling code. */ 208 mutex_lock(&cpu_bitmask_lock); 209 ret = __cpu_up(cpu); 210 mutex_unlock(&cpu_bitmask_lock); 211 if (ret != 0) 212 goto out_notify; 213 BUG_ON(!cpu_online(cpu)); 214 215 /* Now call notifier in preparation. */ 216 blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); 217 218 out_notify: 219 if (ret != 0) 220 blocking_notifier_call_chain(&cpu_chain, 221 CPU_UP_CANCELED, hcpu); 222 out: 223 mutex_unlock(&cpu_add_remove_lock); 224 return ret; 225 } 226