| 1 | /* Kernel thread helper functions. |
| 2 | * Copyright (C) 2004 IBM Corporation, Rusty Russell. |
| 3 | * |
| 4 | * Creation is done via kthreadd, so that we get a clean environment |
| 5 | * even if we're invoked from userspace (think modprobe, hotplug cpu, |
| 6 | * etc.). |
| 7 | */ |
| 8 | #include <linux/sched.h> |
| 9 | #include <linux/kthread.h> |
| 10 | #include <linux/completion.h> |
| 11 | #include <linux/err.h> |
| 12 | #include <linux/unistd.h> |
| 13 | #include <linux/file.h> |
| 14 | #include <linux/module.h> |
| 15 | #include <linux/mutex.h> |
| 16 | #include <trace/sched.h> |
| 17 | |
| 18 | #define KTHREAD_NICE_LEVEL (-5) |
| 19 | |
| 20 | static DEFINE_SPINLOCK(kthread_create_lock); |
| 21 | static LIST_HEAD(kthread_create_list); |
| 22 | struct task_struct *kthreadd_task; |
| 23 | |
| 24 | DEFINE_TRACE(sched_kthread_stop); |
| 25 | DEFINE_TRACE(sched_kthread_stop_ret); |
| 26 | |
| 27 | struct kthread_create_info |
| 28 | { |
| 29 | /* Information passed to kthread() from kthreadd. */ |
| 30 | int (*threadfn)(void *data); |
| 31 | void *data; |
| 32 | struct completion started; |
| 33 | |
| 34 | /* Result passed back to kthread_create() from kthreadd. */ |
| 35 | struct task_struct *result; |
| 36 | struct completion done; |
| 37 | |
| 38 | struct list_head list; |
| 39 | }; |
| 40 | |
| 41 | struct kthread_stop_info |
| 42 | { |
| 43 | struct task_struct *k; |
| 44 | int err; |
| 45 | struct completion done; |
| 46 | }; |
| 47 | |
| 48 | /* Thread stopping is done by setthing this var: lock serializes |
| 49 | * multiple kthread_stop calls. */ |
| 50 | static DEFINE_MUTEX(kthread_stop_lock); |
| 51 | static struct kthread_stop_info kthread_stop_info; |
| 52 | |
| 53 | /** |
| 54 | * kthread_should_stop - should this kthread return now? |
| 55 | * |
| 56 | * When someone calls kthread_stop() on your kthread, it will be woken |
| 57 | * and this will return true. You should then return, and your return |
| 58 | * value will be passed through to kthread_stop(). |
| 59 | */ |
| 60 | int kthread_should_stop(void) |
| 61 | { |
| 62 | return (kthread_stop_info.k == current); |
| 63 | } |
| 64 | EXPORT_SYMBOL(kthread_should_stop); |
| 65 | |
| 66 | static int kthread(void *_create) |
| 67 | { |
| 68 | struct kthread_create_info *create = _create; |
| 69 | int (*threadfn)(void *data); |
| 70 | void *data; |
| 71 | int ret = -EINTR; |
| 72 | |
| 73 | /* Copy data: it's on kthread's stack */ |
| 74 | threadfn = create->threadfn; |
| 75 | data = create->data; |
| 76 | |
| 77 | /* OK, tell user we're spawned, wait for stop or wakeup */ |
| 78 | __set_current_state(TASK_UNINTERRUPTIBLE); |
| 79 | create->result = current; |
| 80 | complete(&create->started); |
| 81 | schedule(); |
| 82 | |
| 83 | if (!kthread_should_stop()) |
| 84 | ret = threadfn(data); |
| 85 | |
| 86 | /* It might have exited on its own, w/o kthread_stop. Check. */ |
| 87 | if (kthread_should_stop()) { |
| 88 | kthread_stop_info.err = ret; |
| 89 | complete(&kthread_stop_info.done); |
| 90 | } |
| 91 | return 0; |
| 92 | } |
| 93 | |
| 94 | static void create_kthread(struct kthread_create_info *create) |
| 95 | { |
| 96 | int pid; |
| 97 | |
| 98 | /* We want our own signal handler (we take no signals by default). */ |
| 99 | pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD); |
| 100 | if (pid < 0) |
| 101 | create->result = ERR_PTR(pid); |
| 102 | else |
| 103 | wait_for_completion(&create->started); |
| 104 | complete(&create->done); |
| 105 | } |
| 106 | |
| 107 | /** |
| 108 | * kthread_create - create a kthread. |
| 109 | * @threadfn: the function to run until signal_pending(current). |
| 110 | * @data: data ptr for @threadfn. |
| 111 | * @namefmt: printf-style name for the thread. |
| 112 | * |
| 113 | * Description: This helper function creates and names a kernel |
| 114 | * thread. The thread will be stopped: use wake_up_process() to start |
| 115 | * it. See also kthread_run(), kthread_create_on_cpu(). |
| 116 | * |
| 117 | * When woken, the thread will run @threadfn() with @data as its |
| 118 | * argument. @threadfn() can either call do_exit() directly if it is a |
| 119 | * standalone thread for which noone will call kthread_stop(), or |
| 120 | * return when 'kthread_should_stop()' is true (which means |
| 121 | * kthread_stop() has been called). The return value should be zero |
| 122 | * or a negative error number; it will be passed to kthread_stop(). |
| 123 | * |
| 124 | * Returns a task_struct or ERR_PTR(-ENOMEM). |
| 125 | */ |
| 126 | struct task_struct *kthread_create(int (*threadfn)(void *data), |
| 127 | void *data, |
| 128 | const char namefmt[], |
| 129 | ...) |
| 130 | { |
| 131 | struct kthread_create_info create; |
| 132 | |
| 133 | create.threadfn = threadfn; |
| 134 | create.data = data; |
| 135 | init_completion(&create.started); |
| 136 | init_completion(&create.done); |
| 137 | |
| 138 | spin_lock(&kthread_create_lock); |
| 139 | list_add_tail(&create.list, &kthread_create_list); |
| 140 | spin_unlock(&kthread_create_lock); |
| 141 | |
| 142 | wake_up_process(kthreadd_task); |
| 143 | wait_for_completion(&create.done); |
| 144 | |
| 145 | if (!IS_ERR(create.result)) { |
| 146 | struct sched_param param = { .sched_priority = 0 }; |
| 147 | va_list args; |
| 148 | |
| 149 | va_start(args, namefmt); |
| 150 | vsnprintf(create.result->comm, sizeof(create.result->comm), |
| 151 | namefmt, args); |
| 152 | va_end(args); |
| 153 | /* |
| 154 | * root may have changed our (kthreadd's) priority or CPU mask. |
| 155 | * The kernel thread should not inherit these properties. |
| 156 | */ |
| 157 | sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m); |
| 158 | set_user_nice(create.result, KTHREAD_NICE_LEVEL); |
| 159 | set_cpus_allowed_ptr(create.result, cpu_all_mask); |
| 160 | } |
| 161 | return create.result; |
| 162 | } |
| 163 | EXPORT_SYMBOL(kthread_create); |
| 164 | |
| 165 | /** |
| 166 | * kthread_bind - bind a just-created kthread to a cpu. |
| 167 | * @k: thread created by kthread_create(). |
| 168 | * @cpu: cpu (might not be online, must be possible) for @k to run on. |
| 169 | * |
| 170 | * Description: This function is equivalent to set_cpus_allowed(), |
| 171 | * except that @cpu doesn't need to be online, and the thread must be |
| 172 | * stopped (i.e., just returned from kthread_create()). |
| 173 | */ |
| 174 | void kthread_bind(struct task_struct *k, unsigned int cpu) |
| 175 | { |
| 176 | /* Must have done schedule() in kthread() before we set_task_cpu */ |
| 177 | if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) { |
| 178 | WARN_ON(1); |
| 179 | return; |
| 180 | } |
| 181 | set_task_cpu(k, cpu); |
| 182 | k->cpus_allowed = cpumask_of_cpu(cpu); |
| 183 | k->rt.nr_cpus_allowed = 1; |
| 184 | k->flags |= PF_THREAD_BOUND; |
| 185 | } |
| 186 | EXPORT_SYMBOL(kthread_bind); |
| 187 | |
| 188 | /** |
| 189 | * kthread_stop - stop a thread created by kthread_create(). |
| 190 | * @k: thread created by kthread_create(). |
| 191 | * |
| 192 | * Sets kthread_should_stop() for @k to return true, wakes it, and |
| 193 | * waits for it to exit. Your threadfn() must not call do_exit() |
| 194 | * itself if you use this function! This can also be called after |
| 195 | * kthread_create() instead of calling wake_up_process(): the thread |
| 196 | * will exit without calling threadfn(). |
| 197 | * |
| 198 | * Returns the result of threadfn(), or %-EINTR if wake_up_process() |
| 199 | * was never called. |
| 200 | */ |
| 201 | int kthread_stop(struct task_struct *k) |
| 202 | { |
| 203 | int ret; |
| 204 | |
| 205 | mutex_lock(&kthread_stop_lock); |
| 206 | |
| 207 | /* It could exit after stop_info.k set, but before wake_up_process. */ |
| 208 | get_task_struct(k); |
| 209 | |
| 210 | trace_sched_kthread_stop(k); |
| 211 | |
| 212 | /* Must init completion *before* thread sees kthread_stop_info.k */ |
| 213 | init_completion(&kthread_stop_info.done); |
| 214 | smp_wmb(); |
| 215 | |
| 216 | /* Now set kthread_should_stop() to true, and wake it up. */ |
| 217 | kthread_stop_info.k = k; |
| 218 | wake_up_process(k); |
| 219 | put_task_struct(k); |
| 220 | |
| 221 | /* Once it dies, reset stop ptr, gather result and we're done. */ |
| 222 | wait_for_completion(&kthread_stop_info.done); |
| 223 | kthread_stop_info.k = NULL; |
| 224 | ret = kthread_stop_info.err; |
| 225 | mutex_unlock(&kthread_stop_lock); |
| 226 | |
| 227 | trace_sched_kthread_stop_ret(ret); |
| 228 | |
| 229 | return ret; |
| 230 | } |
| 231 | EXPORT_SYMBOL(kthread_stop); |
| 232 | |
| 233 | int kthreadd(void *unused) |
| 234 | { |
| 235 | struct task_struct *tsk = current; |
| 236 | |
| 237 | /* Setup a clean context for our children to inherit. */ |
| 238 | set_task_comm(tsk, "kthreadd"); |
| 239 | ignore_signals(tsk); |
| 240 | set_user_nice(tsk, KTHREAD_NICE_LEVEL); |
| 241 | set_cpus_allowed_ptr(tsk, cpu_all_mask); |
| 242 | |
| 243 | current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG; |
| 244 | |
| 245 | for (;;) { |
| 246 | set_current_state(TASK_INTERRUPTIBLE); |
| 247 | if (list_empty(&kthread_create_list)) |
| 248 | schedule(); |
| 249 | __set_current_state(TASK_RUNNING); |
| 250 | |
| 251 | spin_lock(&kthread_create_lock); |
| 252 | while (!list_empty(&kthread_create_list)) { |
| 253 | struct kthread_create_info *create; |
| 254 | |
| 255 | create = list_entry(kthread_create_list.next, |
| 256 | struct kthread_create_info, list); |
| 257 | list_del_init(&create->list); |
| 258 | spin_unlock(&kthread_create_lock); |
| 259 | |
| 260 | create_kthread(create); |
| 261 | |
| 262 | spin_lock(&kthread_create_lock); |
| 263 | } |
| 264 | spin_unlock(&kthread_create_lock); |
| 265 | } |
| 266 | |
| 267 | return 0; |
| 268 | } |