Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* Kernel thread helper functions. |
| 2 | * Copyright (C) 2004 IBM Corporation, Rusty Russell. |
| 3 | * |
| 4 | * Creation is done via keventd, 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> |
Arjan van de Ven | 97d1f15 | 2006-03-23 03:00:24 -0800 | [diff] [blame] | 15 | #include <linux/mutex.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 16 | #include <asm/semaphore.h> |
| 17 | |
| 18 | /* |
| 19 | * We dont want to execute off keventd since it might |
| 20 | * hold a semaphore our callers hold too: |
| 21 | */ |
| 22 | static struct workqueue_struct *helper_wq; |
| 23 | |
| 24 | struct kthread_create_info |
| 25 | { |
| 26 | /* Information passed to kthread() from keventd. */ |
| 27 | int (*threadfn)(void *data); |
| 28 | void *data; |
| 29 | struct completion started; |
| 30 | |
| 31 | /* Result passed back to kthread_create() from keventd. */ |
| 32 | struct task_struct *result; |
| 33 | struct completion done; |
| 34 | }; |
| 35 | |
| 36 | struct kthread_stop_info |
| 37 | { |
| 38 | struct task_struct *k; |
| 39 | int err; |
| 40 | struct completion done; |
| 41 | }; |
| 42 | |
| 43 | /* Thread stopping is done by setthing this var: lock serializes |
| 44 | * multiple kthread_stop calls. */ |
Arjan van de Ven | 97d1f15 | 2006-03-23 03:00:24 -0800 | [diff] [blame] | 45 | static DEFINE_MUTEX(kthread_stop_lock); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 46 | static struct kthread_stop_info kthread_stop_info; |
| 47 | |
Randy Dunlap | 9e37bd3 | 2006-06-25 05:49:19 -0700 | [diff] [blame^] | 48 | /** |
| 49 | * kthread_should_stop - should this kthread return now? |
| 50 | * |
| 51 | * When someone calls kthread_stop on your kthread, it will be woken |
| 52 | * and this will return true. You should then return, and your return |
| 53 | * value will be passed through to kthread_stop(). |
| 54 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 55 | int kthread_should_stop(void) |
| 56 | { |
| 57 | return (kthread_stop_info.k == current); |
| 58 | } |
| 59 | EXPORT_SYMBOL(kthread_should_stop); |
| 60 | |
| 61 | static void kthread_exit_files(void) |
| 62 | { |
| 63 | struct fs_struct *fs; |
| 64 | struct task_struct *tsk = current; |
| 65 | |
| 66 | exit_fs(tsk); /* current->fs->count--; */ |
| 67 | fs = init_task.fs; |
| 68 | tsk->fs = fs; |
| 69 | atomic_inc(&fs->count); |
| 70 | exit_files(tsk); |
| 71 | current->files = init_task.files; |
| 72 | atomic_inc(&tsk->files->count); |
| 73 | } |
| 74 | |
| 75 | static int kthread(void *_create) |
| 76 | { |
| 77 | struct kthread_create_info *create = _create; |
| 78 | int (*threadfn)(void *data); |
| 79 | void *data; |
| 80 | sigset_t blocked; |
| 81 | int ret = -EINTR; |
| 82 | |
| 83 | kthread_exit_files(); |
| 84 | |
| 85 | /* Copy data: it's on keventd's stack */ |
| 86 | threadfn = create->threadfn; |
| 87 | data = create->data; |
| 88 | |
| 89 | /* Block and flush all signals (in case we're not from keventd). */ |
| 90 | sigfillset(&blocked); |
| 91 | sigprocmask(SIG_BLOCK, &blocked, NULL); |
| 92 | flush_signals(current); |
| 93 | |
| 94 | /* By default we can run anywhere, unlike keventd. */ |
| 95 | set_cpus_allowed(current, CPU_MASK_ALL); |
| 96 | |
| 97 | /* OK, tell user we're spawned, wait for stop or wakeup */ |
| 98 | __set_current_state(TASK_INTERRUPTIBLE); |
| 99 | complete(&create->started); |
| 100 | schedule(); |
| 101 | |
| 102 | if (!kthread_should_stop()) |
| 103 | ret = threadfn(data); |
| 104 | |
| 105 | /* It might have exited on its own, w/o kthread_stop. Check. */ |
| 106 | if (kthread_should_stop()) { |
| 107 | kthread_stop_info.err = ret; |
| 108 | complete(&kthread_stop_info.done); |
| 109 | } |
| 110 | return 0; |
| 111 | } |
| 112 | |
| 113 | /* We are keventd: create a thread. */ |
| 114 | static void keventd_create_kthread(void *_create) |
| 115 | { |
| 116 | struct kthread_create_info *create = _create; |
| 117 | int pid; |
| 118 | |
| 119 | /* We want our own signal handler (we take no signals by default). */ |
| 120 | pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD); |
| 121 | if (pid < 0) { |
| 122 | create->result = ERR_PTR(pid); |
| 123 | } else { |
| 124 | wait_for_completion(&create->started); |
Andrew Morton | 05eeae2 | 2006-03-25 03:07:48 -0800 | [diff] [blame] | 125 | read_lock(&tasklist_lock); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 126 | create->result = find_task_by_pid(pid); |
Andrew Morton | 05eeae2 | 2006-03-25 03:07:48 -0800 | [diff] [blame] | 127 | read_unlock(&tasklist_lock); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 128 | } |
| 129 | complete(&create->done); |
| 130 | } |
| 131 | |
Randy Dunlap | 9e37bd3 | 2006-06-25 05:49:19 -0700 | [diff] [blame^] | 132 | /** |
| 133 | * kthread_create - create a kthread. |
| 134 | * @threadfn: the function to run until signal_pending(current). |
| 135 | * @data: data ptr for @threadfn. |
| 136 | * @namefmt: printf-style name for the thread. |
| 137 | * |
| 138 | * Description: This helper function creates and names a kernel |
| 139 | * thread. The thread will be stopped: use wake_up_process() to start |
| 140 | * it. See also kthread_run(), kthread_create_on_cpu(). |
| 141 | * |
| 142 | * When woken, the thread will run @threadfn() with @data as its |
| 143 | * argument. @threadfn can either call do_exit() directly if it is a |
| 144 | * standalone thread for which noone will call kthread_stop(), or |
| 145 | * return when 'kthread_should_stop()' is true (which means |
| 146 | * kthread_stop() has been called). The return value should be zero |
| 147 | * or a negative error number; it will be passed to kthread_stop(). |
| 148 | * |
| 149 | * Returns a task_struct or ERR_PTR(-ENOMEM). |
| 150 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 151 | struct task_struct *kthread_create(int (*threadfn)(void *data), |
| 152 | void *data, |
| 153 | const char namefmt[], |
| 154 | ...) |
| 155 | { |
| 156 | struct kthread_create_info create; |
| 157 | DECLARE_WORK(work, keventd_create_kthread, &create); |
| 158 | |
| 159 | create.threadfn = threadfn; |
| 160 | create.data = data; |
| 161 | init_completion(&create.started); |
| 162 | init_completion(&create.done); |
| 163 | |
| 164 | /* |
| 165 | * The workqueue needs to start up first: |
| 166 | */ |
| 167 | if (!helper_wq) |
| 168 | work.func(work.data); |
| 169 | else { |
| 170 | queue_work(helper_wq, &work); |
| 171 | wait_for_completion(&create.done); |
| 172 | } |
| 173 | if (!IS_ERR(create.result)) { |
| 174 | va_list args; |
| 175 | va_start(args, namefmt); |
| 176 | vsnprintf(create.result->comm, sizeof(create.result->comm), |
| 177 | namefmt, args); |
| 178 | va_end(args); |
| 179 | } |
| 180 | |
| 181 | return create.result; |
| 182 | } |
| 183 | EXPORT_SYMBOL(kthread_create); |
| 184 | |
Randy Dunlap | 9e37bd3 | 2006-06-25 05:49:19 -0700 | [diff] [blame^] | 185 | /** |
| 186 | * kthread_bind - bind a just-created kthread to a cpu. |
| 187 | * @k: thread created by kthread_create(). |
| 188 | * @cpu: cpu (might not be online, must be possible) for @k to run on. |
| 189 | * |
| 190 | * Description: This function is equivalent to set_cpus_allowed(), |
| 191 | * except that @cpu doesn't need to be online, and the thread must be |
| 192 | * stopped (i.e., just returned from kthread_create(). |
| 193 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 194 | void kthread_bind(struct task_struct *k, unsigned int cpu) |
| 195 | { |
| 196 | BUG_ON(k->state != TASK_INTERRUPTIBLE); |
| 197 | /* Must have done schedule() in kthread() before we set_task_cpu */ |
| 198 | wait_task_inactive(k); |
| 199 | set_task_cpu(k, cpu); |
| 200 | k->cpus_allowed = cpumask_of_cpu(cpu); |
| 201 | } |
| 202 | EXPORT_SYMBOL(kthread_bind); |
| 203 | |
Randy Dunlap | 9e37bd3 | 2006-06-25 05:49:19 -0700 | [diff] [blame^] | 204 | /** |
| 205 | * kthread_stop - stop a thread created by kthread_create(). |
| 206 | * @k: thread created by kthread_create(). |
| 207 | * |
| 208 | * Sets kthread_should_stop() for @k to return true, wakes it, and |
| 209 | * waits for it to exit. Your threadfn() must not call do_exit() |
| 210 | * itself if you use this function! This can also be called after |
| 211 | * kthread_create() instead of calling wake_up_process(): the thread |
| 212 | * will exit without calling threadfn(). |
| 213 | * |
| 214 | * Returns the result of threadfn(), or %-EINTR if wake_up_process() |
| 215 | * was never called. |
| 216 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 217 | int kthread_stop(struct task_struct *k) |
| 218 | { |
Alan Stern | 61e1a9e | 2005-10-30 15:01:40 -0800 | [diff] [blame] | 219 | return kthread_stop_sem(k, NULL); |
| 220 | } |
| 221 | EXPORT_SYMBOL(kthread_stop); |
| 222 | |
Randy Dunlap | 9e37bd3 | 2006-06-25 05:49:19 -0700 | [diff] [blame^] | 223 | /** |
| 224 | * kthread_stop_sem - stop a thread created by kthread_create(). |
| 225 | * @k: thread created by kthread_create(). |
| 226 | * @s: semaphore that @k waits on while idle. |
| 227 | * |
| 228 | * Does essentially the same thing as kthread_stop() above, but wakes |
| 229 | * @k by calling up(@s). |
| 230 | * |
| 231 | * Returns the result of threadfn(), or %-EINTR if wake_up_process() |
| 232 | * was never called. |
| 233 | */ |
Alan Stern | 61e1a9e | 2005-10-30 15:01:40 -0800 | [diff] [blame] | 234 | int kthread_stop_sem(struct task_struct *k, struct semaphore *s) |
| 235 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 236 | int ret; |
| 237 | |
Arjan van de Ven | 97d1f15 | 2006-03-23 03:00:24 -0800 | [diff] [blame] | 238 | mutex_lock(&kthread_stop_lock); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 239 | |
| 240 | /* It could exit after stop_info.k set, but before wake_up_process. */ |
| 241 | get_task_struct(k); |
| 242 | |
| 243 | /* Must init completion *before* thread sees kthread_stop_info.k */ |
| 244 | init_completion(&kthread_stop_info.done); |
akpm@osdl.org | d59dd46 | 2005-05-01 08:58:47 -0700 | [diff] [blame] | 245 | smp_wmb(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 246 | |
| 247 | /* Now set kthread_should_stop() to true, and wake it up. */ |
| 248 | kthread_stop_info.k = k; |
Alan Stern | 61e1a9e | 2005-10-30 15:01:40 -0800 | [diff] [blame] | 249 | if (s) |
| 250 | up(s); |
| 251 | else |
| 252 | wake_up_process(k); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 253 | put_task_struct(k); |
| 254 | |
| 255 | /* Once it dies, reset stop ptr, gather result and we're done. */ |
| 256 | wait_for_completion(&kthread_stop_info.done); |
| 257 | kthread_stop_info.k = NULL; |
| 258 | ret = kthread_stop_info.err; |
Arjan van de Ven | 97d1f15 | 2006-03-23 03:00:24 -0800 | [diff] [blame] | 259 | mutex_unlock(&kthread_stop_lock); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 260 | |
| 261 | return ret; |
| 262 | } |
Alan Stern | 61e1a9e | 2005-10-30 15:01:40 -0800 | [diff] [blame] | 263 | EXPORT_SYMBOL(kthread_stop_sem); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 264 | |
| 265 | static __init int helper_init(void) |
| 266 | { |
| 267 | helper_wq = create_singlethread_workqueue("kthread"); |
| 268 | BUG_ON(!helper_wq); |
| 269 | |
| 270 | return 0; |
| 271 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 272 | |
Randy Dunlap | 9e37bd3 | 2006-06-25 05:49:19 -0700 | [diff] [blame^] | 273 | core_initcall(helper_init); |