1 /* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
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,
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 <asm/semaphore.h>
19 * We dont want to execute off keventd since it might
20 * hold a semaphore our callers hold too:
22 static struct workqueue_struct *helper_wq;
24 struct kthread_create_info
26 /* Information passed to kthread() from keventd. */
27 int (*threadfn)(void *data);
29 struct completion started;
31 /* Result passed back to kthread_create() from keventd. */
32 struct task_struct *result;
33 struct completion done;
36 struct kthread_stop_info
38 struct task_struct *k;
40 struct completion done;
43 /* Thread stopping is done by setthing this var: lock serializes
44 * multiple kthread_stop calls. */
45 static DEFINE_MUTEX(kthread_stop_lock);
46 static struct kthread_stop_info kthread_stop_info;
49 * kthread_should_stop - should this kthread return now?
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().
55 int kthread_should_stop(void)
57 return (kthread_stop_info.k == current);
59 EXPORT_SYMBOL(kthread_should_stop);
61 static void kthread_exit_files(void)
64 struct task_struct *tsk = current;
66 exit_fs(tsk); /* current->fs->count--; */
69 atomic_inc(&fs->count);
71 current->files = init_task.files;
72 atomic_inc(&tsk->files->count);
75 static int kthread(void *_create)
77 struct kthread_create_info *create = _create;
78 int (*threadfn)(void *data);
85 /* Copy data: it's on keventd's stack */
86 threadfn = create->threadfn;
89 /* Block and flush all signals (in case we're not from keventd). */
91 sigprocmask(SIG_BLOCK, &blocked, NULL);
92 flush_signals(current);
94 /* By default we can run anywhere, unlike keventd. */
95 set_cpus_allowed(current, CPU_MASK_ALL);
97 /* OK, tell user we're spawned, wait for stop or wakeup */
98 __set_current_state(TASK_INTERRUPTIBLE);
99 complete(&create->started);
102 if (!kthread_should_stop())
103 ret = threadfn(data);
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);
113 /* We are keventd: create a thread. */
114 static void keventd_create_kthread(void *_create)
116 struct kthread_create_info *create = _create;
119 /* We want our own signal handler (we take no signals by default). */
120 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
122 create->result = ERR_PTR(pid);
124 wait_for_completion(&create->started);
125 read_lock(&tasklist_lock);
126 create->result = find_task_by_pid(pid);
127 read_unlock(&tasklist_lock);
129 complete(&create->done);
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.
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().
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().
149 * Returns a task_struct or ERR_PTR(-ENOMEM).
151 struct task_struct *kthread_create(int (*threadfn)(void *data),
153 const char namefmt[],
156 struct kthread_create_info create;
157 DECLARE_WORK(work, keventd_create_kthread, &create);
159 create.threadfn = threadfn;
161 init_completion(&create.started);
162 init_completion(&create.done);
165 * The workqueue needs to start up first:
168 work.func(work.data);
170 queue_work(helper_wq, &work);
171 wait_for_completion(&create.done);
173 if (!IS_ERR(create.result)) {
175 va_start(args, namefmt);
176 vsnprintf(create.result->comm, sizeof(create.result->comm),
181 return create.result;
183 EXPORT_SYMBOL(kthread_create);
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.
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().
194 void kthread_bind(struct task_struct *k, unsigned int cpu)
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);
202 EXPORT_SYMBOL(kthread_bind);
205 * kthread_stop - stop a thread created by kthread_create().
206 * @k: thread created by kthread_create().
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().
214 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
217 int kthread_stop(struct task_struct *k)
221 mutex_lock(&kthread_stop_lock);
223 /* It could exit after stop_info.k set, but before wake_up_process. */
226 /* Must init completion *before* thread sees kthread_stop_info.k */
227 init_completion(&kthread_stop_info.done);
230 /* Now set kthread_should_stop() to true, and wake it up. */
231 kthread_stop_info.k = k;
235 /* Once it dies, reset stop ptr, gather result and we're done. */
236 wait_for_completion(&kthread_stop_info.done);
237 kthread_stop_info.k = NULL;
238 ret = kthread_stop_info.err;
239 mutex_unlock(&kthread_stop_lock);
243 EXPORT_SYMBOL(kthread_stop);
245 static __init int helper_init(void)
247 helper_wq = create_singlethread_workqueue("kthread");
253 core_initcall(helper_init);