projects/linux·blob v2.6.20-rc5 · refs

256 lines · 6.8 KiB

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