projects/linux·blob v2.6.22-rc4 · refs

260 lines · 6.8 KiB

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