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1da177e4 LT |
1 | /* Kernel thread helper functions. |
2 | * Copyright (C) 2004 IBM Corporation, Rusty Russell. | |
3 | * | |
73c27992 | 4 | * Creation is done via kthreadd, so that we get a clean environment |
1da177e4 LT |
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> | |
97d1f15b | 15 | #include <linux/mutex.h> |
1da177e4 LT |
16 | #include <asm/semaphore.h> |
17 | ||
73c27992 EB |
18 | static DEFINE_SPINLOCK(kthread_create_lock); |
19 | static LIST_HEAD(kthread_create_list); | |
20 | struct task_struct *kthreadd_task; | |
1da177e4 LT |
21 | |
22 | struct kthread_create_info | |
23 | { | |
73c27992 | 24 | /* Information passed to kthread() from kthreadd. */ |
1da177e4 LT |
25 | int (*threadfn)(void *data); |
26 | void *data; | |
27 | struct completion started; | |
28 | ||
73c27992 | 29 | /* Result passed back to kthread_create() from kthreadd. */ |
1da177e4 LT |
30 | struct task_struct *result; |
31 | struct completion done; | |
65f27f38 | 32 | |
73c27992 | 33 | struct list_head list; |
1da177e4 LT |
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. */ | |
97d1f15b | 45 | static DEFINE_MUTEX(kthread_stop_lock); |
1da177e4 LT |
46 | static struct kthread_stop_info kthread_stop_info; |
47 | ||
9e37bd30 RD |
48 | /** |
49 | * kthread_should_stop - should this kthread return now? | |
50 | * | |
72fd4a35 | 51 | * When someone calls kthread_stop() on your kthread, it will be woken |
9e37bd30 RD |
52 | * and this will return true. You should then return, and your return |
53 | * value will be passed through to kthread_stop(). | |
54 | */ | |
1da177e4 LT |
55 | int kthread_should_stop(void) |
56 | { | |
57 | return (kthread_stop_info.k == current); | |
58 | } | |
59 | EXPORT_SYMBOL(kthread_should_stop); | |
60 | ||
1da177e4 LT |
61 | static int kthread(void *_create) |
62 | { | |
63 | struct kthread_create_info *create = _create; | |
64 | int (*threadfn)(void *data); | |
65 | void *data; | |
1da177e4 LT |
66 | int ret = -EINTR; |
67 | ||
73c27992 | 68 | /* Copy data: it's on kthread's stack */ |
1da177e4 LT |
69 | threadfn = create->threadfn; |
70 | data = create->data; | |
71 | ||
1da177e4 | 72 | /* OK, tell user we're spawned, wait for stop or wakeup */ |
a076e4bc | 73 | __set_current_state(TASK_UNINTERRUPTIBLE); |
1da177e4 LT |
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 | ||
73c27992 | 88 | static void create_kthread(struct kthread_create_info *create) |
1da177e4 | 89 | { |
1da177e4 LT |
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); | |
05eeae20 | 98 | read_lock(&tasklist_lock); |
1da177e4 | 99 | create->result = find_task_by_pid(pid); |
05eeae20 | 100 | read_unlock(&tasklist_lock); |
1da177e4 LT |
101 | } |
102 | complete(&create->done); | |
103 | } | |
104 | ||
9e37bd30 RD |
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 | |
72fd4a35 | 116 | * argument. @threadfn() can either call do_exit() directly if it is a |
9e37bd30 RD |
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 | */ | |
1da177e4 LT |
124 | struct task_struct *kthread_create(int (*threadfn)(void *data), |
125 | void *data, | |
126 | const char namefmt[], | |
127 | ...) | |
128 | { | |
129 | struct kthread_create_info create; | |
1da177e4 LT |
130 | |
131 | create.threadfn = threadfn; | |
132 | create.data = data; | |
133 | init_completion(&create.started); | |
134 | init_completion(&create.done); | |
73c27992 EB |
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 | ||
1da177e4 LT |
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 | } | |
1da177e4 LT |
150 | return create.result; |
151 | } | |
152 | EXPORT_SYMBOL(kthread_create); | |
153 | ||
9e37bd30 RD |
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 | |
72fd4a35 | 161 | * stopped (i.e., just returned from kthread_create()). |
9e37bd30 | 162 | */ |
1da177e4 LT |
163 | void kthread_bind(struct task_struct *k, unsigned int cpu) |
164 | { | |
a076e4bc ON |
165 | if (k->state != TASK_UNINTERRUPTIBLE) { |
166 | WARN_ON(1); | |
167 | return; | |
168 | } | |
1da177e4 LT |
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 | } | |
174 | EXPORT_SYMBOL(kthread_bind); | |
175 | ||
9e37bd30 RD |
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 | */ | |
1da177e4 LT |
189 | int kthread_stop(struct task_struct *k) |
190 | { | |
191 | int ret; | |
192 | ||
97d1f15b | 193 | mutex_lock(&kthread_stop_lock); |
1da177e4 LT |
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); | |
d59dd462 | 200 | smp_wmb(); |
1da177e4 LT |
201 | |
202 | /* Now set kthread_should_stop() to true, and wake it up. */ | |
203 | kthread_stop_info.k = k; | |
52e92e57 | 204 | wake_up_process(k); |
1da177e4 LT |
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; | |
97d1f15b | 211 | mutex_unlock(&kthread_stop_lock); |
1da177e4 LT |
212 | |
213 | return ret; | |
214 | } | |
52e92e57 | 215 | EXPORT_SYMBOL(kthread_stop); |
1da177e4 | 216 | |
73c27992 | 217 | |
98011f56 | 218 | static noinline __init_refok void kthreadd_setup(void) |
1da177e4 | 219 | { |
73c27992 | 220 | struct task_struct *tsk = current; |
1da177e4 | 221 | |
73c27992 EB |
222 | set_task_comm(tsk, "kthreadd"); |
223 | ||
10ab825b | 224 | ignore_signals(tsk); |
73c27992 | 225 | |
10ab825b ON |
226 | set_user_nice(tsk, -5); |
227 | set_cpus_allowed(tsk, CPU_MASK_ALL); | |
1da177e4 | 228 | } |
1da177e4 | 229 | |
73c27992 EB |
230 | int 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 | } |