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1da177e4 LT |
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> | |
97d1f15b | 15 | #include <linux/mutex.h> |
1da177e4 LT |
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. */ | |
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 | * | |
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 | */ | |
1da177e4 LT |
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); | |
05eeae20 | 125 | read_lock(&tasklist_lock); |
1da177e4 | 126 | create->result = find_task_by_pid(pid); |
05eeae20 | 127 | read_unlock(&tasklist_lock); |
1da177e4 LT |
128 | } |
129 | complete(&create->done); | |
130 | } | |
131 | ||
9e37bd30 RD |
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 | */ | |
1da177e4 LT |
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 | ||
9e37bd30 RD |
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 | */ | |
1da177e4 LT |
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 | ||
9e37bd30 RD |
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 | */ | |
1da177e4 LT |
217 | int kthread_stop(struct task_struct *k) |
218 | { | |
219 | int ret; | |
220 | ||
97d1f15b | 221 | mutex_lock(&kthread_stop_lock); |
1da177e4 LT |
222 | |
223 | /* It could exit after stop_info.k set, but before wake_up_process. */ | |
224 | get_task_struct(k); | |
225 | ||
226 | /* Must init completion *before* thread sees kthread_stop_info.k */ | |
227 | init_completion(&kthread_stop_info.done); | |
d59dd462 | 228 | smp_wmb(); |
1da177e4 LT |
229 | |
230 | /* Now set kthread_should_stop() to true, and wake it up. */ | |
231 | kthread_stop_info.k = k; | |
52e92e57 | 232 | wake_up_process(k); |
1da177e4 LT |
233 | put_task_struct(k); |
234 | ||
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; | |
97d1f15b | 239 | mutex_unlock(&kthread_stop_lock); |
1da177e4 LT |
240 | |
241 | return ret; | |
242 | } | |
52e92e57 | 243 | EXPORT_SYMBOL(kthread_stop); |
1da177e4 LT |
244 | |
245 | static __init int helper_init(void) | |
246 | { | |
247 | helper_wq = create_singlethread_workqueue("kthread"); | |
248 | BUG_ON(!helper_wq); | |
249 | ||
250 | return 0; | |
251 | } | |
1da177e4 | 252 | |
9e37bd30 | 253 | core_initcall(helper_init); |