Commit | Line | Data |
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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> |
ad8d75ff | 16 | #include <trace/events/sched.h> |
1da177e4 | 17 | |
4f05b98d MS |
18 | #define KTHREAD_NICE_LEVEL (-5) |
19 | ||
73c27992 EB |
20 | static DEFINE_SPINLOCK(kthread_create_lock); |
21 | static LIST_HEAD(kthread_create_list); | |
22 | struct task_struct *kthreadd_task; | |
1da177e4 LT |
23 | |
24 | struct kthread_create_info | |
25 | { | |
73c27992 | 26 | /* Information passed to kthread() from kthreadd. */ |
1da177e4 LT |
27 | int (*threadfn)(void *data); |
28 | void *data; | |
29 | struct completion started; | |
30 | ||
73c27992 | 31 | /* Result passed back to kthread_create() from kthreadd. */ |
1da177e4 LT |
32 | struct task_struct *result; |
33 | struct completion done; | |
65f27f38 | 34 | |
73c27992 | 35 | struct list_head list; |
1da177e4 LT |
36 | }; |
37 | ||
38 | struct 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. */ | |
97d1f15b | 47 | static DEFINE_MUTEX(kthread_stop_lock); |
1da177e4 LT |
48 | static struct kthread_stop_info kthread_stop_info; |
49 | ||
9e37bd30 RD |
50 | /** |
51 | * kthread_should_stop - should this kthread return now? | |
52 | * | |
72fd4a35 | 53 | * When someone calls kthread_stop() on your kthread, it will be woken |
9e37bd30 RD |
54 | * and this will return true. You should then return, and your return |
55 | * value will be passed through to kthread_stop(). | |
56 | */ | |
1da177e4 LT |
57 | int kthread_should_stop(void) |
58 | { | |
59 | return (kthread_stop_info.k == current); | |
60 | } | |
61 | EXPORT_SYMBOL(kthread_should_stop); | |
62 | ||
1da177e4 LT |
63 | static int kthread(void *_create) |
64 | { | |
65 | struct kthread_create_info *create = _create; | |
66 | int (*threadfn)(void *data); | |
67 | void *data; | |
1da177e4 LT |
68 | int ret = -EINTR; |
69 | ||
73c27992 | 70 | /* Copy data: it's on kthread's stack */ |
1da177e4 LT |
71 | threadfn = create->threadfn; |
72 | data = create->data; | |
73 | ||
1da177e4 | 74 | /* OK, tell user we're spawned, wait for stop or wakeup */ |
a076e4bc | 75 | __set_current_state(TASK_UNINTERRUPTIBLE); |
3217ab97 | 76 | create->result = current; |
1da177e4 LT |
77 | complete(&create->started); |
78 | schedule(); | |
79 | ||
80 | if (!kthread_should_stop()) | |
81 | ret = threadfn(data); | |
82 | ||
83 | /* It might have exited on its own, w/o kthread_stop. Check. */ | |
84 | if (kthread_should_stop()) { | |
85 | kthread_stop_info.err = ret; | |
86 | complete(&kthread_stop_info.done); | |
87 | } | |
88 | return 0; | |
89 | } | |
90 | ||
73c27992 | 91 | static void create_kthread(struct kthread_create_info *create) |
1da177e4 | 92 | { |
1da177e4 LT |
93 | int pid; |
94 | ||
95 | /* We want our own signal handler (we take no signals by default). */ | |
96 | pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD); | |
1c99315b | 97 | if (pid < 0) |
1da177e4 | 98 | create->result = ERR_PTR(pid); |
1c99315b | 99 | else |
1da177e4 | 100 | wait_for_completion(&create->started); |
1da177e4 LT |
101 | complete(&create->done); |
102 | } | |
103 | ||
9e37bd30 RD |
104 | /** |
105 | * kthread_create - create a kthread. | |
106 | * @threadfn: the function to run until signal_pending(current). | |
107 | * @data: data ptr for @threadfn. | |
108 | * @namefmt: printf-style name for the thread. | |
109 | * | |
110 | * Description: This helper function creates and names a kernel | |
111 | * thread. The thread will be stopped: use wake_up_process() to start | |
112 | * it. See also kthread_run(), kthread_create_on_cpu(). | |
113 | * | |
114 | * When woken, the thread will run @threadfn() with @data as its | |
72fd4a35 | 115 | * argument. @threadfn() can either call do_exit() directly if it is a |
9e37bd30 RD |
116 | * standalone thread for which noone will call kthread_stop(), or |
117 | * return when 'kthread_should_stop()' is true (which means | |
118 | * kthread_stop() has been called). The return value should be zero | |
119 | * or a negative error number; it will be passed to kthread_stop(). | |
120 | * | |
121 | * Returns a task_struct or ERR_PTR(-ENOMEM). | |
122 | */ | |
1da177e4 LT |
123 | struct task_struct *kthread_create(int (*threadfn)(void *data), |
124 | void *data, | |
125 | const char namefmt[], | |
126 | ...) | |
127 | { | |
128 | struct kthread_create_info create; | |
1da177e4 LT |
129 | |
130 | create.threadfn = threadfn; | |
131 | create.data = data; | |
132 | init_completion(&create.started); | |
133 | init_completion(&create.done); | |
73c27992 EB |
134 | |
135 | spin_lock(&kthread_create_lock); | |
136 | list_add_tail(&create.list, &kthread_create_list); | |
73c27992 EB |
137 | spin_unlock(&kthread_create_lock); |
138 | ||
cbd9b67b | 139 | wake_up_process(kthreadd_task); |
73c27992 EB |
140 | wait_for_completion(&create.done); |
141 | ||
1da177e4 | 142 | if (!IS_ERR(create.result)) { |
1c99315b | 143 | struct sched_param param = { .sched_priority = 0 }; |
1da177e4 | 144 | va_list args; |
1c99315b | 145 | |
1da177e4 LT |
146 | va_start(args, namefmt); |
147 | vsnprintf(create.result->comm, sizeof(create.result->comm), | |
148 | namefmt, args); | |
149 | va_end(args); | |
1c99315b ON |
150 | /* |
151 | * root may have changed our (kthreadd's) priority or CPU mask. | |
152 | * The kernel thread should not inherit these properties. | |
153 | */ | |
154 | sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m); | |
155 | set_user_nice(create.result, KTHREAD_NICE_LEVEL); | |
156 | set_cpus_allowed_ptr(create.result, cpu_all_mask); | |
1da177e4 | 157 | } |
1da177e4 LT |
158 | return create.result; |
159 | } | |
160 | EXPORT_SYMBOL(kthread_create); | |
161 | ||
9e37bd30 RD |
162 | /** |
163 | * kthread_bind - bind a just-created kthread to a cpu. | |
164 | * @k: thread created by kthread_create(). | |
165 | * @cpu: cpu (might not be online, must be possible) for @k to run on. | |
166 | * | |
167 | * Description: This function is equivalent to set_cpus_allowed(), | |
168 | * except that @cpu doesn't need to be online, and the thread must be | |
72fd4a35 | 169 | * stopped (i.e., just returned from kthread_create()). |
9e37bd30 | 170 | */ |
1da177e4 LT |
171 | void kthread_bind(struct task_struct *k, unsigned int cpu) |
172 | { | |
293adee6 ON |
173 | /* Must have done schedule() in kthread() before we set_task_cpu */ |
174 | if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) { | |
a076e4bc ON |
175 | WARN_ON(1); |
176 | return; | |
177 | } | |
1da177e4 LT |
178 | set_task_cpu(k, cpu); |
179 | k->cpus_allowed = cpumask_of_cpu(cpu); | |
9f0e738f | 180 | k->rt.nr_cpus_allowed = 1; |
9985b0ba | 181 | k->flags |= PF_THREAD_BOUND; |
1da177e4 LT |
182 | } |
183 | EXPORT_SYMBOL(kthread_bind); | |
184 | ||
9e37bd30 RD |
185 | /** |
186 | * kthread_stop - stop a thread created by kthread_create(). | |
187 | * @k: thread created by kthread_create(). | |
188 | * | |
189 | * Sets kthread_should_stop() for @k to return true, wakes it, and | |
190 | * waits for it to exit. Your threadfn() must not call do_exit() | |
191 | * itself if you use this function! This can also be called after | |
192 | * kthread_create() instead of calling wake_up_process(): the thread | |
193 | * will exit without calling threadfn(). | |
194 | * | |
195 | * Returns the result of threadfn(), or %-EINTR if wake_up_process() | |
196 | * was never called. | |
197 | */ | |
1da177e4 LT |
198 | int kthread_stop(struct task_struct *k) |
199 | { | |
200 | int ret; | |
201 | ||
97d1f15b | 202 | mutex_lock(&kthread_stop_lock); |
1da177e4 LT |
203 | |
204 | /* It could exit after stop_info.k set, but before wake_up_process. */ | |
205 | get_task_struct(k); | |
206 | ||
0a16b607 MD |
207 | trace_sched_kthread_stop(k); |
208 | ||
1da177e4 LT |
209 | /* Must init completion *before* thread sees kthread_stop_info.k */ |
210 | init_completion(&kthread_stop_info.done); | |
d59dd462 | 211 | smp_wmb(); |
1da177e4 LT |
212 | |
213 | /* Now set kthread_should_stop() to true, and wake it up. */ | |
214 | kthread_stop_info.k = k; | |
52e92e57 | 215 | wake_up_process(k); |
1da177e4 LT |
216 | put_task_struct(k); |
217 | ||
218 | /* Once it dies, reset stop ptr, gather result and we're done. */ | |
219 | wait_for_completion(&kthread_stop_info.done); | |
220 | kthread_stop_info.k = NULL; | |
221 | ret = kthread_stop_info.err; | |
97d1f15b | 222 | mutex_unlock(&kthread_stop_lock); |
1da177e4 | 223 | |
0a16b607 MD |
224 | trace_sched_kthread_stop_ret(ret); |
225 | ||
1da177e4 LT |
226 | return ret; |
227 | } | |
52e92e57 | 228 | EXPORT_SYMBOL(kthread_stop); |
1da177e4 | 229 | |
e804a4a4 | 230 | int kthreadd(void *unused) |
1da177e4 | 231 | { |
73c27992 | 232 | struct task_struct *tsk = current; |
1da177e4 | 233 | |
e804a4a4 | 234 | /* Setup a clean context for our children to inherit. */ |
73c27992 | 235 | set_task_comm(tsk, "kthreadd"); |
10ab825b | 236 | ignore_signals(tsk); |
4f05b98d | 237 | set_user_nice(tsk, KTHREAD_NICE_LEVEL); |
1a2142af | 238 | set_cpus_allowed_ptr(tsk, cpu_all_mask); |
73c27992 | 239 | |
ebb12db5 | 240 | current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG; |
73c27992 EB |
241 | |
242 | for (;;) { | |
243 | set_current_state(TASK_INTERRUPTIBLE); | |
244 | if (list_empty(&kthread_create_list)) | |
245 | schedule(); | |
246 | __set_current_state(TASK_RUNNING); | |
247 | ||
248 | spin_lock(&kthread_create_lock); | |
249 | while (!list_empty(&kthread_create_list)) { | |
250 | struct kthread_create_info *create; | |
251 | ||
252 | create = list_entry(kthread_create_list.next, | |
253 | struct kthread_create_info, list); | |
254 | list_del_init(&create->list); | |
255 | spin_unlock(&kthread_create_lock); | |
256 | ||
257 | create_kthread(create); | |
258 | ||
259 | spin_lock(&kthread_create_lock); | |
260 | } | |
261 | spin_unlock(&kthread_create_lock); | |
262 | } | |
263 | ||
264 | return 0; | |
265 | } |