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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/cpuset.h> |
13 | #include <linux/unistd.h> |
14 | #include <linux/file.h> |
15 | #include <linux/module.h> |
16 | #include <linux/mutex.h> |
17 | #include <trace/events/sched.h> |
18 | |
19 | static DEFINE_SPINLOCK(kthread_create_lock); |
20 | static LIST_HEAD(kthread_create_list); |
21 | struct task_struct *kthreadd_task; |
22 | |
23 | struct kthread_create_info |
24 | { |
25 | /* Information passed to kthread() from kthreadd. */ |
26 | int (*threadfn)(void *data); |
27 | void *data; |
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 | |
36 | struct kthread { |
37 | int should_stop; |
38 | struct completion exited; |
39 | }; |
40 | |
41 | #define to_kthread(tsk) \ |
42 | container_of((tsk)->vfork_done, struct kthread, exited) |
43 | |
44 | /** |
45 | * kthread_should_stop - should this kthread return now? |
46 | * |
47 | * When someone calls kthread_stop() on your kthread, it will be woken |
48 | * and this will return true. You should then return, and your return |
49 | * value will be passed through to kthread_stop(). |
50 | */ |
51 | int kthread_should_stop(void) |
52 | { |
53 | return to_kthread(current)->should_stop; |
54 | } |
55 | EXPORT_SYMBOL(kthread_should_stop); |
56 | |
57 | static int kthread(void *_create) |
58 | { |
59 | /* Copy data: it's on kthread's stack */ |
60 | struct kthread_create_info *create = _create; |
61 | int (*threadfn)(void *data) = create->threadfn; |
62 | void *data = create->data; |
63 | struct kthread self; |
64 | int ret; |
65 | |
66 | self.should_stop = 0; |
67 | init_completion(&self.exited); |
68 | current->vfork_done = &self.exited; |
69 | |
70 | /* OK, tell user we're spawned, wait for stop or wakeup */ |
71 | __set_current_state(TASK_UNINTERRUPTIBLE); |
72 | create->result = current; |
73 | complete(&create->done); |
74 | schedule(); |
75 | |
76 | ret = -EINTR; |
77 | if (!self.should_stop) |
78 | ret = threadfn(data); |
79 | |
80 | /* we can't just return, we must preserve "self" on stack */ |
81 | do_exit(ret); |
82 | } |
83 | |
84 | static void create_kthread(struct kthread_create_info *create) |
85 | { |
86 | int pid; |
87 | |
88 | /* We want our own signal handler (we take no signals by default). */ |
89 | pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD); |
90 | if (pid < 0) { |
91 | create->result = ERR_PTR(pid); |
92 | complete(&create->done); |
93 | } |
94 | } |
95 | |
96 | /** |
97 | * kthread_create - create a kthread. |
98 | * @threadfn: the function to run until signal_pending(current). |
99 | * @data: data ptr for @threadfn. |
100 | * @namefmt: printf-style name for the thread. |
101 | * |
102 | * Description: This helper function creates and names a kernel |
103 | * thread. The thread will be stopped: use wake_up_process() to start |
104 | * it. See also kthread_run(). |
105 | * |
106 | * When woken, the thread will run @threadfn() with @data as its |
107 | * argument. @threadfn() can either call do_exit() directly if it is a |
108 | * standalone thread for which noone will call kthread_stop(), or |
109 | * return when 'kthread_should_stop()' is true (which means |
110 | * kthread_stop() has been called). The return value should be zero |
111 | * or a negative error number; it will be passed to kthread_stop(). |
112 | * |
113 | * Returns a task_struct or ERR_PTR(-ENOMEM). |
114 | */ |
115 | struct task_struct *kthread_create(int (*threadfn)(void *data), |
116 | void *data, |
117 | const char namefmt[], |
118 | ...) |
119 | { |
120 | struct kthread_create_info create; |
121 | |
122 | create.threadfn = threadfn; |
123 | create.data = data; |
124 | init_completion(&create.done); |
125 | |
126 | spin_lock(&kthread_create_lock); |
127 | list_add_tail(&create.list, &kthread_create_list); |
128 | spin_unlock(&kthread_create_lock); |
129 | |
130 | wake_up_process(kthreadd_task); |
131 | wait_for_completion(&create.done); |
132 | |
133 | if (!IS_ERR(create.result)) { |
134 | struct sched_param param = { .sched_priority = 0 }; |
135 | va_list args; |
136 | |
137 | va_start(args, namefmt); |
138 | vsnprintf(create.result->comm, sizeof(create.result->comm), |
139 | namefmt, args); |
140 | va_end(args); |
141 | /* |
142 | * root may have changed our (kthreadd's) priority or CPU mask. |
143 | * The kernel thread should not inherit these properties. |
144 | */ |
145 | sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m); |
146 | set_cpus_allowed_ptr(create.result, cpu_all_mask); |
147 | } |
148 | return create.result; |
149 | } |
150 | EXPORT_SYMBOL(kthread_create); |
151 | |
152 | /** |
153 | * kthread_bind - bind a just-created kthread to a cpu. |
154 | * @p: thread created by kthread_create(). |
155 | * @cpu: cpu (might not be online, must be possible) for @k to run on. |
156 | * |
157 | * Description: This function is equivalent to set_cpus_allowed(), |
158 | * except that @cpu doesn't need to be online, and the thread must be |
159 | * stopped (i.e., just returned from kthread_create()). |
160 | */ |
161 | void kthread_bind(struct task_struct *p, unsigned int cpu) |
162 | { |
163 | /* Must have done schedule() in kthread() before we set_task_cpu */ |
164 | if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) { |
165 | WARN_ON(1); |
166 | return; |
167 | } |
168 | |
169 | p->cpus_allowed = cpumask_of_cpu(cpu); |
170 | p->rt.nr_cpus_allowed = 1; |
171 | p->flags |= PF_THREAD_BOUND; |
172 | } |
173 | EXPORT_SYMBOL(kthread_bind); |
174 | |
175 | /** |
176 | * kthread_stop - stop a thread created by kthread_create(). |
177 | * @k: thread created by kthread_create(). |
178 | * |
179 | * Sets kthread_should_stop() for @k to return true, wakes it, and |
180 | * waits for it to exit. This can also be called after kthread_create() |
181 | * instead of calling wake_up_process(): the thread will exit without |
182 | * calling threadfn(). |
183 | * |
184 | * If threadfn() may call do_exit() itself, the caller must ensure |
185 | * task_struct can't go away. |
186 | * |
187 | * Returns the result of threadfn(), or %-EINTR if wake_up_process() |
188 | * was never called. |
189 | */ |
190 | int kthread_stop(struct task_struct *k) |
191 | { |
192 | struct kthread *kthread; |
193 | int ret; |
194 | |
195 | trace_sched_kthread_stop(k); |
196 | get_task_struct(k); |
197 | |
198 | kthread = to_kthread(k); |
199 | barrier(); /* it might have exited */ |
200 | if (k->vfork_done != NULL) { |
201 | kthread->should_stop = 1; |
202 | wake_up_process(k); |
203 | wait_for_completion(&kthread->exited); |
204 | } |
205 | ret = k->exit_code; |
206 | |
207 | put_task_struct(k); |
208 | trace_sched_kthread_stop_ret(ret); |
209 | |
210 | return ret; |
211 | } |
212 | EXPORT_SYMBOL(kthread_stop); |
213 | |
214 | int kthreadd(void *unused) |
215 | { |
216 | struct task_struct *tsk = current; |
217 | |
218 | /* Setup a clean context for our children to inherit. */ |
219 | set_task_comm(tsk, "kthreadd"); |
220 | ignore_signals(tsk); |
221 | set_cpus_allowed_ptr(tsk, cpu_all_mask); |
222 | set_mems_allowed(node_states[N_HIGH_MEMORY]); |
223 | |
224 | current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG; |
225 | |
226 | for (;;) { |
227 | set_current_state(TASK_INTERRUPTIBLE); |
228 | if (list_empty(&kthread_create_list)) |
229 | schedule(); |
230 | __set_current_state(TASK_RUNNING); |
231 | |
232 | spin_lock(&kthread_create_lock); |
233 | while (!list_empty(&kthread_create_list)) { |
234 | struct kthread_create_info *create; |
235 | |
236 | create = list_entry(kthread_create_list.next, |
237 | struct kthread_create_info, list); |
238 | list_del_init(&create->list); |
239 | spin_unlock(&kthread_create_lock); |
240 | |
241 | create_kthread(create); |
242 | |
243 | spin_lock(&kthread_create_lock); |
244 | } |
245 | spin_unlock(&kthread_create_lock); |
246 | } |
247 | |
248 | return 0; |
249 | } |
250 |
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