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> |
0a16b607 | 16 | #include <trace/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 | 23 | |
7e066fb8 MD |
24 | DEFINE_TRACE(sched_kthread_stop); |
25 | DEFINE_TRACE(sched_kthread_stop_ret); | |
26 | ||
1da177e4 LT |
27 | struct kthread_create_info |
28 | { | |
73c27992 | 29 | /* Information passed to kthread() from kthreadd. */ |
1da177e4 LT |
30 | int (*threadfn)(void *data); |
31 | void *data; | |
32 | struct completion started; | |
33 | ||
73c27992 | 34 | /* Result passed back to kthread_create() from kthreadd. */ |
1da177e4 LT |
35 | struct task_struct *result; |
36 | struct completion done; | |
65f27f38 | 37 | |
73c27992 | 38 | struct list_head list; |
1da177e4 LT |
39 | }; |
40 | ||
41 | struct kthread_stop_info | |
42 | { | |
43 | struct task_struct *k; | |
44 | int err; | |
45 | struct completion done; | |
46 | }; | |
47 | ||
48 | /* Thread stopping is done by setthing this var: lock serializes | |
49 | * multiple kthread_stop calls. */ | |
97d1f15b | 50 | static DEFINE_MUTEX(kthread_stop_lock); |
1da177e4 LT |
51 | static struct kthread_stop_info kthread_stop_info; |
52 | ||
9e37bd30 RD |
53 | /** |
54 | * kthread_should_stop - should this kthread return now? | |
55 | * | |
72fd4a35 | 56 | * When someone calls kthread_stop() on your kthread, it will be woken |
9e37bd30 RD |
57 | * and this will return true. You should then return, and your return |
58 | * value will be passed through to kthread_stop(). | |
59 | */ | |
1da177e4 LT |
60 | int kthread_should_stop(void) |
61 | { | |
62 | return (kthread_stop_info.k == current); | |
63 | } | |
64 | EXPORT_SYMBOL(kthread_should_stop); | |
65 | ||
1da177e4 LT |
66 | static int kthread(void *_create) |
67 | { | |
68 | struct kthread_create_info *create = _create; | |
69 | int (*threadfn)(void *data); | |
70 | void *data; | |
1da177e4 LT |
71 | int ret = -EINTR; |
72 | ||
73c27992 | 73 | /* Copy data: it's on kthread's stack */ |
1da177e4 LT |
74 | threadfn = create->threadfn; |
75 | data = create->data; | |
76 | ||
1da177e4 | 77 | /* OK, tell user we're spawned, wait for stop or wakeup */ |
a076e4bc | 78 | __set_current_state(TASK_UNINTERRUPTIBLE); |
1da177e4 LT |
79 | complete(&create->started); |
80 | schedule(); | |
81 | ||
82 | if (!kthread_should_stop()) | |
83 | ret = threadfn(data); | |
84 | ||
85 | /* It might have exited on its own, w/o kthread_stop. Check. */ | |
86 | if (kthread_should_stop()) { | |
87 | kthread_stop_info.err = ret; | |
88 | complete(&kthread_stop_info.done); | |
89 | } | |
90 | return 0; | |
91 | } | |
92 | ||
73c27992 | 93 | static void create_kthread(struct kthread_create_info *create) |
1da177e4 | 94 | { |
1da177e4 LT |
95 | int pid; |
96 | ||
97 | /* We want our own signal handler (we take no signals by default). */ | |
98 | pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD); | |
99 | if (pid < 0) { | |
100 | create->result = ERR_PTR(pid); | |
101 | } else { | |
4f05b98d | 102 | struct sched_param param = { .sched_priority = 0 }; |
1da177e4 | 103 | wait_for_completion(&create->started); |
05eeae20 | 104 | read_lock(&tasklist_lock); |
5cd20455 | 105 | create->result = find_task_by_pid_ns(pid, &init_pid_ns); |
05eeae20 | 106 | read_unlock(&tasklist_lock); |
4f05b98d MS |
107 | /* |
108 | * root may have changed our (kthreadd's) priority or CPU mask. | |
109 | * The kernel thread should not inherit these properties. | |
110 | */ | |
111 | sched_setscheduler(create->result, SCHED_NORMAL, ¶m); | |
112 | set_user_nice(create->result, KTHREAD_NICE_LEVEL); | |
8df185a9 | 113 | set_cpus_allowed_ptr(create->result, CPU_MASK_ALL_PTR); |
1da177e4 LT |
114 | } |
115 | complete(&create->done); | |
116 | } | |
117 | ||
9e37bd30 RD |
118 | /** |
119 | * kthread_create - create a kthread. | |
120 | * @threadfn: the function to run until signal_pending(current). | |
121 | * @data: data ptr for @threadfn. | |
122 | * @namefmt: printf-style name for the thread. | |
123 | * | |
124 | * Description: This helper function creates and names a kernel | |
125 | * thread. The thread will be stopped: use wake_up_process() to start | |
126 | * it. See also kthread_run(), kthread_create_on_cpu(). | |
127 | * | |
128 | * When woken, the thread will run @threadfn() with @data as its | |
72fd4a35 | 129 | * argument. @threadfn() can either call do_exit() directly if it is a |
9e37bd30 RD |
130 | * standalone thread for which noone will call kthread_stop(), or |
131 | * return when 'kthread_should_stop()' is true (which means | |
132 | * kthread_stop() has been called). The return value should be zero | |
133 | * or a negative error number; it will be passed to kthread_stop(). | |
134 | * | |
135 | * Returns a task_struct or ERR_PTR(-ENOMEM). | |
136 | */ | |
1da177e4 LT |
137 | struct task_struct *kthread_create(int (*threadfn)(void *data), |
138 | void *data, | |
139 | const char namefmt[], | |
140 | ...) | |
141 | { | |
142 | struct kthread_create_info create; | |
1da177e4 LT |
143 | |
144 | create.threadfn = threadfn; | |
145 | create.data = data; | |
146 | init_completion(&create.started); | |
147 | init_completion(&create.done); | |
73c27992 EB |
148 | |
149 | spin_lock(&kthread_create_lock); | |
150 | list_add_tail(&create.list, &kthread_create_list); | |
73c27992 EB |
151 | spin_unlock(&kthread_create_lock); |
152 | ||
cbd9b67b | 153 | wake_up_process(kthreadd_task); |
73c27992 EB |
154 | wait_for_completion(&create.done); |
155 | ||
1da177e4 LT |
156 | if (!IS_ERR(create.result)) { |
157 | va_list args; | |
158 | va_start(args, namefmt); | |
159 | vsnprintf(create.result->comm, sizeof(create.result->comm), | |
160 | namefmt, args); | |
161 | va_end(args); | |
162 | } | |
1da177e4 LT |
163 | return create.result; |
164 | } | |
165 | EXPORT_SYMBOL(kthread_create); | |
166 | ||
9e37bd30 RD |
167 | /** |
168 | * kthread_bind - bind a just-created kthread to a cpu. | |
169 | * @k: thread created by kthread_create(). | |
170 | * @cpu: cpu (might not be online, must be possible) for @k to run on. | |
171 | * | |
172 | * Description: This function is equivalent to set_cpus_allowed(), | |
173 | * except that @cpu doesn't need to be online, and the thread must be | |
72fd4a35 | 174 | * stopped (i.e., just returned from kthread_create()). |
9e37bd30 | 175 | */ |
1da177e4 LT |
176 | void kthread_bind(struct task_struct *k, unsigned int cpu) |
177 | { | |
293adee6 ON |
178 | /* Must have done schedule() in kthread() before we set_task_cpu */ |
179 | if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) { | |
a076e4bc ON |
180 | WARN_ON(1); |
181 | return; | |
182 | } | |
1da177e4 LT |
183 | set_task_cpu(k, cpu); |
184 | k->cpus_allowed = cpumask_of_cpu(cpu); | |
9f0e738f | 185 | k->rt.nr_cpus_allowed = 1; |
9985b0ba | 186 | k->flags |= PF_THREAD_BOUND; |
1da177e4 LT |
187 | } |
188 | EXPORT_SYMBOL(kthread_bind); | |
189 | ||
9e37bd30 RD |
190 | /** |
191 | * kthread_stop - stop a thread created by kthread_create(). | |
192 | * @k: thread created by kthread_create(). | |
193 | * | |
194 | * Sets kthread_should_stop() for @k to return true, wakes it, and | |
195 | * waits for it to exit. Your threadfn() must not call do_exit() | |
196 | * itself if you use this function! This can also be called after | |
197 | * kthread_create() instead of calling wake_up_process(): the thread | |
198 | * will exit without calling threadfn(). | |
199 | * | |
200 | * Returns the result of threadfn(), or %-EINTR if wake_up_process() | |
201 | * was never called. | |
202 | */ | |
1da177e4 LT |
203 | int kthread_stop(struct task_struct *k) |
204 | { | |
205 | int ret; | |
206 | ||
97d1f15b | 207 | mutex_lock(&kthread_stop_lock); |
1da177e4 LT |
208 | |
209 | /* It could exit after stop_info.k set, but before wake_up_process. */ | |
210 | get_task_struct(k); | |
211 | ||
0a16b607 MD |
212 | trace_sched_kthread_stop(k); |
213 | ||
1da177e4 LT |
214 | /* Must init completion *before* thread sees kthread_stop_info.k */ |
215 | init_completion(&kthread_stop_info.done); | |
d59dd462 | 216 | smp_wmb(); |
1da177e4 LT |
217 | |
218 | /* Now set kthread_should_stop() to true, and wake it up. */ | |
219 | kthread_stop_info.k = k; | |
52e92e57 | 220 | wake_up_process(k); |
1da177e4 LT |
221 | put_task_struct(k); |
222 | ||
223 | /* Once it dies, reset stop ptr, gather result and we're done. */ | |
224 | wait_for_completion(&kthread_stop_info.done); | |
225 | kthread_stop_info.k = NULL; | |
226 | ret = kthread_stop_info.err; | |
97d1f15b | 227 | mutex_unlock(&kthread_stop_lock); |
1da177e4 | 228 | |
0a16b607 MD |
229 | trace_sched_kthread_stop_ret(ret); |
230 | ||
1da177e4 LT |
231 | return ret; |
232 | } | |
52e92e57 | 233 | EXPORT_SYMBOL(kthread_stop); |
1da177e4 | 234 | |
e804a4a4 | 235 | int kthreadd(void *unused) |
1da177e4 | 236 | { |
73c27992 | 237 | struct task_struct *tsk = current; |
1da177e4 | 238 | |
e804a4a4 | 239 | /* Setup a clean context for our children to inherit. */ |
73c27992 | 240 | set_task_comm(tsk, "kthreadd"); |
10ab825b | 241 | ignore_signals(tsk); |
4f05b98d | 242 | set_user_nice(tsk, KTHREAD_NICE_LEVEL); |
8df185a9 | 243 | set_cpus_allowed_ptr(tsk, CPU_MASK_ALL_PTR); |
73c27992 | 244 | |
ebb12db5 | 245 | current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG; |
73c27992 EB |
246 | |
247 | for (;;) { | |
248 | set_current_state(TASK_INTERRUPTIBLE); | |
249 | if (list_empty(&kthread_create_list)) | |
250 | schedule(); | |
251 | __set_current_state(TASK_RUNNING); | |
252 | ||
253 | spin_lock(&kthread_create_lock); | |
254 | while (!list_empty(&kthread_create_list)) { | |
255 | struct kthread_create_info *create; | |
256 | ||
257 | create = list_entry(kthread_create_list.next, | |
258 | struct kthread_create_info, list); | |
259 | list_del_init(&create->list); | |
260 | spin_unlock(&kthread_create_lock); | |
261 | ||
262 | create_kthread(create); | |
263 | ||
264 | spin_lock(&kthread_create_lock); | |
265 | } | |
266 | spin_unlock(&kthread_create_lock); | |
267 | } | |
268 | ||
269 | return 0; | |
270 | } |