projects/linux·blob v2.6.31 · refs

253 lines · 6.7 KiB

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#define KTHREAD_NICE_LEVEL (-5)
20
21static DEFINE_SPINLOCK(kthread_create_lock);
22static LIST_HEAD(kthread_create_list);
23struct task_struct *kthreadd_task;
24
25struct kthread_create_info
26{
27 /* Information passed to kthread() from kthreadd. */
28 int (*threadfn)(void *data);
29 void *data;
30
31 /* Result passed back to kthread_create() from kthreadd. */
32 struct task_struct *result;
33 struct completion done;
34
35 struct list_head list;
36};
37
38struct kthread {
39 int should_stop;
40 struct completion exited;
41};
42
43#define to_kthread(tsk) \
44 container_of((tsk)->vfork_done, struct kthread, exited)
45
46/**
47 * kthread_should_stop - should this kthread return now?
48 *
49 * When someone calls kthread_stop() on your kthread, it will be woken
50 * and this will return true. You should then return, and your return
51 * value will be passed through to kthread_stop().
52 */
53int kthread_should_stop(void)
54{
55 return to_kthread(current)->should_stop;
56}
57EXPORT_SYMBOL(kthread_should_stop);
58
59static int kthread(void *_create)
60{
61 /* Copy data: it's on kthread's stack */
62 struct kthread_create_info *create = _create;
63 int (*threadfn)(void *data) = create->threadfn;
64 void *data = create->data;
65 struct kthread self;
66 int ret;
67
68 self.should_stop = 0;
69 init_completion(&self.exited);
70 current->vfork_done = &self.exited;
71
72 /* OK, tell user we're spawned, wait for stop or wakeup */
73 __set_current_state(TASK_UNINTERRUPTIBLE);
74 create->result = current;
75 complete(&create->done);
76 schedule();
77
78 ret = -EINTR;
79 if (!self.should_stop)
80 ret = threadfn(data);
81
82 /* we can't just return, we must preserve "self" on stack */
83 do_exit(ret);
84}
85
86static void create_kthread(struct kthread_create_info *create)
87{
88 int pid;
89
90 /* We want our own signal handler (we take no signals by default). */
91 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
92 if (pid < 0) {
93 create->result = ERR_PTR(pid);
94 complete(&create->done);
95 }
96}
97
98/**
99 * kthread_create - create a kthread.
100 * @threadfn: the function to run until signal_pending(current).
101 * @data: data ptr for @threadfn.
102 * @namefmt: printf-style name for the thread.
103 *
104 * Description: This helper function creates and names a kernel
105 * thread. The thread will be stopped: use wake_up_process() to start
106 * it. See also kthread_run(), kthread_create_on_cpu().
107 *
108 * When woken, the thread will run @threadfn() with @data as its
109 * argument. @threadfn() can either call do_exit() directly if it is a
110 * standalone thread for which noone will call kthread_stop(), or
111 * return when 'kthread_should_stop()' is true (which means
112 * kthread_stop() has been called). The return value should be zero
113 * or a negative error number; it will be passed to kthread_stop().
114 *
115 * Returns a task_struct or ERR_PTR(-ENOMEM).
116 */
117struct task_struct *kthread_create(int (*threadfn)(void *data),
118 void *data,
119 const char namefmt[],
120 ...)
121{
122 struct kthread_create_info create;
123
124 create.threadfn = threadfn;
125 create.data = data;
126 init_completion(&create.done);
127
128 spin_lock(&kthread_create_lock);
129 list_add_tail(&create.list, &kthread_create_list);
130 spin_unlock(&kthread_create_lock);
131
132 wake_up_process(kthreadd_task);
133 wait_for_completion(&create.done);
134
135 if (!IS_ERR(create.result)) {
136 struct sched_param param = { .sched_priority = 0 };
137 va_list args;
138
139 va_start(args, namefmt);
140 vsnprintf(create.result->comm, sizeof(create.result->comm),
141 namefmt, args);
142 va_end(args);
143 /*
144 * root may have changed our (kthreadd's) priority or CPU mask.
145 * The kernel thread should not inherit these properties.
146 */
147 sched_setscheduler_nocheck(create.result, SCHED_NORMAL, &param);
148 set_user_nice(create.result, KTHREAD_NICE_LEVEL);
149 set_cpus_allowed_ptr(create.result, cpu_all_mask);
150 }
151 return create.result;
152}
153EXPORT_SYMBOL(kthread_create);
154
155/**
156 * kthread_bind - bind a just-created kthread to a cpu.
157 * @k: thread created by kthread_create().
158 * @cpu: cpu (might not be online, must be possible) for @k to run on.
159 *
160 * Description: This function is equivalent to set_cpus_allowed(),
161 * except that @cpu doesn't need to be online, and the thread must be
162 * stopped (i.e., just returned from kthread_create()).
163 */
164void kthread_bind(struct task_struct *k, unsigned int cpu)
165{
166 /* Must have done schedule() in kthread() before we set_task_cpu */
167 if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) {
168 WARN_ON(1);
169 return;
170 }
171 set_task_cpu(k, cpu);
172 k->cpus_allowed = cpumask_of_cpu(cpu);
173 k->rt.nr_cpus_allowed = 1;
174 k->flags |= PF_THREAD_BOUND;
175}
176EXPORT_SYMBOL(kthread_bind);
177
178/**
179 * kthread_stop - stop a thread created by kthread_create().
180 * @k: thread created by kthread_create().
181 *
182 * Sets kthread_should_stop() for @k to return true, wakes it, and
183 * waits for it to exit. This can also be called after kthread_create()
184 * instead of calling wake_up_process(): the thread will exit without
185 * calling threadfn().
186 *
187 * If threadfn() may call do_exit() itself, the caller must ensure
188 * task_struct can't go away.
189 *
190 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
191 * was never called.
192 */
193int kthread_stop(struct task_struct *k)
194{
195 struct kthread *kthread;
196 int ret;
197
198 trace_sched_kthread_stop(k);
199 get_task_struct(k);
200
201 kthread = to_kthread(k);
202 barrier(); /* it might have exited */
203 if (k->vfork_done != NULL) {
204 kthread->should_stop = 1;
205 wake_up_process(k);
206 wait_for_completion(&kthread->exited);
207 }
208 ret = k->exit_code;
209
210 put_task_struct(k);
211 trace_sched_kthread_stop_ret(ret);
212
213 return ret;
214}
215EXPORT_SYMBOL(kthread_stop);
216
217int kthreadd(void *unused)
218{
219 struct task_struct *tsk = current;
220
221 /* Setup a clean context for our children to inherit. */
222 set_task_comm(tsk, "kthreadd");
223 ignore_signals(tsk);
224 set_user_nice(tsk, KTHREAD_NICE_LEVEL);
225 set_cpus_allowed_ptr(tsk, cpu_all_mask);
226 set_mems_allowed(node_possible_map);
227
228 current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
229
230 for (;;) {
231 set_current_state(TASK_INTERRUPTIBLE);
232 if (list_empty(&kthread_create_list))
233 schedule();
234 __set_current_state(TASK_RUNNING);
235
236 spin_lock(&kthread_create_lock);
237 while (!list_empty(&kthread_create_list)) {
238 struct kthread_create_info *create;
239
240 create = list_entry(kthread_create_list.next,
241 struct kthread_create_info, list);
242 list_del_init(&create->list);
243 spin_unlock(&kthread_create_lock);
244
245 create_kthread(create);
246
247 spin_lock(&kthread_create_lock);
248 }
249 spin_unlock(&kthread_create_lock);
250 }
251
252 return 0;
253}