projects/linux·blob v2.6.29 · refs

270 lines · 7.4 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/unistd.h>
13#include <linux/file.h>
14#include <linux/module.h>
15#include <linux/mutex.h>
16#include <trace/sched.h>
17
18#define KTHREAD_NICE_LEVEL (-5)
19
20static DEFINE_SPINLOCK(kthread_create_lock);
21static LIST_HEAD(kthread_create_list);
22struct task_struct *kthreadd_task;
23
24DEFINE_TRACE(sched_kthread_stop);
25DEFINE_TRACE(sched_kthread_stop_ret);
26
27struct kthread_create_info
28{
29 /* Information passed to kthread() from kthreadd. */
30 int (*threadfn)(void *data);
31 void *data;
32 struct completion started;
33
34 /* Result passed back to kthread_create() from kthreadd. */
35 struct task_struct *result;
36 struct completion done;
37
38 struct list_head list;
39};
40
41struct 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. */
50static DEFINE_MUTEX(kthread_stop_lock);
51static struct kthread_stop_info kthread_stop_info;
52
53/**
54 * kthread_should_stop - should this kthread return now?
55 *
56 * When someone calls kthread_stop() on your kthread, it will be woken
57 * and this will return true. You should then return, and your return
58 * value will be passed through to kthread_stop().
59 */
60int kthread_should_stop(void)
61{
62 return (kthread_stop_info.k == current);
63}
64EXPORT_SYMBOL(kthread_should_stop);
65
66static int kthread(void *_create)
67{
68 struct kthread_create_info *create = _create;
69 int (*threadfn)(void *data);
70 void *data;
71 int ret = -EINTR;
72
73 /* Copy data: it's on kthread's stack */
74 threadfn = create->threadfn;
75 data = create->data;
76
77 /* OK, tell user we're spawned, wait for stop or wakeup */
78 __set_current_state(TASK_UNINTERRUPTIBLE);
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
93static void create_kthread(struct kthread_create_info *create)
94{
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 {
102 struct sched_param param = { .sched_priority = 0 };
103 wait_for_completion(&create->started);
104 read_lock(&tasklist_lock);
105 create->result = find_task_by_pid_ns(pid, &init_pid_ns);
106 read_unlock(&tasklist_lock);
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, &param);
112 set_user_nice(create->result, KTHREAD_NICE_LEVEL);
113 set_cpus_allowed_ptr(create->result, CPU_MASK_ALL_PTR);
114 }
115 complete(&create->done);
116}
117
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
129 * argument. @threadfn() can either call do_exit() directly if it is a
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 */
137struct task_struct *kthread_create(int (*threadfn)(void *data),
138 void *data,
139 const char namefmt[],
140 ...)
141{
142 struct kthread_create_info create;
143
144 create.threadfn = threadfn;
145 create.data = data;
146 init_completion(&create.started);
147 init_completion(&create.done);
148
149 spin_lock(&kthread_create_lock);
150 list_add_tail(&create.list, &kthread_create_list);
151 spin_unlock(&kthread_create_lock);
152
153 wake_up_process(kthreadd_task);
154 wait_for_completion(&create.done);
155
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 }
163 return create.result;
164}
165EXPORT_SYMBOL(kthread_create);
166
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
174 * stopped (i.e., just returned from kthread_create()).
175 */
176void kthread_bind(struct task_struct *k, unsigned int cpu)
177{
178 /* Must have done schedule() in kthread() before we set_task_cpu */
179 if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) {
180 WARN_ON(1);
181 return;
182 }
183 set_task_cpu(k, cpu);
184 k->cpus_allowed = cpumask_of_cpu(cpu);
185 k->rt.nr_cpus_allowed = 1;
186 k->flags |= PF_THREAD_BOUND;
187}
188EXPORT_SYMBOL(kthread_bind);
189
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 */
203int kthread_stop(struct task_struct *k)
204{
205 int ret;
206
207 mutex_lock(&kthread_stop_lock);
208
209 /* It could exit after stop_info.k set, but before wake_up_process. */
210 get_task_struct(k);
211
212 trace_sched_kthread_stop(k);
213
214 /* Must init completion *before* thread sees kthread_stop_info.k */
215 init_completion(&kthread_stop_info.done);
216 smp_wmb();
217
218 /* Now set kthread_should_stop() to true, and wake it up. */
219 kthread_stop_info.k = k;
220 wake_up_process(k);
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;
227 mutex_unlock(&kthread_stop_lock);
228
229 trace_sched_kthread_stop_ret(ret);
230
231 return ret;
232}
233EXPORT_SYMBOL(kthread_stop);
234
235int kthreadd(void *unused)
236{
237 struct task_struct *tsk = current;
238
239 /* Setup a clean context for our children to inherit. */
240 set_task_comm(tsk, "kthreadd");
241 ignore_signals(tsk);
242 set_user_nice(tsk, KTHREAD_NICE_LEVEL);
243 set_cpus_allowed_ptr(tsk, CPU_MASK_ALL_PTR);
244
245 current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
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}