projects/linux·blob v2.6.32-rc7 · refs

226 lines · 5.9 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
19static DEFINE_SPINLOCK(kthread_create_lock);
20static LIST_HEAD(kthread_create_list);
21struct task_struct *kthreadd_task;
22
23struct 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
36struct 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 */
51int kthread_should_stop(void)
52{
53 return to_kthread(current)->should_stop;
54}
55EXPORT_SYMBOL(kthread_should_stop);
56
57static 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
84static 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(), kthread_create_on_cpu().
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 */
115struct 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, &param);
146 set_cpus_allowed_ptr(create.result, cpu_all_mask);
147 }
148 return create.result;
149}
150EXPORT_SYMBOL(kthread_create);
151
152/**
153 * kthread_stop - stop a thread created by kthread_create().
154 * @k: thread created by kthread_create().
155 *
156 * Sets kthread_should_stop() for @k to return true, wakes it, and
157 * waits for it to exit. This can also be called after kthread_create()
158 * instead of calling wake_up_process(): the thread will exit without
159 * calling threadfn().
160 *
161 * If threadfn() may call do_exit() itself, the caller must ensure
162 * task_struct can't go away.
163 *
164 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
165 * was never called.
166 */
167int kthread_stop(struct task_struct *k)
168{
169 struct kthread *kthread;
170 int ret;
171
172 trace_sched_kthread_stop(k);
173 get_task_struct(k);
174
175 kthread = to_kthread(k);
176 barrier(); /* it might have exited */
177 if (k->vfork_done != NULL) {
178 kthread->should_stop = 1;
179 wake_up_process(k);
180 wait_for_completion(&kthread->exited);
181 }
182 ret = k->exit_code;
183
184 put_task_struct(k);
185 trace_sched_kthread_stop_ret(ret);
186
187 return ret;
188}
189EXPORT_SYMBOL(kthread_stop);
190
191int kthreadd(void *unused)
192{
193 struct task_struct *tsk = current;
194
195 /* Setup a clean context for our children to inherit. */
196 set_task_comm(tsk, "kthreadd");
197 ignore_signals(tsk);
198 set_cpus_allowed_ptr(tsk, cpu_all_mask);
199 set_mems_allowed(node_possible_map);
200
201 current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
202
203 for (;;) {
204 set_current_state(TASK_INTERRUPTIBLE);
205 if (list_empty(&kthread_create_list))
206 schedule();
207 __set_current_state(TASK_RUNNING);
208
209 spin_lock(&kthread_create_lock);
210 while (!list_empty(&kthread_create_list)) {
211 struct kthread_create_info *create;
212
213 create = list_entry(kthread_create_list.next,
214 struct kthread_create_info, list);
215 list_del_init(&create->list);
216 spin_unlock(&kthread_create_lock);
217
218 create_kthread(create);
219
220 spin_lock(&kthread_create_lock);
221 }
222 spin_unlock(&kthread_create_lock);
223 }
224
225 return 0;
226}