1 /* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
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,
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>
19 #define KTHREAD_NICE_LEVEL (-5)
21 static DEFINE_SPINLOCK(kthread_create_lock);
22 static LIST_HEAD(kthread_create_list);
23 struct task_struct *kthreadd_task;
25 struct kthread_create_info
27 /* Information passed to kthread() from kthreadd. */
28 int (*threadfn)(void *data);
31 /* Result passed back to kthread_create() from kthreadd. */
32 struct task_struct *result;
33 struct completion done;
35 struct list_head list;
38 struct kthread_stop_info
40 struct task_struct *k;
42 struct completion done;
45 /* Thread stopping is done by setthing this var: lock serializes
46 * multiple kthread_stop calls. */
47 static DEFINE_MUTEX(kthread_stop_lock);
48 static struct kthread_stop_info kthread_stop_info;
51 * kthread_should_stop - should this kthread return now?
53 * When someone calls kthread_stop() on your kthread, it will be woken
54 * and this will return true. You should then return, and your return
55 * value will be passed through to kthread_stop().
57 int kthread_should_stop(void)
59 return (kthread_stop_info.k == current);
61 EXPORT_SYMBOL(kthread_should_stop);
63 static int kthread(void *_create)
65 struct kthread_create_info *create = _create;
66 int (*threadfn)(void *data);
70 /* Copy data: it's on kthread's stack */
71 threadfn = create->threadfn;
74 /* OK, tell user we're spawned, wait for stop or wakeup */
75 __set_current_state(TASK_UNINTERRUPTIBLE);
76 create->result = current;
77 complete(&create->done);
80 if (!kthread_should_stop())
83 /* It might have exited on its own, w/o kthread_stop. Check. */
84 if (kthread_should_stop()) {
85 kthread_stop_info.err = ret;
86 complete(&kthread_stop_info.done);
91 static void create_kthread(struct kthread_create_info *create)
95 /* We want our own signal handler (we take no signals by default). */
96 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
98 create->result = ERR_PTR(pid);
99 complete(&create->done);
104 * kthread_create - create a kthread.
105 * @threadfn: the function to run until signal_pending(current).
106 * @data: data ptr for @threadfn.
107 * @namefmt: printf-style name for the thread.
109 * Description: This helper function creates and names a kernel
110 * thread. The thread will be stopped: use wake_up_process() to start
111 * it. See also kthread_run(), kthread_create_on_cpu().
113 * When woken, the thread will run @threadfn() with @data as its
114 * argument. @threadfn() can either call do_exit() directly if it is a
115 * standalone thread for which noone will call kthread_stop(), or
116 * return when 'kthread_should_stop()' is true (which means
117 * kthread_stop() has been called). The return value should be zero
118 * or a negative error number; it will be passed to kthread_stop().
120 * Returns a task_struct or ERR_PTR(-ENOMEM).
122 struct task_struct *kthread_create(int (*threadfn)(void *data),
124 const char namefmt[],
127 struct kthread_create_info create;
129 create.threadfn = threadfn;
131 init_completion(&create.done);
133 spin_lock(&kthread_create_lock);
134 list_add_tail(&create.list, &kthread_create_list);
135 spin_unlock(&kthread_create_lock);
137 wake_up_process(kthreadd_task);
138 wait_for_completion(&create.done);
140 if (!IS_ERR(create.result)) {
141 struct sched_param param = { .sched_priority = 0 };
144 va_start(args, namefmt);
145 vsnprintf(create.result->comm, sizeof(create.result->comm),
149 * root may have changed our (kthreadd's) priority or CPU mask.
150 * The kernel thread should not inherit these properties.
152 sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m);
153 set_user_nice(create.result, KTHREAD_NICE_LEVEL);
154 set_cpus_allowed_ptr(create.result, cpu_all_mask);
156 return create.result;
158 EXPORT_SYMBOL(kthread_create);
161 * kthread_bind - bind a just-created kthread to a cpu.
162 * @k: thread created by kthread_create().
163 * @cpu: cpu (might not be online, must be possible) for @k to run on.
165 * Description: This function is equivalent to set_cpus_allowed(),
166 * except that @cpu doesn't need to be online, and the thread must be
167 * stopped (i.e., just returned from kthread_create()).
169 void kthread_bind(struct task_struct *k, unsigned int cpu)
171 /* Must have done schedule() in kthread() before we set_task_cpu */
172 if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) {
176 set_task_cpu(k, cpu);
177 k->cpus_allowed = cpumask_of_cpu(cpu);
178 k->rt.nr_cpus_allowed = 1;
179 k->flags |= PF_THREAD_BOUND;
181 EXPORT_SYMBOL(kthread_bind);
184 * kthread_stop - stop a thread created by kthread_create().
185 * @k: thread created by kthread_create().
187 * Sets kthread_should_stop() for @k to return true, wakes it, and
188 * waits for it to exit. Your threadfn() must not call do_exit()
189 * itself if you use this function! This can also be called after
190 * kthread_create() instead of calling wake_up_process(): the thread
191 * will exit without calling threadfn().
193 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
196 int kthread_stop(struct task_struct *k)
200 mutex_lock(&kthread_stop_lock);
202 /* It could exit after stop_info.k set, but before wake_up_process. */
205 trace_sched_kthread_stop(k);
207 /* Must init completion *before* thread sees kthread_stop_info.k */
208 init_completion(&kthread_stop_info.done);
211 /* Now set kthread_should_stop() to true, and wake it up. */
212 kthread_stop_info.k = k;
216 /* Once it dies, reset stop ptr, gather result and we're done. */
217 wait_for_completion(&kthread_stop_info.done);
218 kthread_stop_info.k = NULL;
219 ret = kthread_stop_info.err;
220 mutex_unlock(&kthread_stop_lock);
222 trace_sched_kthread_stop_ret(ret);
226 EXPORT_SYMBOL(kthread_stop);
228 int kthreadd(void *unused)
230 struct task_struct *tsk = current;
232 /* Setup a clean context for our children to inherit. */
233 set_task_comm(tsk, "kthreadd");
235 set_user_nice(tsk, KTHREAD_NICE_LEVEL);
236 set_cpus_allowed_ptr(tsk, cpu_all_mask);
237 set_mems_allowed(node_possible_map);
239 current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
242 set_current_state(TASK_INTERRUPTIBLE);
243 if (list_empty(&kthread_create_list))
245 __set_current_state(TASK_RUNNING);
247 spin_lock(&kthread_create_lock);
248 while (!list_empty(&kthread_create_list)) {
249 struct kthread_create_info *create;
251 create = list_entry(kthread_create_list.next,
252 struct kthread_create_info, list);
253 list_del_init(&create->list);
254 spin_unlock(&kthread_create_lock);
256 create_kthread(create);
258 spin_lock(&kthread_create_lock);
260 spin_unlock(&kthread_create_lock);