blob: 41c88fe40500399c76f0382d51a3fb05aef03211 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
3 *
Eric W. Biederman73c27992007-05-09 02:34:32 -07004 * Creation is done via kthreadd, so that we get a clean environment
Linus Torvalds1da177e2005-04-16 15:20:36 -07005 * 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>
Arjan van de Ven97d1f152006-03-23 03:00:24 -080015#include <linux/mutex.h>
Steven Rostedtad8d75f2009-04-14 19:39:12 -040016#include <trace/events/sched.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070017
Michal Schmidt4f05b982008-01-25 21:08:33 +010018#define KTHREAD_NICE_LEVEL (-5)
19
Eric W. Biederman73c27992007-05-09 02:34:32 -070020static DEFINE_SPINLOCK(kthread_create_lock);
21static LIST_HEAD(kthread_create_list);
22struct task_struct *kthreadd_task;
Linus Torvalds1da177e2005-04-16 15:20:36 -070023
24struct kthread_create_info
25{
Eric W. Biederman73c27992007-05-09 02:34:32 -070026 /* Information passed to kthread() from kthreadd. */
Linus Torvalds1da177e2005-04-16 15:20:36 -070027 int (*threadfn)(void *data);
28 void *data;
29 struct completion started;
30
Eric W. Biederman73c27992007-05-09 02:34:32 -070031 /* Result passed back to kthread_create() from kthreadd. */
Linus Torvalds1da177e2005-04-16 15:20:36 -070032 struct task_struct *result;
33 struct completion done;
David Howells65f27f32006-11-22 14:55:48 +000034
Eric W. Biederman73c27992007-05-09 02:34:32 -070035 struct list_head list;
Linus Torvalds1da177e2005-04-16 15:20:36 -070036};
37
38struct kthread_stop_info
39{
40 struct task_struct *k;
41 int err;
42 struct completion done;
43};
44
45/* Thread stopping is done by setthing this var: lock serializes
46 * multiple kthread_stop calls. */
Arjan van de Ven97d1f152006-03-23 03:00:24 -080047static DEFINE_MUTEX(kthread_stop_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070048static struct kthread_stop_info kthread_stop_info;
49
Randy Dunlap9e37bd32006-06-25 05:49:19 -070050/**
51 * kthread_should_stop - should this kthread return now?
52 *
Robert P. J. Day72fd4a32007-02-10 01:45:59 -080053 * When someone calls kthread_stop() on your kthread, it will be woken
Randy Dunlap9e37bd32006-06-25 05:49:19 -070054 * and this will return true. You should then return, and your return
55 * value will be passed through to kthread_stop().
56 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070057int kthread_should_stop(void)
58{
59 return (kthread_stop_info.k == current);
60}
61EXPORT_SYMBOL(kthread_should_stop);
62
Linus Torvalds1da177e2005-04-16 15:20:36 -070063static int kthread(void *_create)
64{
65 struct kthread_create_info *create = _create;
66 int (*threadfn)(void *data);
67 void *data;
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 int ret = -EINTR;
69
Eric W. Biederman73c27992007-05-09 02:34:32 -070070 /* Copy data: it's on kthread's stack */
Linus Torvalds1da177e2005-04-16 15:20:36 -070071 threadfn = create->threadfn;
72 data = create->data;
73
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 /* OK, tell user we're spawned, wait for stop or wakeup */
Oleg Nesterova076e4b2007-05-23 13:57:27 -070075 __set_current_state(TASK_UNINTERRUPTIBLE);
Vitaliy Gusev3217ab92009-04-09 09:50:35 -060076 create->result = current;
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 complete(&create->started);
78 schedule();
79
80 if (!kthread_should_stop())
81 ret = threadfn(data);
82
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);
87 }
88 return 0;
89}
90
Eric W. Biederman73c27992007-05-09 02:34:32 -070091static void create_kthread(struct kthread_create_info *create)
Linus Torvalds1da177e2005-04-16 15:20:36 -070092{
Linus Torvalds1da177e2005-04-16 15:20:36 -070093 int pid;
94
95 /* We want our own signal handler (we take no signals by default). */
96 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
Oleg Nesterov1c993152009-04-09 09:50:36 -060097 if (pid < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -070098 create->result = ERR_PTR(pid);
Oleg Nesterov1c993152009-04-09 09:50:36 -060099 else
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 wait_for_completion(&create->started);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101 complete(&create->done);
102}
103
Randy Dunlap9e37bd32006-06-25 05:49:19 -0700104/**
105 * kthread_create - create a kthread.
106 * @threadfn: the function to run until signal_pending(current).
107 * @data: data ptr for @threadfn.
108 * @namefmt: printf-style name for the thread.
109 *
110 * Description: This helper function creates and names a kernel
111 * thread. The thread will be stopped: use wake_up_process() to start
112 * it. See also kthread_run(), kthread_create_on_cpu().
113 *
114 * When woken, the thread will run @threadfn() with @data as its
Robert P. J. Day72fd4a32007-02-10 01:45:59 -0800115 * argument. @threadfn() can either call do_exit() directly if it is a
Randy Dunlap9e37bd32006-06-25 05:49:19 -0700116 * standalone thread for which noone will call kthread_stop(), or
117 * return when 'kthread_should_stop()' is true (which means
118 * kthread_stop() has been called). The return value should be zero
119 * or a negative error number; it will be passed to kthread_stop().
120 *
121 * Returns a task_struct or ERR_PTR(-ENOMEM).
122 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123struct task_struct *kthread_create(int (*threadfn)(void *data),
124 void *data,
125 const char namefmt[],
126 ...)
127{
128 struct kthread_create_info create;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129
130 create.threadfn = threadfn;
131 create.data = data;
132 init_completion(&create.started);
133 init_completion(&create.done);
134
Eric W. Biederman73c27992007-05-09 02:34:32 -0700135 spin_lock(&kthread_create_lock);
136 list_add_tail(&create.list, &kthread_create_list);
Eric W. Biederman73c27992007-05-09 02:34:32 -0700137 spin_unlock(&kthread_create_lock);
138
Dmitry Adamushkocbd9b672008-04-29 00:59:23 -0700139 wake_up_process(kthreadd_task);
Eric W. Biederman73c27992007-05-09 02:34:32 -0700140 wait_for_completion(&create.done);
141
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142 if (!IS_ERR(create.result)) {
Oleg Nesterov1c993152009-04-09 09:50:36 -0600143 struct sched_param param = { .sched_priority = 0 };
Linus Torvalds1da177e2005-04-16 15:20:36 -0700144 va_list args;
Oleg Nesterov1c993152009-04-09 09:50:36 -0600145
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146 va_start(args, namefmt);
147 vsnprintf(create.result->comm, sizeof(create.result->comm),
148 namefmt, args);
149 va_end(args);
Oleg Nesterov1c993152009-04-09 09:50:36 -0600150 /*
151 * root may have changed our (kthreadd's) priority or CPU mask.
152 * The kernel thread should not inherit these properties.
153 */
154 sched_setscheduler_nocheck(create.result, SCHED_NORMAL, &param);
155 set_user_nice(create.result, KTHREAD_NICE_LEVEL);
156 set_cpus_allowed_ptr(create.result, cpu_all_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158 return create.result;
159}
160EXPORT_SYMBOL(kthread_create);
161
Randy Dunlap9e37bd32006-06-25 05:49:19 -0700162/**
163 * kthread_bind - bind a just-created kthread to a cpu.
164 * @k: thread created by kthread_create().
165 * @cpu: cpu (might not be online, must be possible) for @k to run on.
166 *
167 * Description: This function is equivalent to set_cpus_allowed(),
168 * except that @cpu doesn't need to be online, and the thread must be
Robert P. J. Day72fd4a32007-02-10 01:45:59 -0800169 * stopped (i.e., just returned from kthread_create()).
Randy Dunlap9e37bd32006-06-25 05:49:19 -0700170 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171void kthread_bind(struct task_struct *k, unsigned int cpu)
172{
Oleg Nesterov293adee2008-10-18 20:28:24 -0700173 /* Must have done schedule() in kthread() before we set_task_cpu */
174 if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) {
Oleg Nesterova076e4b2007-05-23 13:57:27 -0700175 WARN_ON(1);
176 return;
177 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178 set_task_cpu(k, cpu);
179 k->cpus_allowed = cpumask_of_cpu(cpu);
Gregory Haskins9f0e7382008-02-12 13:30:05 -0500180 k->rt.nr_cpus_allowed = 1;
David Rientjes9985b0b2008-06-05 12:57:11 -0700181 k->flags |= PF_THREAD_BOUND;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182}
183EXPORT_SYMBOL(kthread_bind);
184
Randy Dunlap9e37bd32006-06-25 05:49:19 -0700185/**
186 * kthread_stop - stop a thread created by kthread_create().
187 * @k: thread created by kthread_create().
188 *
189 * Sets kthread_should_stop() for @k to return true, wakes it, and
190 * waits for it to exit. Your threadfn() must not call do_exit()
191 * itself if you use this function! This can also be called after
192 * kthread_create() instead of calling wake_up_process(): the thread
193 * will exit without calling threadfn().
194 *
195 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
196 * was never called.
197 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198int kthread_stop(struct task_struct *k)
199{
200 int ret;
201
Arjan van de Ven97d1f152006-03-23 03:00:24 -0800202 mutex_lock(&kthread_stop_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203
204 /* It could exit after stop_info.k set, but before wake_up_process. */
205 get_task_struct(k);
206
Mathieu Desnoyers0a16b602008-07-18 12:16:17 -0400207 trace_sched_kthread_stop(k);
208
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209 /* Must init completion *before* thread sees kthread_stop_info.k */
210 init_completion(&kthread_stop_info.done);
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700211 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212
213 /* Now set kthread_should_stop() to true, and wake it up. */
214 kthread_stop_info.k = k;
Adrian Bunk52e92e52006-07-14 00:24:05 -0700215 wake_up_process(k);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216 put_task_struct(k);
217
218 /* Once it dies, reset stop ptr, gather result and we're done. */
219 wait_for_completion(&kthread_stop_info.done);
220 kthread_stop_info.k = NULL;
221 ret = kthread_stop_info.err;
Arjan van de Ven97d1f152006-03-23 03:00:24 -0800222 mutex_unlock(&kthread_stop_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700223
Mathieu Desnoyers0a16b602008-07-18 12:16:17 -0400224 trace_sched_kthread_stop_ret(ret);
225
Linus Torvalds1da177e2005-04-16 15:20:36 -0700226 return ret;
227}
Adrian Bunk52e92e52006-07-14 00:24:05 -0700228EXPORT_SYMBOL(kthread_stop);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229
Satyam Sharmae804a4a2007-07-31 00:39:16 -0700230int kthreadd(void *unused)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231{
Eric W. Biederman73c27992007-05-09 02:34:32 -0700232 struct task_struct *tsk = current;
Eric W. Biederman73c27992007-05-09 02:34:32 -0700233
Satyam Sharmae804a4a2007-07-31 00:39:16 -0700234 /* Setup a clean context for our children to inherit. */
Eric W. Biederman73c27992007-05-09 02:34:32 -0700235 set_task_comm(tsk, "kthreadd");
Oleg Nesterov10ab8252007-05-09 02:34:37 -0700236 ignore_signals(tsk);
Michal Schmidt4f05b982008-01-25 21:08:33 +0100237 set_user_nice(tsk, KTHREAD_NICE_LEVEL);
Rusty Russell1a2142a2009-03-30 22:05:10 -0600238 set_cpus_allowed_ptr(tsk, cpu_all_mask);
Eric W. Biederman73c27992007-05-09 02:34:32 -0700239
Rafael J. Wysockiebb12db2008-06-11 22:04:29 +0200240 current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
Eric W. Biederman73c27992007-05-09 02:34:32 -0700241
242 for (;;) {
243 set_current_state(TASK_INTERRUPTIBLE);
244 if (list_empty(&kthread_create_list))
245 schedule();
246 __set_current_state(TASK_RUNNING);
247
248 spin_lock(&kthread_create_lock);
249 while (!list_empty(&kthread_create_list)) {
250 struct kthread_create_info *create;
251
252 create = list_entry(kthread_create_list.next,
253 struct kthread_create_info, list);
254 list_del_init(&create->list);
255 spin_unlock(&kthread_create_lock);
256
257 create_kthread(create);
258
259 spin_lock(&kthread_create_lock);
260 }
261 spin_unlock(&kthread_create_lock);
262 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263
264 return 0;
265}