Merge branch 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc
[linux-2.6/lfs.git] / kernel / kthread.c
blobbd1b9ea024e1238cb230c159c426f3a4f0c8981e
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,
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>
17 #define KTHREAD_NICE_LEVEL (-5)
19 static DEFINE_SPINLOCK(kthread_create_lock);
20 static LIST_HEAD(kthread_create_list);
21 struct task_struct *kthreadd_task;
23 struct kthread_create_info
25 /* Information passed to kthread() from kthreadd. */
26 int (*threadfn)(void *data);
27 void *data;
28 struct completion started;
30 /* Result passed back to kthread_create() from kthreadd. */
31 struct task_struct *result;
32 struct completion done;
34 struct list_head list;
37 struct kthread_stop_info
39 struct task_struct *k;
40 int err;
41 struct completion done;
44 /* Thread stopping is done by setthing this var: lock serializes
45 * multiple kthread_stop calls. */
46 static DEFINE_MUTEX(kthread_stop_lock);
47 static struct kthread_stop_info kthread_stop_info;
49 /**
50 * kthread_should_stop - should this kthread return now?
52 * When someone calls kthread_stop() on your kthread, it will be woken
53 * and this will return true. You should then return, and your return
54 * value will be passed through to kthread_stop().
56 int kthread_should_stop(void)
58 return (kthread_stop_info.k == current);
60 EXPORT_SYMBOL(kthread_should_stop);
62 static int kthread(void *_create)
64 struct kthread_create_info *create = _create;
65 int (*threadfn)(void *data);
66 void *data;
67 int ret = -EINTR;
69 /* Copy data: it's on kthread's stack */
70 threadfn = create->threadfn;
71 data = create->data;
73 /* OK, tell user we're spawned, wait for stop or wakeup */
74 __set_current_state(TASK_UNINTERRUPTIBLE);
75 complete(&create->started);
76 schedule();
78 if (!kthread_should_stop())
79 ret = threadfn(data);
81 /* It might have exited on its own, w/o kthread_stop. Check. */
82 if (kthread_should_stop()) {
83 kthread_stop_info.err = ret;
84 complete(&kthread_stop_info.done);
86 return 0;
89 static void create_kthread(struct kthread_create_info *create)
91 int pid;
93 /* We want our own signal handler (we take no signals by default). */
94 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
95 if (pid < 0) {
96 create->result = ERR_PTR(pid);
97 } else {
98 struct sched_param param = { .sched_priority = 0 };
99 wait_for_completion(&create->started);
100 read_lock(&tasklist_lock);
101 create->result = find_task_by_pid_ns(pid, &init_pid_ns);
102 read_unlock(&tasklist_lock);
104 * root may have changed our (kthreadd's) priority or CPU mask.
105 * The kernel thread should not inherit these properties.
107 sched_setscheduler(create->result, SCHED_NORMAL, &param);
108 set_user_nice(create->result, KTHREAD_NICE_LEVEL);
109 set_cpus_allowed(create->result, CPU_MASK_ALL);
111 complete(&create->done);
115 * kthread_create - create a kthread.
116 * @threadfn: the function to run until signal_pending(current).
117 * @data: data ptr for @threadfn.
118 * @namefmt: printf-style name for the thread.
120 * Description: This helper function creates and names a kernel
121 * thread. The thread will be stopped: use wake_up_process() to start
122 * it. See also kthread_run(), kthread_create_on_cpu().
124 * When woken, the thread will run @threadfn() with @data as its
125 * argument. @threadfn() can either call do_exit() directly if it is a
126 * standalone thread for which noone will call kthread_stop(), or
127 * return when 'kthread_should_stop()' is true (which means
128 * kthread_stop() has been called). The return value should be zero
129 * or a negative error number; it will be passed to kthread_stop().
131 * Returns a task_struct or ERR_PTR(-ENOMEM).
133 struct task_struct *kthread_create(int (*threadfn)(void *data),
134 void *data,
135 const char namefmt[],
136 ...)
138 struct kthread_create_info create;
140 create.threadfn = threadfn;
141 create.data = data;
142 init_completion(&create.started);
143 init_completion(&create.done);
145 spin_lock(&kthread_create_lock);
146 list_add_tail(&create.list, &kthread_create_list);
147 spin_unlock(&kthread_create_lock);
149 wake_up_process(kthreadd_task);
150 wait_for_completion(&create.done);
152 if (!IS_ERR(create.result)) {
153 va_list args;
154 va_start(args, namefmt);
155 vsnprintf(create.result->comm, sizeof(create.result->comm),
156 namefmt, args);
157 va_end(args);
159 return create.result;
161 EXPORT_SYMBOL(kthread_create);
164 * kthread_bind - bind a just-created kthread to a cpu.
165 * @k: thread created by kthread_create().
166 * @cpu: cpu (might not be online, must be possible) for @k to run on.
168 * Description: This function is equivalent to set_cpus_allowed(),
169 * except that @cpu doesn't need to be online, and the thread must be
170 * stopped (i.e., just returned from kthread_create()).
172 void kthread_bind(struct task_struct *k, unsigned int cpu)
174 if (k->state != TASK_UNINTERRUPTIBLE) {
175 WARN_ON(1);
176 return;
178 /* Must have done schedule() in kthread() before we set_task_cpu */
179 wait_task_inactive(k);
180 set_task_cpu(k, cpu);
181 k->cpus_allowed = cpumask_of_cpu(cpu);
182 k->rt.nr_cpus_allowed = 1;
184 EXPORT_SYMBOL(kthread_bind);
187 * kthread_stop - stop a thread created by kthread_create().
188 * @k: thread created by kthread_create().
190 * Sets kthread_should_stop() for @k to return true, wakes it, and
191 * waits for it to exit. Your threadfn() must not call do_exit()
192 * itself if you use this function! This can also be called after
193 * kthread_create() instead of calling wake_up_process(): the thread
194 * will exit without calling threadfn().
196 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
197 * was never called.
199 int kthread_stop(struct task_struct *k)
201 int ret;
203 mutex_lock(&kthread_stop_lock);
205 /* It could exit after stop_info.k set, but before wake_up_process. */
206 get_task_struct(k);
208 /* Must init completion *before* thread sees kthread_stop_info.k */
209 init_completion(&kthread_stop_info.done);
210 smp_wmb();
212 /* Now set kthread_should_stop() to true, and wake it up. */
213 kthread_stop_info.k = k;
214 wake_up_process(k);
215 put_task_struct(k);
217 /* Once it dies, reset stop ptr, gather result and we're done. */
218 wait_for_completion(&kthread_stop_info.done);
219 kthread_stop_info.k = NULL;
220 ret = kthread_stop_info.err;
221 mutex_unlock(&kthread_stop_lock);
223 return ret;
225 EXPORT_SYMBOL(kthread_stop);
227 int kthreadd(void *unused)
229 struct task_struct *tsk = current;
231 /* Setup a clean context for our children to inherit. */
232 set_task_comm(tsk, "kthreadd");
233 ignore_signals(tsk);
234 set_user_nice(tsk, KTHREAD_NICE_LEVEL);
235 set_cpus_allowed(tsk, CPU_MASK_ALL);
237 current->flags |= PF_NOFREEZE;
239 for (;;) {
240 set_current_state(TASK_INTERRUPTIBLE);
241 if (list_empty(&kthread_create_list))
242 schedule();
243 __set_current_state(TASK_RUNNING);
245 spin_lock(&kthread_create_lock);
246 while (!list_empty(&kthread_create_list)) {
247 struct kthread_create_info *create;
249 create = list_entry(kthread_create_list.next,
250 struct kthread_create_info, list);
251 list_del_init(&create->list);
252 spin_unlock(&kthread_create_lock);
254 create_kthread(create);
256 spin_lock(&kthread_create_lock);
258 spin_unlock(&kthread_create_lock);
261 return 0;