1 /* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
4 * Creation is done via keventd, 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/unistd.h>
13 #include <linux/file.h>
14 #include <linux/module.h>
15 #include <asm/semaphore.h>
17 struct kthread_create_info
19 /* Information passed to kthread() from keventd. */
20 int (*threadfn)(void *data);
22 struct completion started;
24 /* Result passed back to kthread_create() from keventd. */
25 struct task_struct *result;
26 struct completion done;
29 struct kthread_stop_info
31 struct task_struct *k;
33 struct completion done;
36 /* Thread stopping is done by setthing this var: lock serializes
37 * multiple kthread_stop calls. */
38 static DECLARE_MUTEX(kthread_stop_lock);
39 static struct kthread_stop_info kthread_stop_info;
41 int kthread_should_stop(void)
43 return (kthread_stop_info.k == current);
45 EXPORT_SYMBOL(kthread_should_stop);
47 static void kthread_exit_files(void)
50 struct task_struct *tsk = current;
52 exit_fs(tsk); /* current->fs->count--; */
55 atomic_inc(&fs->count);
57 current->files = init_task.files;
58 atomic_inc(&tsk->files->count);
61 static int kthread(void *_create)
63 struct kthread_create_info *create = _create;
64 int (*threadfn)(void *data);
71 /* Copy data: it's on keventd's stack */
72 threadfn = create->threadfn;
75 /* Block and flush all signals (in case we're not from keventd). */
77 sigprocmask(SIG_BLOCK, &blocked, NULL);
78 flush_signals(current);
80 /* By default we can run anywhere, unlike keventd. */
81 set_cpus_allowed(current, CPU_MASK_ALL);
83 /* OK, tell user we're spawned, wait for stop or wakeup */
84 __set_current_state(TASK_INTERRUPTIBLE);
85 complete(&create->started);
88 if (!kthread_should_stop())
91 /* It might have exited on its own, w/o kthread_stop. Check. */
92 if (kthread_should_stop()) {
93 kthread_stop_info.err = ret;
94 complete(&kthread_stop_info.done);
99 /* We are keventd: create a thread. */
100 static void keventd_create_kthread(void *_create)
102 struct kthread_create_info *create = _create;
105 /* We want our own signal handler (we take no signals by default). */
106 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
108 create->result = ERR_PTR(pid);
110 wait_for_completion(&create->started);
111 create->result = find_task_by_real_pid(pid);
113 complete(&create->done);
116 struct task_struct *kthread_create(int (*threadfn)(void *data),
118 const char namefmt[],
121 struct kthread_create_info create;
122 DECLARE_WORK(work, keventd_create_kthread, &create);
124 create.threadfn = threadfn;
126 init_completion(&create.started);
127 init_completion(&create.done);
129 /* If we're being called to start the first workqueue, we
130 * can't use keventd. */
132 work.func(work.data);
134 schedule_work(&work);
135 wait_for_completion(&create.done);
137 if (!IS_ERR(create.result)) {
139 va_start(args, namefmt);
140 vsnprintf(create.result->comm, sizeof(create.result->comm),
145 return create.result;
147 EXPORT_SYMBOL(kthread_create);
149 void kthread_bind(struct task_struct *k, unsigned int cpu)
151 BUG_ON(k->state != TASK_INTERRUPTIBLE);
152 /* Must have done schedule() in kthread() before we set_task_cpu */
153 wait_task_inactive(k);
154 set_task_cpu(k, cpu);
155 k->cpus_allowed = cpumask_of_cpu(cpu);
157 EXPORT_SYMBOL(kthread_bind);
159 int kthread_stop(struct task_struct *k)
163 down(&kthread_stop_lock);
165 /* It could exit after stop_info.k set, but before wake_up_process. */
168 /* Must init completion *before* thread sees kthread_stop_info.k */
169 init_completion(&kthread_stop_info.done);
172 /* Now set kthread_should_stop() to true, and wake it up. */
173 kthread_stop_info.k = k;
177 /* Once it dies, reset stop ptr, gather result and we're done. */
178 wait_for_completion(&kthread_stop_info.done);
179 kthread_stop_info.k = NULL;
180 ret = kthread_stop_info.err;
181 up(&kthread_stop_lock);
185 EXPORT_SYMBOL(kthread_stop);