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 <asm/semaphore.h>
16 struct kthread_create_info
18 /* Information passed to kthread() from keventd. */
19 int (*threadfn)(void *data);
21 struct completion started;
23 /* Result passed back to kthread_create() from keventd. */
24 struct task_struct *result;
25 struct completion done;
28 struct kthread_stop_info
30 struct task_struct *k;
32 struct completion done;
35 /* Thread stopping is done by setthing this var: lock serializes
36 * multiple kthread_stop calls. */
37 static DECLARE_MUTEX(kthread_stop_lock);
38 static struct kthread_stop_info kthread_stop_info;
40 int kthread_should_stop(void)
42 return (kthread_stop_info.k == current);
46 static void kthread_exit_files(void)
49 struct task_struct *tsk = current;
51 exit_fs(tsk); /* current->fs->count--; */
54 atomic_inc(&fs->count);
56 current->files = init_task.files;
57 atomic_inc(&tsk->files->count);
60 static int kthread(void *_create)
62 struct kthread_create_info *create = _create;
63 int (*threadfn)(void *data);
67 cpumask_t mask = CPU_MASK_ALL;
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, mask);
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_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;
148 void kthread_bind(struct task_struct *k, unsigned int cpu)
150 BUG_ON(k->state != TASK_INTERRUPTIBLE);
151 /* Must have done schedule() in kthread() before we set_task_cpu */
152 wait_task_inactive(k);
153 set_task_cpu(k, cpu);
154 k->cpus_allowed = cpumask_of_cpu(cpu);
157 int kthread_stop(struct task_struct *k)
161 down(&kthread_stop_lock);
163 /* It could exit after stop_info.k set, but before wake_up_process. */
166 /* Must init completion *before* thread sees kthread_stop_info.k */
167 init_completion(&kthread_stop_info.done);
170 /* Now set kthread_should_stop() to true, and wake it up. */
171 kthread_stop_info.k = k;
175 /* Once it dies, reset stop ptr, gather result and we're done. */
176 wait_for_completion(&kthread_stop_info.done);
177 kthread_stop_info.k = NULL;
178 ret = kthread_stop_info.err;
179 up(&kthread_stop_lock);