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/* Kernel thread helper functions.
* Copyright (C) 2004 IBM Corporation, Rusty Russell.
*
* Creation is done via keventd, so that we get a clean environment
* even if we're invoked from userspace (think modprobe, hotplug cpu,
* etc.).
*/
#include <linux/sched.h>
#include <linux/kthread.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/unistd.h>
#include <linux/file.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <asm/semaphore.h>
/*
* We dont want to execute off keventd since it might
* hold a semaphore our callers hold too:
*/
static struct workqueue_struct *helper_wq;
struct kthread_create_info
{
/* Information passed to kthread() from keventd. */
int (*threadfn)(void *data);
void *data;
struct completion started;
/* Result passed back to kthread_create() from keventd. */
struct task_struct *result;
struct completion done;
};
struct kthread_stop_info
{
struct task_struct *k;
int err;
struct completion done;
};
/* Thread stopping is done by setthing this var: lock serializes
* multiple kthread_stop calls. */
static DEFINE_MUTEX(kthread_stop_lock);
static struct kthread_stop_info kthread_stop_info;
int kthread_should_stop(void)
{
return (kthread_stop_info.k == current);
}
EXPORT_SYMBOL(kthread_should_stop);
static void kthread_exit_files(void)
{
struct fs_struct *fs;
struct task_struct *tsk = current;
exit_fs(tsk); /* current->fs->count--; */
fs = init_task.fs;
tsk->fs = fs;
atomic_inc(&fs->count);
exit_files(tsk);
current->files = init_task.files;
atomic_inc(&tsk->files->count);
}
static int kthread(void *_create)
{
struct kthread_create_info *create = _create;
int (*threadfn)(void *data);
void *data;
sigset_t blocked;
int ret = -EINTR;
kthread_exit_files();
/* Copy data: it's on keventd's stack */
threadfn = create->threadfn;
data = create->data;
/* Block and flush all signals (in case we're not from keventd). */
sigfillset(&blocked);
sigprocmask(SIG_BLOCK, &blocked, NULL);
flush_signals(current);
/* By default we can run anywhere, unlike keventd. */
set_cpus_allowed(current, CPU_MASK_ALL);
/* OK, tell user we're spawned, wait for stop or wakeup */
__set_current_state(TASK_INTERRUPTIBLE);
complete(&create->started);
schedule();
if (!kthread_should_stop())
ret = threadfn(data);
/* It might have exited on its own, w/o kthread_stop. Check. */
if (kthread_should_stop()) {
kthread_stop_info.err = ret;
complete(&kthread_stop_info.done);
}
return 0;
}
/* We are keventd: create a thread. */
static void keventd_create_kthread(void *_create)
{
struct kthread_create_info *create = _create;
int pid;
/* We want our own signal handler (we take no signals by default). */
pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
if (pid < 0) {
create->result = ERR_PTR(pid);
} else {
wait_for_completion(&create->started);
read_lock(&tasklist_lock);
create->result = find_task_by_pid(pid);
read_unlock(&tasklist_lock);
}
complete(&create->done);
}
struct task_struct *kthread_create(int (*threadfn)(void *data),
void *data,
const char namefmt[],
...)
{
struct kthread_create_info create;
DECLARE_WORK(work, keventd_create_kthread, &create);
create.threadfn = threadfn;
create.data = data;
init_completion(&create.started);
init_completion(&create.done);
/*
* The workqueue needs to start up first:
*/
if (!helper_wq)
work.func(work.data);
else {
queue_work(helper_wq, &work);
wait_for_completion(&create.done);
}
if (!IS_ERR(create.result)) {
va_list args;
va_start(args, namefmt);
vsnprintf(create.result->comm, sizeof(create.result->comm),
namefmt, args);
va_end(args);
}
return create.result;
}
EXPORT_SYMBOL(kthread_create);
void kthread_bind(struct task_struct *k, unsigned int cpu)
{
BUG_ON(k->state != TASK_INTERRUPTIBLE);
/* Must have done schedule() in kthread() before we set_task_cpu */
wait_task_inactive(k);
set_task_cpu(k, cpu);
k->cpus_allowed = cpumask_of_cpu(cpu);
}
EXPORT_SYMBOL(kthread_bind);
int kthread_stop(struct task_struct *k)
{
return kthread_stop_sem(k, NULL);
}
EXPORT_SYMBOL(kthread_stop);
int kthread_stop_sem(struct task_struct *k, struct semaphore *s)
{
int ret;
mutex_lock(&kthread_stop_lock);
/* It could exit after stop_info.k set, but before wake_up_process. */
get_task_struct(k);
/* Must init completion *before* thread sees kthread_stop_info.k */
init_completion(&kthread_stop_info.done);
smp_wmb();
/* Now set kthread_should_stop() to true, and wake it up. */
kthread_stop_info.k = k;
if (s)
up(s);
else
wake_up_process(k);
put_task_struct(k);
/* Once it dies, reset stop ptr, gather result and we're done. */
wait_for_completion(&kthread_stop_info.done);
kthread_stop_info.k = NULL;
ret = kthread_stop_info.err;
mutex_unlock(&kthread_stop_lock);
return ret;
}
EXPORT_SYMBOL(kthread_stop_sem);
static __init int helper_init(void)
{
helper_wq = create_singlethread_workqueue("kthread");
BUG_ON(!helper_wq);
return 0;
}
core_initcall(helper_init);
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