| /* Kernel thread helper functions. |
| * Copyright (C) 2004 IBM Corporation, Rusty Russell. |
| * |
| * Creation is done via kthreadd, 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> |
| |
| #define KTHREAD_NICE_LEVEL (-5) |
| |
| static DEFINE_SPINLOCK(kthread_create_lock); |
| static LIST_HEAD(kthread_create_list); |
| struct task_struct *kthreadd_task; |
| |
| struct kthread_create_info |
| { |
| /* Information passed to kthread() from kthreadd. */ |
| int (*threadfn)(void *data); |
| void *data; |
| struct completion started; |
| |
| /* Result passed back to kthread_create() from kthreadd. */ |
| struct task_struct *result; |
| struct completion done; |
| |
| struct list_head list; |
| }; |
| |
| 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; |
| |
| /** |
| * kthread_should_stop - should this kthread return now? |
| * |
| * When someone calls kthread_stop() on your kthread, it will be woken |
| * and this will return true. You should then return, and your return |
| * value will be passed through to kthread_stop(). |
| */ |
| int kthread_should_stop(void) |
| { |
| return (kthread_stop_info.k == current); |
| } |
| EXPORT_SYMBOL(kthread_should_stop); |
| |
| static int kthread(void *_create) |
| { |
| struct kthread_create_info *create = _create; |
| int (*threadfn)(void *data); |
| void *data; |
| int ret = -EINTR; |
| |
| /* Copy data: it's on kthread's stack */ |
| threadfn = create->threadfn; |
| data = create->data; |
| |
| /* OK, tell user we're spawned, wait for stop or wakeup */ |
| __set_current_state(TASK_UNINTERRUPTIBLE); |
| 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; |
| } |
| |
| static void create_kthread(struct kthread_create_info *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 { |
| struct sched_param param = { .sched_priority = 0 }; |
| wait_for_completion(&create->started); |
| read_lock(&tasklist_lock); |
| create->result = find_task_by_pid_ns(pid, &init_pid_ns); |
| read_unlock(&tasklist_lock); |
| /* |
| * root may have changed our (kthreadd's) priority or CPU mask. |
| * The kernel thread should not inherit these properties. |
| */ |
| sched_setscheduler(create->result, SCHED_NORMAL, ¶m); |
| set_user_nice(create->result, KTHREAD_NICE_LEVEL); |
| set_cpus_allowed(create->result, CPU_MASK_ALL); |
| } |
| complete(&create->done); |
| } |
| |
| /** |
| * kthread_create - create a kthread. |
| * @threadfn: the function to run until signal_pending(current). |
| * @data: data ptr for @threadfn. |
| * @namefmt: printf-style name for the thread. |
| * |
| * Description: This helper function creates and names a kernel |
| * thread. The thread will be stopped: use wake_up_process() to start |
| * it. See also kthread_run(), kthread_create_on_cpu(). |
| * |
| * When woken, the thread will run @threadfn() with @data as its |
| * argument. @threadfn() can either call do_exit() directly if it is a |
| * standalone thread for which noone will call kthread_stop(), or |
| * return when 'kthread_should_stop()' is true (which means |
| * kthread_stop() has been called). The return value should be zero |
| * or a negative error number; it will be passed to kthread_stop(). |
| * |
| * Returns a task_struct or ERR_PTR(-ENOMEM). |
| */ |
| struct task_struct *kthread_create(int (*threadfn)(void *data), |
| void *data, |
| const char namefmt[], |
| ...) |
| { |
| struct kthread_create_info create; |
| |
| create.threadfn = threadfn; |
| create.data = data; |
| init_completion(&create.started); |
| init_completion(&create.done); |
| |
| spin_lock(&kthread_create_lock); |
| list_add_tail(&create.list, &kthread_create_list); |
| spin_unlock(&kthread_create_lock); |
| |
| wake_up_process(kthreadd_task); |
| 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); |
| |
| /** |
| * kthread_bind - bind a just-created kthread to a cpu. |
| * @k: thread created by kthread_create(). |
| * @cpu: cpu (might not be online, must be possible) for @k to run on. |
| * |
| * Description: This function is equivalent to set_cpus_allowed(), |
| * except that @cpu doesn't need to be online, and the thread must be |
| * stopped (i.e., just returned from kthread_create()). |
| */ |
| void kthread_bind(struct task_struct *k, unsigned int cpu) |
| { |
| if (k->state != TASK_UNINTERRUPTIBLE) { |
| WARN_ON(1); |
| return; |
| } |
| /* 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); |
| k->rt.nr_cpus_allowed = 1; |
| k->flags |= PF_THREAD_BOUND; |
| } |
| EXPORT_SYMBOL(kthread_bind); |
| |
| /** |
| * kthread_stop - stop a thread created by kthread_create(). |
| * @k: thread created by kthread_create(). |
| * |
| * Sets kthread_should_stop() for @k to return true, wakes it, and |
| * waits for it to exit. Your threadfn() must not call do_exit() |
| * itself if you use this function! This can also be called after |
| * kthread_create() instead of calling wake_up_process(): the thread |
| * will exit without calling threadfn(). |
| * |
| * Returns the result of threadfn(), or %-EINTR if wake_up_process() |
| * was never called. |
| */ |
| int kthread_stop(struct task_struct *k) |
| { |
| 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; |
| 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); |
| |
| int kthreadd(void *unused) |
| { |
| struct task_struct *tsk = current; |
| |
| /* Setup a clean context for our children to inherit. */ |
| set_task_comm(tsk, "kthreadd"); |
| ignore_signals(tsk); |
| set_user_nice(tsk, KTHREAD_NICE_LEVEL); |
| set_cpus_allowed(tsk, CPU_MASK_ALL); |
| |
| current->flags |= PF_NOFREEZE; |
| |
| for (;;) { |
| set_current_state(TASK_INTERRUPTIBLE); |
| if (list_empty(&kthread_create_list)) |
| schedule(); |
| __set_current_state(TASK_RUNNING); |
| |
| spin_lock(&kthread_create_lock); |
| while (!list_empty(&kthread_create_list)) { |
| struct kthread_create_info *create; |
| |
| create = list_entry(kthread_create_list.next, |
| struct kthread_create_info, list); |
| list_del_init(&create->list); |
| spin_unlock(&kthread_create_lock); |
| |
| create_kthread(create); |
| |
| spin_lock(&kthread_create_lock); |
| } |
| spin_unlock(&kthread_create_lock); |
| } |
| |
| return 0; |
| } |