/* 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_ptr(create->result, CPU_MASK_ALL_PTR); } 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, 0); 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_ptr(tsk, CPU_MASK_ALL_PTR); current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG; 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; }