diff options
Diffstat (limited to 'kernel/kthread.c')
| -rw-r--r-- | kernel/kthread.c | 692 |
1 files changed, 692 insertions, 0 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c new file mode 100644 index 000000000..c4237f12c --- /dev/null +++ b/kernel/kthread.c @@ -0,0 +1,692 @@ +/* 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/cpuset.h> +#include <linux/unistd.h> +#include <linux/file.h> +#include <linux/export.h> +#include <linux/mutex.h> +#include <linux/slab.h> +#include <linux/freezer.h> +#include <linux/ptrace.h> +#include <linux/uaccess.h> +#include <trace/events/sched.h> + +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; + int node; + + /* Result passed back to kthread_create() from kthreadd. */ + struct task_struct *result; + struct completion *done; + + struct list_head list; +}; + +struct kthread { + unsigned long flags; + unsigned int cpu; + void *data; + struct completion parked; + struct completion exited; +}; + +enum KTHREAD_BITS { + KTHREAD_IS_PER_CPU = 0, + KTHREAD_SHOULD_STOP, + KTHREAD_SHOULD_PARK, + KTHREAD_IS_PARKED, +}; + +#define __to_kthread(vfork) \ + container_of(vfork, struct kthread, exited) + +static inline struct kthread *to_kthread(struct task_struct *k) +{ + return __to_kthread(k->vfork_done); +} + +static struct kthread *to_live_kthread(struct task_struct *k) +{ + struct completion *vfork = ACCESS_ONCE(k->vfork_done); + if (likely(vfork)) + return __to_kthread(vfork); + return NULL; +} + +/** + * 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(). + */ +bool kthread_should_stop(void) +{ + return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags); +} +EXPORT_SYMBOL(kthread_should_stop); + +/** + * kthread_should_park - should this kthread park now? + * + * When someone calls kthread_park() on your kthread, it will be woken + * and this will return true. You should then do the necessary + * cleanup and call kthread_parkme() + * + * Similar to kthread_should_stop(), but this keeps the thread alive + * and in a park position. kthread_unpark() "restarts" the thread and + * calls the thread function again. + */ +bool kthread_should_park(void) +{ + return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags); +} + +/** + * kthread_freezable_should_stop - should this freezable kthread return now? + * @was_frozen: optional out parameter, indicates whether %current was frozen + * + * kthread_should_stop() for freezable kthreads, which will enter + * refrigerator if necessary. This function is safe from kthread_stop() / + * freezer deadlock and freezable kthreads should use this function instead + * of calling try_to_freeze() directly. + */ +bool kthread_freezable_should_stop(bool *was_frozen) +{ + bool frozen = false; + + might_sleep(); + + if (unlikely(freezing(current))) + frozen = __refrigerator(true); + + if (was_frozen) + *was_frozen = frozen; + + return kthread_should_stop(); +} +EXPORT_SYMBOL_GPL(kthread_freezable_should_stop); + +/** + * kthread_data - return data value specified on kthread creation + * @task: kthread task in question + * + * Return the data value specified when kthread @task was created. + * The caller is responsible for ensuring the validity of @task when + * calling this function. + */ +void *kthread_data(struct task_struct *task) +{ + return to_kthread(task)->data; +} + +/** + * probe_kthread_data - speculative version of kthread_data() + * @task: possible kthread task in question + * + * @task could be a kthread task. Return the data value specified when it + * was created if accessible. If @task isn't a kthread task or its data is + * inaccessible for any reason, %NULL is returned. This function requires + * that @task itself is safe to dereference. + */ +void *probe_kthread_data(struct task_struct *task) +{ + struct kthread *kthread = to_kthread(task); + void *data = NULL; + + probe_kernel_read(&data, &kthread->data, sizeof(data)); + return data; +} + +static void __kthread_parkme(struct kthread *self) +{ + __set_current_state(TASK_PARKED); + while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) { + if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags)) + complete(&self->parked); + schedule(); + __set_current_state(TASK_PARKED); + } + clear_bit(KTHREAD_IS_PARKED, &self->flags); + __set_current_state(TASK_RUNNING); +} + +void kthread_parkme(void) +{ + __kthread_parkme(to_kthread(current)); +} + +static int kthread(void *_create) +{ + /* Copy data: it's on kthread's stack */ + struct kthread_create_info *create = _create; + int (*threadfn)(void *data) = create->threadfn; + void *data = create->data; + struct completion *done; + struct kthread self; + int ret; + + self.flags = 0; + self.data = data; + init_completion(&self.exited); + init_completion(&self.parked); + current->vfork_done = &self.exited; + + /* If user was SIGKILLed, I release the structure. */ + done = xchg(&create->done, NULL); + if (!done) { + kfree(create); + do_exit(-EINTR); + } + /* OK, tell user we're spawned, wait for stop or wakeup */ + __set_current_state(TASK_UNINTERRUPTIBLE); + create->result = current; + complete(done); + schedule(); + + ret = -EINTR; + + if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) { + __kthread_parkme(&self); + ret = threadfn(data); + } + /* we can't just return, we must preserve "self" on stack */ + do_exit(ret); +} + +/* called from do_fork() to get node information for about to be created task */ +int tsk_fork_get_node(struct task_struct *tsk) +{ +#ifdef CONFIG_NUMA + if (tsk == kthreadd_task) + return tsk->pref_node_fork; +#endif + return NUMA_NO_NODE; +} + +static void create_kthread(struct kthread_create_info *create) +{ + int pid; + +#ifdef CONFIG_NUMA + current->pref_node_fork = create->node; +#endif + /* 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) { + /* If user was SIGKILLed, I release the structure. */ + struct completion *done = xchg(&create->done, NULL); + + if (!done) { + kfree(create); + return; + } + create->result = ERR_PTR(pid); + complete(done); + } +} + +/** + * kthread_create_on_node - create a kthread. + * @threadfn: the function to run until signal_pending(current). + * @data: data ptr for @threadfn. + * @node: memory node number. + * @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(). + * + * If thread is going to be bound on a particular cpu, give its node + * in @node, to get NUMA affinity for kthread stack, or else give -1. + * 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 no one 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) or ERR_PTR(-EINTR). + */ +struct task_struct *kthread_create_on_node(int (*threadfn)(void *data), + void *data, int node, + const char namefmt[], + ...) +{ + DECLARE_COMPLETION_ONSTACK(done); + struct task_struct *task; + struct kthread_create_info *create = kmalloc(sizeof(*create), + GFP_KERNEL | ___GFP_TOI_NOTRACK); + + if (!create) + return ERR_PTR(-ENOMEM); + create->threadfn = threadfn; + create->data = data; + create->node = node; + create->done = &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 in killable state, for I might be chosen by + * the OOM killer while kthreadd is trying to allocate memory for + * new kernel thread. + */ + if (unlikely(wait_for_completion_killable(&done))) { + /* + * If I was SIGKILLed before kthreadd (or new kernel thread) + * calls complete(), leave the cleanup of this structure to + * that thread. + */ + if (xchg(&create->done, NULL)) + return ERR_PTR(-EINTR); + /* + * kthreadd (or new kernel thread) will call complete() + * shortly. + */ + wait_for_completion(&done); + } + task = create->result; + if (!IS_ERR(task)) { + static const struct sched_param param = { .sched_priority = 0 }; + va_list args; + + va_start(args, namefmt); + vsnprintf(task->comm, sizeof(task->comm), namefmt, args); + va_end(args); + /* + * root may have changed our (kthreadd's) priority or CPU mask. + * The kernel thread should not inherit these properties. + */ + sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m); + set_cpus_allowed_ptr(task, cpu_all_mask); + } + kfree(create); + return task; +} +EXPORT_SYMBOL(kthread_create_on_node); + +static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state) +{ + /* Must have done schedule() in kthread() before we set_task_cpu */ + if (!wait_task_inactive(p, state)) { + WARN_ON(1); + return; + } + /* It's safe because the task is inactive. */ + do_set_cpus_allowed(p, cpumask_of(cpu)); + p->flags |= PF_NO_SETAFFINITY; +} + +/** + * kthread_bind - bind a just-created kthread to a cpu. + * @p: 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 *p, unsigned int cpu) +{ + __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE); +} +EXPORT_SYMBOL(kthread_bind); + +/** + * kthread_create_on_cpu - Create a cpu bound kthread + * @threadfn: the function to run until signal_pending(current). + * @data: data ptr for @threadfn. + * @cpu: The cpu on which the thread should be bound, + * @namefmt: printf-style name for the thread. Format is restricted + * to "name.*%u". Code fills in cpu number. + * + * Description: This helper function creates and names a kernel thread + * The thread will be woken and put into park mode. + */ +struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data), + void *data, unsigned int cpu, + const char *namefmt) +{ + struct task_struct *p; + + p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt, + cpu); + if (IS_ERR(p)) + return p; + set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags); + to_kthread(p)->cpu = cpu; + /* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */ + kthread_park(p); + return p; +} + +static void __kthread_unpark(struct task_struct *k, struct kthread *kthread) +{ + clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags); + /* + * We clear the IS_PARKED bit here as we don't wait + * until the task has left the park code. So if we'd + * park before that happens we'd see the IS_PARKED bit + * which might be about to be cleared. + */ + if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) { + if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags)) + __kthread_bind(k, kthread->cpu, TASK_PARKED); + wake_up_state(k, TASK_PARKED); + } +} + +/** + * kthread_unpark - unpark a thread created by kthread_create(). + * @k: thread created by kthread_create(). + * + * Sets kthread_should_park() for @k to return false, wakes it, and + * waits for it to return. If the thread is marked percpu then its + * bound to the cpu again. + */ +void kthread_unpark(struct task_struct *k) +{ + struct kthread *kthread = to_live_kthread(k); + + if (kthread) + __kthread_unpark(k, kthread); +} + +/** + * kthread_park - park a thread created by kthread_create(). + * @k: thread created by kthread_create(). + * + * Sets kthread_should_park() for @k to return true, wakes it, and + * waits for it to return. This can also be called after kthread_create() + * instead of calling wake_up_process(): the thread will park without + * calling threadfn(). + * + * Returns 0 if the thread is parked, -ENOSYS if the thread exited. + * If called by the kthread itself just the park bit is set. + */ +int kthread_park(struct task_struct *k) +{ + struct kthread *kthread = to_live_kthread(k); + int ret = -ENOSYS; + + if (kthread) { + if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) { + set_bit(KTHREAD_SHOULD_PARK, &kthread->flags); + if (k != current) { + wake_up_process(k); + wait_for_completion(&kthread->parked); + } + } + ret = 0; + } + return ret; +} + +/** + * 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. This can also be called after kthread_create() + * instead of calling wake_up_process(): the thread will exit without + * calling threadfn(). + * + * If threadfn() may call do_exit() itself, the caller must ensure + * task_struct can't go away. + * + * Returns the result of threadfn(), or %-EINTR if wake_up_process() + * was never called. + */ +int kthread_stop(struct task_struct *k) +{ + struct kthread *kthread; + int ret; + + trace_sched_kthread_stop(k); + + get_task_struct(k); + kthread = to_live_kthread(k); + if (kthread) { + set_bit(KTHREAD_SHOULD_STOP, &kthread->flags); + __kthread_unpark(k, kthread); + wake_up_process(k); + wait_for_completion(&kthread->exited); + } + ret = k->exit_code; + put_task_struct(k); + + trace_sched_kthread_stop_ret(ret); + 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_cpus_allowed_ptr(tsk, cpu_all_mask); + set_mems_allowed(node_states[N_MEMORY]); + + 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; +} + +void __init_kthread_worker(struct kthread_worker *worker, + const char *name, + struct lock_class_key *key) +{ + spin_lock_init(&worker->lock); + lockdep_set_class_and_name(&worker->lock, key, name); + INIT_LIST_HEAD(&worker->work_list); + worker->task = NULL; +} +EXPORT_SYMBOL_GPL(__init_kthread_worker); + +/** + * kthread_worker_fn - kthread function to process kthread_worker + * @worker_ptr: pointer to initialized kthread_worker + * + * This function can be used as @threadfn to kthread_create() or + * kthread_run() with @worker_ptr argument pointing to an initialized + * kthread_worker. The started kthread will process work_list until + * the it is stopped with kthread_stop(). A kthread can also call + * this function directly after extra initialization. + * + * Different kthreads can be used for the same kthread_worker as long + * as there's only one kthread attached to it at any given time. A + * kthread_worker without an attached kthread simply collects queued + * kthread_works. + */ +int kthread_worker_fn(void *worker_ptr) +{ + struct kthread_worker *worker = worker_ptr; + struct kthread_work *work; + + WARN_ON(worker->task); + worker->task = current; +repeat: + set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */ + + if (kthread_should_stop()) { + __set_current_state(TASK_RUNNING); + spin_lock_irq(&worker->lock); + worker->task = NULL; + spin_unlock_irq(&worker->lock); + return 0; + } + + work = NULL; + spin_lock_irq(&worker->lock); + if (!list_empty(&worker->work_list)) { + work = list_first_entry(&worker->work_list, + struct kthread_work, node); + list_del_init(&work->node); + } + worker->current_work = work; + spin_unlock_irq(&worker->lock); + + if (work) { + __set_current_state(TASK_RUNNING); + work->func(work); + } else if (!freezing(current)) + schedule(); + + try_to_freeze(); + goto repeat; +} +EXPORT_SYMBOL_GPL(kthread_worker_fn); + +/* insert @work before @pos in @worker */ +static void insert_kthread_work(struct kthread_worker *worker, + struct kthread_work *work, + struct list_head *pos) +{ + lockdep_assert_held(&worker->lock); + + list_add_tail(&work->node, pos); + work->worker = worker; + if (!worker->current_work && likely(worker->task)) + wake_up_process(worker->task); +} + +/** + * queue_kthread_work - queue a kthread_work + * @worker: target kthread_worker + * @work: kthread_work to queue + * + * Queue @work to work processor @task for async execution. @task + * must have been created with kthread_worker_create(). Returns %true + * if @work was successfully queued, %false if it was already pending. + */ +bool queue_kthread_work(struct kthread_worker *worker, + struct kthread_work *work) +{ + bool ret = false; + unsigned long flags; + + spin_lock_irqsave(&worker->lock, flags); + if (list_empty(&work->node)) { + insert_kthread_work(worker, work, &worker->work_list); + ret = true; + } + spin_unlock_irqrestore(&worker->lock, flags); + return ret; +} +EXPORT_SYMBOL_GPL(queue_kthread_work); + +struct kthread_flush_work { + struct kthread_work work; + struct completion done; +}; + +static void kthread_flush_work_fn(struct kthread_work *work) +{ + struct kthread_flush_work *fwork = + container_of(work, struct kthread_flush_work, work); + complete(&fwork->done); +} + +/** + * flush_kthread_work - flush a kthread_work + * @work: work to flush + * + * If @work is queued or executing, wait for it to finish execution. + */ +void flush_kthread_work(struct kthread_work *work) +{ + struct kthread_flush_work fwork = { + KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), + COMPLETION_INITIALIZER_ONSTACK(fwork.done), + }; + struct kthread_worker *worker; + bool noop = false; + +retry: + worker = work->worker; + if (!worker) + return; + + spin_lock_irq(&worker->lock); + if (work->worker != worker) { + spin_unlock_irq(&worker->lock); + goto retry; + } + + if (!list_empty(&work->node)) + insert_kthread_work(worker, &fwork.work, work->node.next); + else if (worker->current_work == work) + insert_kthread_work(worker, &fwork.work, worker->work_list.next); + else + noop = true; + + spin_unlock_irq(&worker->lock); + + if (!noop) + wait_for_completion(&fwork.done); +} +EXPORT_SYMBOL_GPL(flush_kthread_work); + +/** + * flush_kthread_worker - flush all current works on a kthread_worker + * @worker: worker to flush + * + * Wait until all currently executing or pending works on @worker are + * finished. + */ +void flush_kthread_worker(struct kthread_worker *worker) +{ + struct kthread_flush_work fwork = { + KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), + COMPLETION_INITIALIZER_ONSTACK(fwork.done), + }; + + queue_kthread_work(worker, &fwork.work); + wait_for_completion(&fwork.done); +} +EXPORT_SYMBOL_GPL(flush_kthread_worker); |