| /* 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 <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 { |
| int should_stop; |
| void *data; |
| struct completion exited; |
| }; |
| |
| #define to_kthread(tsk) \ |
| container_of((tsk)->vfork_done, struct kthread, exited) |
| |
| /** |
| * 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 to_kthread(current)->should_stop; |
| } |
| EXPORT_SYMBOL(kthread_should_stop); |
| |
| /** |
| * 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; |
| } |
| |
| 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 kthread self; |
| int ret; |
| |
| self.should_stop = 0; |
| self.data = data; |
| init_completion(&self.exited); |
| current->vfork_done = &self.exited; |
| |
| /* OK, tell user we're spawned, wait for stop or wakeup */ |
| __set_current_state(TASK_UNINTERRUPTIBLE); |
| create->result = current; |
| complete(&create->done); |
| schedule(); |
| |
| ret = -EINTR; |
| if (!self.should_stop) |
| 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_node_id(); |
| } |
| |
| 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) { |
| create->result = ERR_PTR(pid); |
| complete(&create->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). |
| */ |
| struct task_struct *kthread_create_on_node(int (*threadfn)(void *data), |
| void *data, |
| int node, |
| const char namefmt[], |
| ...) |
| { |
| struct kthread_create_info create; |
| |
| create.threadfn = threadfn; |
| create.data = data; |
| create.node = node; |
| 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)) { |
| static const struct sched_param param = { .sched_priority = 0 }; |
| va_list args; |
| |
| va_start(args, namefmt); |
| vsnprintf(create.result->comm, sizeof(create.result->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(create.result, SCHED_NORMAL, ¶m); |
| set_cpus_allowed_ptr(create.result, cpu_all_mask); |
| } |
| return create.result; |
| } |
| EXPORT_SYMBOL(kthread_create_on_node); |
| |
| /** |
| * 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) |
| { |
| /* Must have done schedule() in kthread() before we set_task_cpu */ |
| if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) { |
| WARN_ON(1); |
| return; |
| } |
| |
| /* It's safe because the task is inactive. */ |
| do_set_cpus_allowed(p, cpumask_of(cpu)); |
| p->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. 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_kthread(k); |
| barrier(); /* it might have exited */ |
| if (k->vfork_done != NULL) { |
| kthread->should_stop = 1; |
| 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_HIGH_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); |
| } |
| spin_unlock_irq(&worker->lock); |
| |
| if (work) { |
| __set_current_state(TASK_RUNNING); |
| work->func(work); |
| smp_wmb(); /* wmb worker-b0 paired with flush-b1 */ |
| work->done_seq = work->queue_seq; |
| smp_mb(); /* mb worker-b1 paired with flush-b0 */ |
| if (atomic_read(&work->flushing)) |
| wake_up_all(&work->done); |
| } else if (!freezing(current)) |
| schedule(); |
| |
| try_to_freeze(); |
| goto repeat; |
| } |
| EXPORT_SYMBOL_GPL(kthread_worker_fn); |
| |
| /** |
| * 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)) { |
| list_add_tail(&work->node, &worker->work_list); |
| work->queue_seq++; |
| if (likely(worker->task)) |
| wake_up_process(worker->task); |
| ret = true; |
| } |
| spin_unlock_irqrestore(&worker->lock, flags); |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(queue_kthread_work); |
| |
| /** |
| * 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) |
| { |
| int seq = work->queue_seq; |
| |
| atomic_inc(&work->flushing); |
| |
| /* |
| * mb flush-b0 paired with worker-b1, to make sure either |
| * worker sees the above increment or we see done_seq update. |
| */ |
| smp_mb__after_atomic_inc(); |
| |
| /* A - B <= 0 tests whether B is in front of A regardless of overflow */ |
| wait_event(work->done, seq - work->done_seq <= 0); |
| atomic_dec(&work->flushing); |
| |
| /* |
| * rmb flush-b1 paired with worker-b0, to make sure our caller |
| * sees every change made by work->func(). |
| */ |
| smp_mb__after_atomic_dec(); |
| } |
| EXPORT_SYMBOL_GPL(flush_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_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); |