diff options
| -rw-r--r-- | include/linux/kthread.h | 64 | ||||
| -rw-r--r-- | kernel/kthread.c | 149 |
2 files changed, 213 insertions, 0 deletions
diff --git a/include/linux/kthread.h b/include/linux/kthread.h index aabc8a13ba71..f93cb6979edc 100644 --- a/include/linux/kthread.h +++ b/include/linux/kthread.h @@ -34,4 +34,68 @@ int kthread_should_stop(void); int kthreadd(void *unused); extern struct task_struct *kthreadd_task; +/* + * Simple work processor based on kthread. + * + * This provides easier way to make use of kthreads. A kthread_work + * can be queued and flushed using queue/flush_kthread_work() + * respectively. Queued kthread_works are processed by a kthread + * running kthread_worker_fn(). + * + * A kthread_work can't be freed while it is executing. + */ +struct kthread_work; +typedef void (*kthread_work_func_t)(struct kthread_work *work); + +struct kthread_worker { + spinlock_t lock; + struct list_head work_list; + struct task_struct *task; +}; + +struct kthread_work { + struct list_head node; + kthread_work_func_t func; + wait_queue_head_t done; + atomic_t flushing; + int queue_seq; + int done_seq; +}; + +#define KTHREAD_WORKER_INIT(worker) { \ + .lock = SPIN_LOCK_UNLOCKED, \ + .work_list = LIST_HEAD_INIT((worker).work_list), \ + } + +#define KTHREAD_WORK_INIT(work, fn) { \ + .node = LIST_HEAD_INIT((work).node), \ + .func = (fn), \ + .done = __WAIT_QUEUE_HEAD_INITIALIZER((work).done), \ + .flushing = ATOMIC_INIT(0), \ + } + +#define DEFINE_KTHREAD_WORKER(worker) \ + struct kthread_worker worker = KTHREAD_WORKER_INIT(worker) + +#define DEFINE_KTHREAD_WORK(work, fn) \ + struct kthread_work work = KTHREAD_WORK_INIT(work, fn) + +static inline void init_kthread_worker(struct kthread_worker *worker) +{ + *worker = (struct kthread_worker)KTHREAD_WORKER_INIT(*worker); +} + +static inline void init_kthread_work(struct kthread_work *work, + kthread_work_func_t fn) +{ + *work = (struct kthread_work)KTHREAD_WORK_INIT(*work, fn); +} + +int kthread_worker_fn(void *worker_ptr); + +bool queue_kthread_work(struct kthread_worker *worker, + struct kthread_work *work); +void flush_kthread_work(struct kthread_work *work); +void flush_kthread_worker(struct kthread_worker *worker); + #endif /* _LINUX_KTHREAD_H */ diff --git a/kernel/kthread.c b/kernel/kthread.c index 83911c780175..8b63c7fee73b 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -14,6 +14,8 @@ #include <linux/file.h> #include <linux/module.h> #include <linux/mutex.h> +#include <linux/slab.h> +#include <linux/freezer.h> #include <trace/events/sched.h> static DEFINE_SPINLOCK(kthread_create_lock); @@ -247,3 +249,150 @@ int kthreadd(void *unused) return 0; } + +/** + * 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); |