diff options
| -rw-r--r-- | include/linux/kthread.h | 5 | ||||
| -rw-r--r-- | kernel/kthread.c | 132 |
2 files changed, 135 insertions, 2 deletions
diff --git a/include/linux/kthread.h b/include/linux/kthread.h index 4acde1ae2228..77435dcde707 100644 --- a/include/linux/kthread.h +++ b/include/linux/kthread.h @@ -77,6 +77,8 @@ struct kthread_work { struct list_head node; kthread_work_func_t func; struct kthread_worker *worker; + /* Number of canceling calls that are running at the moment. */ + int canceling; }; struct kthread_delayed_work { @@ -169,6 +171,9 @@ bool kthread_queue_delayed_work(struct kthread_worker *worker, void kthread_flush_work(struct kthread_work *work); void kthread_flush_worker(struct kthread_worker *worker); +bool kthread_cancel_work_sync(struct kthread_work *work); +bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *work); + void kthread_destroy_worker(struct kthread_worker *worker); #endif /* _LINUX_KTHREAD_H */ diff --git a/kernel/kthread.c b/kernel/kthread.c index a5c6d709349d..20505c632bc3 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -718,6 +718,19 @@ kthread_create_worker_on_cpu(int cpu, const char namefmt[], ...) } EXPORT_SYMBOL(kthread_create_worker_on_cpu); +/* + * Returns true when the work could not be queued at the moment. + * It happens when it is already pending in a worker list + * or when it is being cancelled. + */ +static inline bool queuing_blocked(struct kthread_worker *worker, + struct kthread_work *work) +{ + lockdep_assert_held(&worker->lock); + + return !list_empty(&work->node) || work->canceling; +} + static void kthread_insert_work_sanity_check(struct kthread_worker *worker, struct kthread_work *work) { @@ -759,7 +772,7 @@ bool kthread_queue_work(struct kthread_worker *worker, unsigned long flags; spin_lock_irqsave(&worker->lock, flags); - if (list_empty(&work->node)) { + if (!queuing_blocked(worker, work)) { kthread_insert_work(worker, work, &worker->work_list); ret = true; } @@ -859,7 +872,7 @@ bool kthread_queue_delayed_work(struct kthread_worker *worker, spin_lock_irqsave(&worker->lock, flags); - if (list_empty(&work->node)) { + if (!queuing_blocked(worker, work)) { __kthread_queue_delayed_work(worker, dwork, delay); ret = true; } @@ -919,6 +932,121 @@ void kthread_flush_work(struct kthread_work *work) } EXPORT_SYMBOL_GPL(kthread_flush_work); +/* + * This function removes the work from the worker queue. Also it makes sure + * that it won't get queued later via the delayed work's timer. + * + * The work might still be in use when this function finishes. See the + * current_work proceed by the worker. + * + * Return: %true if @work was pending and successfully canceled, + * %false if @work was not pending + */ +static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork, + unsigned long *flags) +{ + /* Try to cancel the timer if exists. */ + if (is_dwork) { + struct kthread_delayed_work *dwork = + container_of(work, struct kthread_delayed_work, work); + struct kthread_worker *worker = work->worker; + + /* + * del_timer_sync() must be called to make sure that the timer + * callback is not running. The lock must be temporary released + * to avoid a deadlock with the callback. In the meantime, + * any queuing is blocked by setting the canceling counter. + */ + work->canceling++; + spin_unlock_irqrestore(&worker->lock, *flags); + del_timer_sync(&dwork->timer); + spin_lock_irqsave(&worker->lock, *flags); + work->canceling--; + } + + /* + * Try to remove the work from a worker list. It might either + * be from worker->work_list or from worker->delayed_work_list. + */ + if (!list_empty(&work->node)) { + list_del_init(&work->node); + return true; + } + + return false; +} + +static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork) +{ + struct kthread_worker *worker = work->worker; + unsigned long flags; + int ret = false; + + if (!worker) + goto out; + + spin_lock_irqsave(&worker->lock, flags); + /* Work must not be used with >1 worker, see kthread_queue_work(). */ + WARN_ON_ONCE(work->worker != worker); + + ret = __kthread_cancel_work(work, is_dwork, &flags); + + if (worker->current_work != work) + goto out_fast; + + /* + * The work is in progress and we need to wait with the lock released. + * In the meantime, block any queuing by setting the canceling counter. + */ + work->canceling++; + spin_unlock_irqrestore(&worker->lock, flags); + kthread_flush_work(work); + spin_lock_irqsave(&worker->lock, flags); + work->canceling--; + +out_fast: + spin_unlock_irqrestore(&worker->lock, flags); +out: + return ret; +} + +/** + * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish + * @work: the kthread work to cancel + * + * Cancel @work and wait for its execution to finish. This function + * can be used even if the work re-queues itself. On return from this + * function, @work is guaranteed to be not pending or executing on any CPU. + * + * kthread_cancel_work_sync(&delayed_work->work) must not be used for + * delayed_work's. Use kthread_cancel_delayed_work_sync() instead. + * + * The caller must ensure that the worker on which @work was last + * queued can't be destroyed before this function returns. + * + * Return: %true if @work was pending, %false otherwise. + */ +bool kthread_cancel_work_sync(struct kthread_work *work) +{ + return __kthread_cancel_work_sync(work, false); +} +EXPORT_SYMBOL_GPL(kthread_cancel_work_sync); + +/** + * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and + * wait for it to finish. + * @dwork: the kthread delayed work to cancel + * + * This is kthread_cancel_work_sync() for delayed works. + * + * Return: %true if @dwork was pending, %false otherwise. + */ +bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork) +{ + return __kthread_cancel_work_sync(&dwork->work, true); +} +EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync); + /** * kthread_flush_worker - flush all current works on a kthread_worker * @worker: worker to flush |