diff options
Diffstat (limited to 'kernel/kthread.c')
| -rw-r--r-- | kernel/kthread.c | 577 |
1 files changed, 507 insertions, 70 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c index 4ab4c3766a80..be2cc1f9dd57 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -138,7 +138,7 @@ void *kthread_data(struct task_struct *task) } /** - * probe_kthread_data - speculative version of kthread_data() + * kthread_probe_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 @@ -146,7 +146,7 @@ void *kthread_data(struct task_struct *task) * 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) +void *kthread_probe_data(struct task_struct *task) { struct kthread *kthread = to_kthread(task); void *data = NULL; @@ -244,33 +244,10 @@ static void create_kthread(struct kthread_create_info *create) } } -/** - * kthread_create_on_node - create a kthread. - * @threadfn: the function to run until signal_pending(current). - * @data: data ptr for @threadfn. - * @node: task and thread structures for the thread are allocated on this node - * @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(). The new thread has SCHED_NORMAL policy and - * is affine to all CPUs. - * - * 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 NUMA_NO_NODE. - * 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[], - ...) +static struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data), + void *data, int node, + const char namefmt[], + va_list args) { DECLARE_COMPLETION_ONSTACK(done); struct task_struct *task; @@ -311,11 +288,8 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data), 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. @@ -326,6 +300,44 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data), kfree(create); return task; } + +/** + * kthread_create_on_node - create a kthread. + * @threadfn: the function to run until signal_pending(current). + * @data: data ptr for @threadfn. + * @node: task and thread structures for the thread are allocated on this node + * @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(). The new thread has SCHED_NORMAL policy and + * is affine to all CPUs. + * + * 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 NUMA_NO_NODE. + * 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[], + ...) +{ + struct task_struct *task; + va_list args; + + va_start(args, namefmt); + task = __kthread_create_on_node(threadfn, data, node, namefmt, args); + va_end(args); + + return task; +} EXPORT_SYMBOL(kthread_create_on_node); static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state) @@ -390,10 +402,10 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data), cpu); if (IS_ERR(p)) return p; + kthread_bind(p, cpu); + /* CPU hotplug need to bind once again when unparking the thread. */ 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; } @@ -407,6 +419,10 @@ static void __kthread_unpark(struct task_struct *k, struct kthread *kthread) * which might be about to be cleared. */ if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) { + /* + * Newly created kthread was parked when the CPU was offline. + * The binding was lost and we need to set it again. + */ if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags)) __kthread_bind(k, kthread->cpu, TASK_PARKED); wake_up_state(k, TASK_PARKED); @@ -540,39 +556,48 @@ int kthreadd(void *unused) return 0; } -void __init_kthread_worker(struct kthread_worker *worker, +void __kthread_init_worker(struct kthread_worker *worker, const char *name, struct lock_class_key *key) { + memset(worker, 0, sizeof(struct kthread_worker)); spin_lock_init(&worker->lock); lockdep_set_class_and_name(&worker->lock, key, name); INIT_LIST_HEAD(&worker->work_list); - worker->task = NULL; + INIT_LIST_HEAD(&worker->delayed_work_list); } -EXPORT_SYMBOL_GPL(__init_kthread_worker); +EXPORT_SYMBOL_GPL(__kthread_init_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. + * This function implements the main cycle of kthread worker. It processes + * work_list until it is stopped with kthread_stop(). It sleeps when the queue + * is empty. + * + * The works are not allowed to keep any locks, disable preemption or interrupts + * when they finish. There is defined a safe point for freezing when one work + * finishes and before a new one is started. * - * 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. + * Also the works must not be handled by more than one worker at the same time, + * see also kthread_queue_work(). */ int kthread_worker_fn(void *worker_ptr) { struct kthread_worker *worker = worker_ptr; struct kthread_work *work; - WARN_ON(worker->task); + /* + * FIXME: Update the check and remove the assignment when all kthread + * worker users are created using kthread_create_worker*() functions. + */ + WARN_ON(worker->task && worker->task != current); worker->task = current; + + if (worker->flags & KTW_FREEZABLE) + set_freezable(); + repeat: set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */ @@ -605,12 +630,131 @@ 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) +static struct kthread_worker * +__kthread_create_worker(int cpu, unsigned int flags, + const char namefmt[], va_list args) +{ + struct kthread_worker *worker; + struct task_struct *task; + + worker = kzalloc(sizeof(*worker), GFP_KERNEL); + if (!worker) + return ERR_PTR(-ENOMEM); + + kthread_init_worker(worker); + + if (cpu >= 0) { + char name[TASK_COMM_LEN]; + + /* + * kthread_create_worker_on_cpu() allows to pass a generic + * namefmt in compare with kthread_create_on_cpu. We need + * to format it here. + */ + vsnprintf(name, sizeof(name), namefmt, args); + task = kthread_create_on_cpu(kthread_worker_fn, worker, + cpu, name); + } else { + task = __kthread_create_on_node(kthread_worker_fn, worker, + -1, namefmt, args); + } + + if (IS_ERR(task)) + goto fail_task; + + worker->flags = flags; + worker->task = task; + wake_up_process(task); + return worker; + +fail_task: + kfree(worker); + return ERR_CAST(task); +} + +/** + * kthread_create_worker - create a kthread worker + * @flags: flags modifying the default behavior of the worker + * @namefmt: printf-style name for the kthread worker (task). + * + * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM) + * when the needed structures could not get allocated, and ERR_PTR(-EINTR) + * when the worker was SIGKILLed. + */ +struct kthread_worker * +kthread_create_worker(unsigned int flags, const char namefmt[], ...) +{ + struct kthread_worker *worker; + va_list args; + + va_start(args, namefmt); + worker = __kthread_create_worker(-1, flags, namefmt, args); + va_end(args); + + return worker; +} +EXPORT_SYMBOL(kthread_create_worker); + +/** + * kthread_create_worker_on_cpu - create a kthread worker and bind it + * it to a given CPU and the associated NUMA node. + * @cpu: CPU number + * @flags: flags modifying the default behavior of the worker + * @namefmt: printf-style name for the kthread worker (task). + * + * Use a valid CPU number if you want to bind the kthread worker + * to the given CPU and the associated NUMA node. + * + * A good practice is to add the cpu number also into the worker name. + * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu). + * + * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM) + * when the needed structures could not get allocated, and ERR_PTR(-EINTR) + * when the worker was SIGKILLed. + */ +struct kthread_worker * +kthread_create_worker_on_cpu(int cpu, unsigned int flags, + const char namefmt[], ...) +{ + struct kthread_worker *worker; + va_list args; + + va_start(args, namefmt); + worker = __kthread_create_worker(cpu, flags, namefmt, args); + va_end(args); + + return worker; +} +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) { lockdep_assert_held(&worker->lock); + WARN_ON_ONCE(!list_empty(&work->node)); + /* Do not use a work with >1 worker, see kthread_queue_work() */ + WARN_ON_ONCE(work->worker && work->worker != worker); +} + +/* insert @work before @pos in @worker */ +static void kthread_insert_work(struct kthread_worker *worker, + struct kthread_work *work, + struct list_head *pos) +{ + kthread_insert_work_sanity_check(worker, work); list_add_tail(&work->node, pos); work->worker = worker; @@ -619,29 +763,133 @@ static void insert_kthread_work(struct kthread_worker *worker, } /** - * queue_kthread_work - queue a kthread_work + * kthread_queue_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. + * + * Reinitialize the work if it needs to be used by another worker. + * For example, when the worker was stopped and started again. */ -bool queue_kthread_work(struct kthread_worker *worker, +bool kthread_queue_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); + if (!queuing_blocked(worker, work)) { + kthread_insert_work(worker, work, &worker->work_list); + ret = true; + } + spin_unlock_irqrestore(&worker->lock, flags); + return ret; +} +EXPORT_SYMBOL_GPL(kthread_queue_work); + +/** + * kthread_delayed_work_timer_fn - callback that queues the associated kthread + * delayed work when the timer expires. + * @__data: pointer to the data associated with the timer + * + * The format of the function is defined by struct timer_list. + * It should have been called from irqsafe timer with irq already off. + */ +void kthread_delayed_work_timer_fn(unsigned long __data) +{ + struct kthread_delayed_work *dwork = + (struct kthread_delayed_work *)__data; + struct kthread_work *work = &dwork->work; + struct kthread_worker *worker = work->worker; + + /* + * This might happen when a pending work is reinitialized. + * It means that it is used a wrong way. + */ + if (WARN_ON_ONCE(!worker)) + return; + + spin_lock(&worker->lock); + /* Work must not be used with >1 worker, see kthread_queue_work(). */ + WARN_ON_ONCE(work->worker != worker); + + /* Move the work from worker->delayed_work_list. */ + WARN_ON_ONCE(list_empty(&work->node)); + list_del_init(&work->node); + kthread_insert_work(worker, work, &worker->work_list); + + spin_unlock(&worker->lock); +} +EXPORT_SYMBOL(kthread_delayed_work_timer_fn); + +void __kthread_queue_delayed_work(struct kthread_worker *worker, + struct kthread_delayed_work *dwork, + unsigned long delay) +{ + struct timer_list *timer = &dwork->timer; + struct kthread_work *work = &dwork->work; + + WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn || + timer->data != (unsigned long)dwork); + + /* + * If @delay is 0, queue @dwork->work immediately. This is for + * both optimization and correctness. The earliest @timer can + * expire is on the closest next tick and delayed_work users depend + * on that there's no such delay when @delay is 0. + */ + if (!delay) { + kthread_insert_work(worker, work, &worker->work_list); + return; + } + + /* Be paranoid and try to detect possible races already now. */ + kthread_insert_work_sanity_check(worker, work); + + list_add(&work->node, &worker->delayed_work_list); + work->worker = worker; + timer_stats_timer_set_start_info(&dwork->timer); + timer->expires = jiffies + delay; + add_timer(timer); +} + +/** + * kthread_queue_delayed_work - queue the associated kthread work + * after a delay. + * @worker: target kthread_worker + * @dwork: kthread_delayed_work to queue + * @delay: number of jiffies to wait before queuing + * + * If the work has not been pending it starts a timer that will queue + * the work after the given @delay. If @delay is zero, it queues the + * work immediately. + * + * Return: %false if the @work has already been pending. It means that + * either the timer was running or the work was queued. It returns %true + * otherwise. + */ +bool kthread_queue_delayed_work(struct kthread_worker *worker, + struct kthread_delayed_work *dwork, + unsigned long delay) +{ + struct kthread_work *work = &dwork->work; + unsigned long flags; + bool ret = false; + + spin_lock_irqsave(&worker->lock, flags); + + if (!queuing_blocked(worker, work)) { + __kthread_queue_delayed_work(worker, dwork, delay); ret = true; } + spin_unlock_irqrestore(&worker->lock, flags); return ret; } -EXPORT_SYMBOL_GPL(queue_kthread_work); +EXPORT_SYMBOL_GPL(kthread_queue_delayed_work); struct kthread_flush_work { struct kthread_work work; @@ -656,12 +904,12 @@ static void kthread_flush_work_fn(struct kthread_work *work) } /** - * flush_kthread_work - flush a kthread_work + * kthread_flush_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) +void kthread_flush_work(struct kthread_work *work) { struct kthread_flush_work fwork = { KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), @@ -670,21 +918,19 @@ void flush_kthread_work(struct kthread_work *work) 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; - } + /* Work must not be used with >1 worker, see kthread_queue_work(). */ + WARN_ON_ONCE(work->worker != worker); if (!list_empty(&work->node)) - insert_kthread_work(worker, &fwork.work, work->node.next); + kthread_insert_work(worker, &fwork.work, work->node.next); else if (worker->current_work == work) - insert_kthread_work(worker, &fwork.work, worker->work_list.next); + kthread_insert_work(worker, &fwork.work, + worker->work_list.next); else noop = true; @@ -693,23 +939,214 @@ retry: if (!noop) wait_for_completion(&fwork.done); } -EXPORT_SYMBOL_GPL(flush_kthread_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; +} + +/** + * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work + * @worker: kthread worker to use + * @dwork: kthread delayed work to queue + * @delay: number of jiffies to wait before queuing + * + * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise, + * modify @dwork's timer so that it expires after @delay. If @delay is zero, + * @work is guaranteed to be queued immediately. + * + * Return: %true if @dwork was pending and its timer was modified, + * %false otherwise. + * + * A special case is when the work is being canceled in parallel. + * It might be caused either by the real kthread_cancel_delayed_work_sync() + * or yet another kthread_mod_delayed_work() call. We let the other command + * win and return %false here. The caller is supposed to synchronize these + * operations a reasonable way. + * + * This function is safe to call from any context including IRQ handler. + * See __kthread_cancel_work() and kthread_delayed_work_timer_fn() + * for details. + */ +bool kthread_mod_delayed_work(struct kthread_worker *worker, + struct kthread_delayed_work *dwork, + unsigned long delay) +{ + struct kthread_work *work = &dwork->work; + unsigned long flags; + int ret = false; + + spin_lock_irqsave(&worker->lock, flags); + + /* Do not bother with canceling when never queued. */ + if (!work->worker) + goto fast_queue; + + /* Work must not be used with >1 worker, see kthread_queue_work() */ + WARN_ON_ONCE(work->worker != worker); + + /* Do not fight with another command that is canceling this work. */ + if (work->canceling) + goto out; + + ret = __kthread_cancel_work(work, true, &flags); +fast_queue: + __kthread_queue_delayed_work(worker, dwork, delay); +out: + spin_unlock_irqrestore(&worker->lock, flags); + return ret; +} +EXPORT_SYMBOL_GPL(kthread_mod_delayed_work); + +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); /** - * flush_kthread_worker - flush all current works on a kthread_worker + * kthread_flush_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) +void kthread_flush_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); + kthread_queue_work(worker, &fwork.work); wait_for_completion(&fwork.done); } -EXPORT_SYMBOL_GPL(flush_kthread_worker); +EXPORT_SYMBOL_GPL(kthread_flush_worker); + +/** + * kthread_destroy_worker - destroy a kthread worker + * @worker: worker to be destroyed + * + * Flush and destroy @worker. The simple flush is enough because the kthread + * worker API is used only in trivial scenarios. There are no multi-step state + * machines needed. + */ +void kthread_destroy_worker(struct kthread_worker *worker) +{ + struct task_struct *task; + + task = worker->task; + if (WARN_ON(!task)) + return; + + kthread_flush_worker(worker); + kthread_stop(task); + WARN_ON(!list_empty(&worker->work_list)); + kfree(worker); +} +EXPORT_SYMBOL(kthread_destroy_worker); |