| /* Worker thread pool for slow items, such as filesystem lookups or mkdirs |
| * |
| * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. |
| * Written by David Howells (dhowells@redhat.com) |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public Licence |
| * as published by the Free Software Foundation; either version |
| * 2 of the Licence, or (at your option) any later version. |
| * |
| * See Documentation/slow-work.txt |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/slow-work.h> |
| #include <linux/kthread.h> |
| #include <linux/freezer.h> |
| #include <linux/wait.h> |
| #include <linux/debugfs.h> |
| #include "slow-work.h" |
| |
| static void slow_work_cull_timeout(unsigned long); |
| static void slow_work_oom_timeout(unsigned long); |
| |
| #ifdef CONFIG_SYSCTL |
| static int slow_work_min_threads_sysctl(struct ctl_table *, int, |
| void __user *, size_t *, loff_t *); |
| |
| static int slow_work_max_threads_sysctl(struct ctl_table *, int , |
| void __user *, size_t *, loff_t *); |
| #endif |
| |
| /* |
| * The pool of threads has at least min threads in it as long as someone is |
| * using the facility, and may have as many as max. |
| * |
| * A portion of the pool may be processing very slow operations. |
| */ |
| static unsigned slow_work_min_threads = 2; |
| static unsigned slow_work_max_threads = 4; |
| static unsigned vslow_work_proportion = 50; /* % of threads that may process |
| * very slow work */ |
| |
| #ifdef CONFIG_SYSCTL |
| static const int slow_work_min_min_threads = 2; |
| static int slow_work_max_max_threads = SLOW_WORK_THREAD_LIMIT; |
| static const int slow_work_min_vslow = 1; |
| static const int slow_work_max_vslow = 99; |
| |
| ctl_table slow_work_sysctls[] = { |
| { |
| .procname = "min-threads", |
| .data = &slow_work_min_threads, |
| .maxlen = sizeof(unsigned), |
| .mode = 0644, |
| .proc_handler = slow_work_min_threads_sysctl, |
| .extra1 = (void *) &slow_work_min_min_threads, |
| .extra2 = &slow_work_max_threads, |
| }, |
| { |
| .procname = "max-threads", |
| .data = &slow_work_max_threads, |
| .maxlen = sizeof(unsigned), |
| .mode = 0644, |
| .proc_handler = slow_work_max_threads_sysctl, |
| .extra1 = &slow_work_min_threads, |
| .extra2 = (void *) &slow_work_max_max_threads, |
| }, |
| { |
| .procname = "vslow-percentage", |
| .data = &vslow_work_proportion, |
| .maxlen = sizeof(unsigned), |
| .mode = 0644, |
| .proc_handler = proc_dointvec_minmax, |
| .extra1 = (void *) &slow_work_min_vslow, |
| .extra2 = (void *) &slow_work_max_vslow, |
| }, |
| {} |
| }; |
| #endif |
| |
| /* |
| * The active state of the thread pool |
| */ |
| static atomic_t slow_work_thread_count; |
| static atomic_t vslow_work_executing_count; |
| |
| static bool slow_work_may_not_start_new_thread; |
| static bool slow_work_cull; /* cull a thread due to lack of activity */ |
| static DEFINE_TIMER(slow_work_cull_timer, slow_work_cull_timeout, 0, 0); |
| static DEFINE_TIMER(slow_work_oom_timer, slow_work_oom_timeout, 0, 0); |
| static struct slow_work slow_work_new_thread; /* new thread starter */ |
| |
| /* |
| * slow work ID allocation (use slow_work_queue_lock) |
| */ |
| static DECLARE_BITMAP(slow_work_ids, SLOW_WORK_THREAD_LIMIT); |
| |
| /* |
| * Unregistration tracking to prevent put_ref() from disappearing during module |
| * unload |
| */ |
| #ifdef CONFIG_MODULES |
| static struct module *slow_work_thread_processing[SLOW_WORK_THREAD_LIMIT]; |
| static struct module *slow_work_unreg_module; |
| static struct slow_work *slow_work_unreg_work_item; |
| static DECLARE_WAIT_QUEUE_HEAD(slow_work_unreg_wq); |
| static DEFINE_MUTEX(slow_work_unreg_sync_lock); |
| |
| static void slow_work_set_thread_processing(int id, struct slow_work *work) |
| { |
| if (work) |
| slow_work_thread_processing[id] = work->owner; |
| } |
| static void slow_work_done_thread_processing(int id, struct slow_work *work) |
| { |
| struct module *module = slow_work_thread_processing[id]; |
| |
| slow_work_thread_processing[id] = NULL; |
| smp_mb(); |
| if (slow_work_unreg_work_item == work || |
| slow_work_unreg_module == module) |
| wake_up_all(&slow_work_unreg_wq); |
| } |
| static void slow_work_clear_thread_processing(int id) |
| { |
| slow_work_thread_processing[id] = NULL; |
| } |
| #else |
| static void slow_work_set_thread_processing(int id, struct slow_work *work) {} |
| static void slow_work_done_thread_processing(int id, struct slow_work *work) {} |
| static void slow_work_clear_thread_processing(int id) {} |
| #endif |
| |
| /* |
| * Data for tracking currently executing items for indication through /proc |
| */ |
| #ifdef CONFIG_SLOW_WORK_DEBUG |
| struct slow_work *slow_work_execs[SLOW_WORK_THREAD_LIMIT]; |
| pid_t slow_work_pids[SLOW_WORK_THREAD_LIMIT]; |
| DEFINE_RWLOCK(slow_work_execs_lock); |
| #endif |
| |
| /* |
| * The queues of work items and the lock governing access to them. These are |
| * shared between all the CPUs. It doesn't make sense to have per-CPU queues |
| * as the number of threads bears no relation to the number of CPUs. |
| * |
| * There are two queues of work items: one for slow work items, and one for |
| * very slow work items. |
| */ |
| LIST_HEAD(slow_work_queue); |
| LIST_HEAD(vslow_work_queue); |
| DEFINE_SPINLOCK(slow_work_queue_lock); |
| |
| /* |
| * The following are two wait queues that get pinged when a work item is placed |
| * on an empty queue. These allow work items that are hogging a thread by |
| * sleeping in a way that could be deferred to yield their thread and enqueue |
| * themselves. |
| */ |
| static DECLARE_WAIT_QUEUE_HEAD(slow_work_queue_waits_for_occupation); |
| static DECLARE_WAIT_QUEUE_HEAD(vslow_work_queue_waits_for_occupation); |
| |
| /* |
| * The thread controls. A variable used to signal to the threads that they |
| * should exit when the queue is empty, a waitqueue used by the threads to wait |
| * for signals, and a completion set by the last thread to exit. |
| */ |
| static bool slow_work_threads_should_exit; |
| static DECLARE_WAIT_QUEUE_HEAD(slow_work_thread_wq); |
| static DECLARE_COMPLETION(slow_work_last_thread_exited); |
| |
| /* |
| * The number of users of the thread pool and its lock. Whilst this is zero we |
| * have no threads hanging around, and when this reaches zero, we wait for all |
| * active or queued work items to complete and kill all the threads we do have. |
| */ |
| static int slow_work_user_count; |
| static DEFINE_MUTEX(slow_work_user_lock); |
| |
| static inline int slow_work_get_ref(struct slow_work *work) |
| { |
| if (work->ops->get_ref) |
| return work->ops->get_ref(work); |
| |
| return 0; |
| } |
| |
| static inline void slow_work_put_ref(struct slow_work *work) |
| { |
| if (work->ops->put_ref) |
| work->ops->put_ref(work); |
| } |
| |
| /* |
| * Calculate the maximum number of active threads in the pool that are |
| * permitted to process very slow work items. |
| * |
| * The answer is rounded up to at least 1, but may not equal or exceed the |
| * maximum number of the threads in the pool. This means we always have at |
| * least one thread that can process slow work items, and we always have at |
| * least one thread that won't get tied up doing so. |
| */ |
| static unsigned slow_work_calc_vsmax(void) |
| { |
| unsigned vsmax; |
| |
| vsmax = atomic_read(&slow_work_thread_count) * vslow_work_proportion; |
| vsmax /= 100; |
| vsmax = max(vsmax, 1U); |
| return min(vsmax, slow_work_max_threads - 1); |
| } |
| |
| /* |
| * Attempt to execute stuff queued on a slow thread. Return true if we managed |
| * it, false if there was nothing to do. |
| */ |
| static noinline bool slow_work_execute(int id) |
| { |
| struct slow_work *work = NULL; |
| unsigned vsmax; |
| bool very_slow; |
| |
| vsmax = slow_work_calc_vsmax(); |
| |
| /* see if we can schedule a new thread to be started if we're not |
| * keeping up with the work */ |
| if (!waitqueue_active(&slow_work_thread_wq) && |
| (!list_empty(&slow_work_queue) || !list_empty(&vslow_work_queue)) && |
| atomic_read(&slow_work_thread_count) < slow_work_max_threads && |
| !slow_work_may_not_start_new_thread) |
| slow_work_enqueue(&slow_work_new_thread); |
| |
| /* find something to execute */ |
| spin_lock_irq(&slow_work_queue_lock); |
| if (!list_empty(&vslow_work_queue) && |
| atomic_read(&vslow_work_executing_count) < vsmax) { |
| work = list_entry(vslow_work_queue.next, |
| struct slow_work, link); |
| if (test_and_set_bit_lock(SLOW_WORK_EXECUTING, &work->flags)) |
| BUG(); |
| list_del_init(&work->link); |
| atomic_inc(&vslow_work_executing_count); |
| very_slow = true; |
| } else if (!list_empty(&slow_work_queue)) { |
| work = list_entry(slow_work_queue.next, |
| struct slow_work, link); |
| if (test_and_set_bit_lock(SLOW_WORK_EXECUTING, &work->flags)) |
| BUG(); |
| list_del_init(&work->link); |
| very_slow = false; |
| } else { |
| very_slow = false; /* avoid the compiler warning */ |
| } |
| |
| slow_work_set_thread_processing(id, work); |
| if (work) { |
| slow_work_mark_time(work); |
| slow_work_begin_exec(id, work); |
| } |
| |
| spin_unlock_irq(&slow_work_queue_lock); |
| |
| if (!work) |
| return false; |
| |
| if (!test_and_clear_bit(SLOW_WORK_PENDING, &work->flags)) |
| BUG(); |
| |
| /* don't execute if the work is in the process of being cancelled */ |
| if (!test_bit(SLOW_WORK_CANCELLING, &work->flags)) |
| work->ops->execute(work); |
| |
| if (very_slow) |
| atomic_dec(&vslow_work_executing_count); |
| clear_bit_unlock(SLOW_WORK_EXECUTING, &work->flags); |
| |
| /* wake up anyone waiting for this work to be complete */ |
| wake_up_bit(&work->flags, SLOW_WORK_EXECUTING); |
| |
| slow_work_end_exec(id, work); |
| |
| /* if someone tried to enqueue the item whilst we were executing it, |
| * then it'll be left unenqueued to avoid multiple threads trying to |
| * execute it simultaneously |
| * |
| * there is, however, a race between us testing the pending flag and |
| * getting the spinlock, and between the enqueuer setting the pending |
| * flag and getting the spinlock, so we use a deferral bit to tell us |
| * if the enqueuer got there first |
| */ |
| if (test_bit(SLOW_WORK_PENDING, &work->flags)) { |
| spin_lock_irq(&slow_work_queue_lock); |
| |
| if (!test_bit(SLOW_WORK_EXECUTING, &work->flags) && |
| test_and_clear_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags)) |
| goto auto_requeue; |
| |
| spin_unlock_irq(&slow_work_queue_lock); |
| } |
| |
| /* sort out the race between module unloading and put_ref() */ |
| slow_work_put_ref(work); |
| slow_work_done_thread_processing(id, work); |
| |
| return true; |
| |
| auto_requeue: |
| /* we must complete the enqueue operation |
| * - we transfer our ref on the item back to the appropriate queue |
| * - don't wake another thread up as we're awake already |
| */ |
| slow_work_mark_time(work); |
| if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) |
| list_add_tail(&work->link, &vslow_work_queue); |
| else |
| list_add_tail(&work->link, &slow_work_queue); |
| spin_unlock_irq(&slow_work_queue_lock); |
| slow_work_clear_thread_processing(id); |
| return true; |
| } |
| |
| /** |
| * slow_work_sleep_till_thread_needed - Sleep till thread needed by other work |
| * work: The work item under execution that wants to sleep |
| * _timeout: Scheduler sleep timeout |
| * |
| * Allow a requeueable work item to sleep on a slow-work processor thread until |
| * that thread is needed to do some other work or the sleep is interrupted by |
| * some other event. |
| * |
| * The caller must set up a wake up event before calling this and must have set |
| * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own |
| * condition before calling this function as no test is made here. |
| * |
| * False is returned if there is nothing on the queue; true is returned if the |
| * work item should be requeued |
| */ |
| bool slow_work_sleep_till_thread_needed(struct slow_work *work, |
| signed long *_timeout) |
| { |
| wait_queue_head_t *wfo_wq; |
| struct list_head *queue; |
| |
| DEFINE_WAIT(wait); |
| |
| if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) { |
| wfo_wq = &vslow_work_queue_waits_for_occupation; |
| queue = &vslow_work_queue; |
| } else { |
| wfo_wq = &slow_work_queue_waits_for_occupation; |
| queue = &slow_work_queue; |
| } |
| |
| if (!list_empty(queue)) |
| return true; |
| |
| add_wait_queue_exclusive(wfo_wq, &wait); |
| if (list_empty(queue)) |
| *_timeout = schedule_timeout(*_timeout); |
| finish_wait(wfo_wq, &wait); |
| |
| return !list_empty(queue); |
| } |
| EXPORT_SYMBOL(slow_work_sleep_till_thread_needed); |
| |
| /** |
| * slow_work_enqueue - Schedule a slow work item for processing |
| * @work: The work item to queue |
| * |
| * Schedule a slow work item for processing. If the item is already undergoing |
| * execution, this guarantees not to re-enter the execution routine until the |
| * first execution finishes. |
| * |
| * The item is pinned by this function as it retains a reference to it, managed |
| * through the item operations. The item is unpinned once it has been |
| * executed. |
| * |
| * An item may hog the thread that is running it for a relatively large amount |
| * of time, sufficient, for example, to perform several lookup, mkdir, create |
| * and setxattr operations. It may sleep on I/O and may sleep to obtain locks. |
| * |
| * Conversely, if a number of items are awaiting processing, it may take some |
| * time before any given item is given attention. The number of threads in the |
| * pool may be increased to deal with demand, but only up to a limit. |
| * |
| * If SLOW_WORK_VERY_SLOW is set on the work item, then it will be placed in |
| * the very slow queue, from which only a portion of the threads will be |
| * allowed to pick items to execute. This ensures that very slow items won't |
| * overly block ones that are just ordinarily slow. |
| * |
| * Returns 0 if successful, -EAGAIN if not (or -ECANCELED if cancelled work is |
| * attempted queued) |
| */ |
| int slow_work_enqueue(struct slow_work *work) |
| { |
| wait_queue_head_t *wfo_wq; |
| struct list_head *queue; |
| unsigned long flags; |
| int ret; |
| |
| if (test_bit(SLOW_WORK_CANCELLING, &work->flags)) |
| return -ECANCELED; |
| |
| BUG_ON(slow_work_user_count <= 0); |
| BUG_ON(!work); |
| BUG_ON(!work->ops); |
| |
| /* when honouring an enqueue request, we only promise that we will run |
| * the work function in the future; we do not promise to run it once |
| * per enqueue request |
| * |
| * we use the PENDING bit to merge together repeat requests without |
| * having to disable IRQs and take the spinlock, whilst still |
| * maintaining our promise |
| */ |
| if (!test_and_set_bit_lock(SLOW_WORK_PENDING, &work->flags)) { |
| if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) { |
| wfo_wq = &vslow_work_queue_waits_for_occupation; |
| queue = &vslow_work_queue; |
| } else { |
| wfo_wq = &slow_work_queue_waits_for_occupation; |
| queue = &slow_work_queue; |
| } |
| |
| spin_lock_irqsave(&slow_work_queue_lock, flags); |
| |
| if (unlikely(test_bit(SLOW_WORK_CANCELLING, &work->flags))) |
| goto cancelled; |
| |
| /* we promise that we will not attempt to execute the work |
| * function in more than one thread simultaneously |
| * |
| * this, however, leaves us with a problem if we're asked to |
| * enqueue the work whilst someone is executing the work |
| * function as simply queueing the work immediately means that |
| * another thread may try executing it whilst it is already |
| * under execution |
| * |
| * to deal with this, we set the ENQ_DEFERRED bit instead of |
| * enqueueing, and the thread currently executing the work |
| * function will enqueue the work item when the work function |
| * returns and it has cleared the EXECUTING bit |
| */ |
| if (test_bit(SLOW_WORK_EXECUTING, &work->flags)) { |
| set_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags); |
| } else { |
| ret = slow_work_get_ref(work); |
| if (ret < 0) |
| goto failed; |
| slow_work_mark_time(work); |
| list_add_tail(&work->link, queue); |
| wake_up(&slow_work_thread_wq); |
| |
| /* if someone who could be requeued is sleeping on a |
| * thread, then ask them to yield their thread */ |
| if (work->link.prev == queue) |
| wake_up(wfo_wq); |
| } |
| |
| spin_unlock_irqrestore(&slow_work_queue_lock, flags); |
| } |
| return 0; |
| |
| cancelled: |
| ret = -ECANCELED; |
| failed: |
| spin_unlock_irqrestore(&slow_work_queue_lock, flags); |
| return ret; |
| } |
| EXPORT_SYMBOL(slow_work_enqueue); |
| |
| static int slow_work_wait(void *word) |
| { |
| schedule(); |
| return 0; |
| } |
| |
| /** |
| * slow_work_cancel - Cancel a slow work item |
| * @work: The work item to cancel |
| * |
| * This function will cancel a previously enqueued work item. If we cannot |
| * cancel the work item, it is guarenteed to have run when this function |
| * returns. |
| */ |
| void slow_work_cancel(struct slow_work *work) |
| { |
| bool wait = true, put = false; |
| |
| set_bit(SLOW_WORK_CANCELLING, &work->flags); |
| smp_mb(); |
| |
| /* if the work item is a delayed work item with an active timer, we |
| * need to wait for the timer to finish _before_ getting the spinlock, |
| * lest we deadlock against the timer routine |
| * |
| * the timer routine will leave DELAYED set if it notices the |
| * CANCELLING flag in time |
| */ |
| if (test_bit(SLOW_WORK_DELAYED, &work->flags)) { |
| struct delayed_slow_work *dwork = |
| container_of(work, struct delayed_slow_work, work); |
| del_timer_sync(&dwork->timer); |
| } |
| |
| spin_lock_irq(&slow_work_queue_lock); |
| |
| if (test_bit(SLOW_WORK_DELAYED, &work->flags)) { |
| /* the timer routine aborted or never happened, so we are left |
| * holding the timer's reference on the item and should just |
| * drop the pending flag and wait for any ongoing execution to |
| * finish */ |
| struct delayed_slow_work *dwork = |
| container_of(work, struct delayed_slow_work, work); |
| |
| BUG_ON(timer_pending(&dwork->timer)); |
| BUG_ON(!list_empty(&work->link)); |
| |
| clear_bit(SLOW_WORK_DELAYED, &work->flags); |
| put = true; |
| clear_bit(SLOW_WORK_PENDING, &work->flags); |
| |
| } else if (test_bit(SLOW_WORK_PENDING, &work->flags) && |
| !list_empty(&work->link)) { |
| /* the link in the pending queue holds a reference on the item |
| * that we will need to release */ |
| list_del_init(&work->link); |
| wait = false; |
| put = true; |
| clear_bit(SLOW_WORK_PENDING, &work->flags); |
| |
| } else if (test_and_clear_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags)) { |
| /* the executor is holding our only reference on the item, so |
| * we merely need to wait for it to finish executing */ |
| clear_bit(SLOW_WORK_PENDING, &work->flags); |
| } |
| |
| spin_unlock_irq(&slow_work_queue_lock); |
| |
| /* the EXECUTING flag is set by the executor whilst the spinlock is set |
| * and before the item is dequeued - so assuming the above doesn't |
| * actually dequeue it, simply waiting for the EXECUTING flag to be |
| * released here should be sufficient */ |
| if (wait) |
| wait_on_bit(&work->flags, SLOW_WORK_EXECUTING, slow_work_wait, |
| TASK_UNINTERRUPTIBLE); |
| |
| clear_bit(SLOW_WORK_CANCELLING, &work->flags); |
| if (put) |
| slow_work_put_ref(work); |
| } |
| EXPORT_SYMBOL(slow_work_cancel); |
| |
| /* |
| * Handle expiry of the delay timer, indicating that a delayed slow work item |
| * should now be queued if not cancelled |
| */ |
| static void delayed_slow_work_timer(unsigned long data) |
| { |
| wait_queue_head_t *wfo_wq; |
| struct list_head *queue; |
| struct slow_work *work = (struct slow_work *) data; |
| unsigned long flags; |
| bool queued = false, put = false, first = false; |
| |
| if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) { |
| wfo_wq = &vslow_work_queue_waits_for_occupation; |
| queue = &vslow_work_queue; |
| } else { |
| wfo_wq = &slow_work_queue_waits_for_occupation; |
| queue = &slow_work_queue; |
| } |
| |
| spin_lock_irqsave(&slow_work_queue_lock, flags); |
| if (likely(!test_bit(SLOW_WORK_CANCELLING, &work->flags))) { |
| clear_bit(SLOW_WORK_DELAYED, &work->flags); |
| |
| if (test_bit(SLOW_WORK_EXECUTING, &work->flags)) { |
| /* we discard the reference the timer was holding in |
| * favour of the one the executor holds */ |
| set_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags); |
| put = true; |
| } else { |
| slow_work_mark_time(work); |
| list_add_tail(&work->link, queue); |
| queued = true; |
| if (work->link.prev == queue) |
| first = true; |
| } |
| } |
| |
| spin_unlock_irqrestore(&slow_work_queue_lock, flags); |
| if (put) |
| slow_work_put_ref(work); |
| if (first) |
| wake_up(wfo_wq); |
| if (queued) |
| wake_up(&slow_work_thread_wq); |
| } |
| |
| /** |
| * delayed_slow_work_enqueue - Schedule a delayed slow work item for processing |
| * @dwork: The delayed work item to queue |
| * @delay: When to start executing the work, in jiffies from now |
| * |
| * This is similar to slow_work_enqueue(), but it adds a delay before the work |
| * is actually queued for processing. |
| * |
| * The item can have delayed processing requested on it whilst it is being |
| * executed. The delay will begin immediately, and if it expires before the |
| * item finishes executing, the item will be placed back on the queue when it |
| * has done executing. |
| */ |
| int delayed_slow_work_enqueue(struct delayed_slow_work *dwork, |
| unsigned long delay) |
| { |
| struct slow_work *work = &dwork->work; |
| unsigned long flags; |
| int ret; |
| |
| if (delay == 0) |
| return slow_work_enqueue(&dwork->work); |
| |
| BUG_ON(slow_work_user_count <= 0); |
| BUG_ON(!work); |
| BUG_ON(!work->ops); |
| |
| if (test_bit(SLOW_WORK_CANCELLING, &work->flags)) |
| return -ECANCELED; |
| |
| if (!test_and_set_bit_lock(SLOW_WORK_PENDING, &work->flags)) { |
| spin_lock_irqsave(&slow_work_queue_lock, flags); |
| |
| if (test_bit(SLOW_WORK_CANCELLING, &work->flags)) |
| goto cancelled; |
| |
| /* the timer holds a reference whilst it is pending */ |
| ret = slow_work_get_ref(work); |
| if (ret < 0) |
| goto cant_get_ref; |
| |
| if (test_and_set_bit(SLOW_WORK_DELAYED, &work->flags)) |
| BUG(); |
| dwork->timer.expires = jiffies + delay; |
| dwork->timer.data = (unsigned long) work; |
| dwork->timer.function = delayed_slow_work_timer; |
| add_timer(&dwork->timer); |
| |
| spin_unlock_irqrestore(&slow_work_queue_lock, flags); |
| } |
| |
| return 0; |
| |
| cancelled: |
| ret = -ECANCELED; |
| cant_get_ref: |
| spin_unlock_irqrestore(&slow_work_queue_lock, flags); |
| return ret; |
| } |
| EXPORT_SYMBOL(delayed_slow_work_enqueue); |
| |
| /* |
| * Schedule a cull of the thread pool at some time in the near future |
| */ |
| static void slow_work_schedule_cull(void) |
| { |
| mod_timer(&slow_work_cull_timer, |
| round_jiffies(jiffies + SLOW_WORK_CULL_TIMEOUT)); |
| } |
| |
| /* |
| * Worker thread culling algorithm |
| */ |
| static bool slow_work_cull_thread(void) |
| { |
| unsigned long flags; |
| bool do_cull = false; |
| |
| spin_lock_irqsave(&slow_work_queue_lock, flags); |
| |
| if (slow_work_cull) { |
| slow_work_cull = false; |
| |
| if (list_empty(&slow_work_queue) && |
| list_empty(&vslow_work_queue) && |
| atomic_read(&slow_work_thread_count) > |
| slow_work_min_threads) { |
| slow_work_schedule_cull(); |
| do_cull = true; |
| } |
| } |
| |
| spin_unlock_irqrestore(&slow_work_queue_lock, flags); |
| return do_cull; |
| } |
| |
| /* |
| * Determine if there is slow work available for dispatch |
| */ |
| static inline bool slow_work_available(int vsmax) |
| { |
| return !list_empty(&slow_work_queue) || |
| (!list_empty(&vslow_work_queue) && |
| atomic_read(&vslow_work_executing_count) < vsmax); |
| } |
| |
| /* |
| * Worker thread dispatcher |
| */ |
| static int slow_work_thread(void *_data) |
| { |
| int vsmax, id; |
| |
| DEFINE_WAIT(wait); |
| |
| set_freezable(); |
| set_user_nice(current, -5); |
| |
| /* allocate ourselves an ID */ |
| spin_lock_irq(&slow_work_queue_lock); |
| id = find_first_zero_bit(slow_work_ids, SLOW_WORK_THREAD_LIMIT); |
| BUG_ON(id < 0 || id >= SLOW_WORK_THREAD_LIMIT); |
| __set_bit(id, slow_work_ids); |
| slow_work_set_thread_pid(id, current->pid); |
| spin_unlock_irq(&slow_work_queue_lock); |
| |
| sprintf(current->comm, "kslowd%03u", id); |
| |
| for (;;) { |
| vsmax = vslow_work_proportion; |
| vsmax *= atomic_read(&slow_work_thread_count); |
| vsmax /= 100; |
| |
| prepare_to_wait_exclusive(&slow_work_thread_wq, &wait, |
| TASK_INTERRUPTIBLE); |
| if (!freezing(current) && |
| !slow_work_threads_should_exit && |
| !slow_work_available(vsmax) && |
| !slow_work_cull) |
| schedule(); |
| finish_wait(&slow_work_thread_wq, &wait); |
| |
| try_to_freeze(); |
| |
| vsmax = vslow_work_proportion; |
| vsmax *= atomic_read(&slow_work_thread_count); |
| vsmax /= 100; |
| |
| if (slow_work_available(vsmax) && slow_work_execute(id)) { |
| cond_resched(); |
| if (list_empty(&slow_work_queue) && |
| list_empty(&vslow_work_queue) && |
| atomic_read(&slow_work_thread_count) > |
| slow_work_min_threads) |
| slow_work_schedule_cull(); |
| continue; |
| } |
| |
| if (slow_work_threads_should_exit) |
| break; |
| |
| if (slow_work_cull && slow_work_cull_thread()) |
| break; |
| } |
| |
| spin_lock_irq(&slow_work_queue_lock); |
| slow_work_set_thread_pid(id, 0); |
| __clear_bit(id, slow_work_ids); |
| spin_unlock_irq(&slow_work_queue_lock); |
| |
| if (atomic_dec_and_test(&slow_work_thread_count)) |
| complete_and_exit(&slow_work_last_thread_exited, 0); |
| return 0; |
| } |
| |
| /* |
| * Handle thread cull timer expiration |
| */ |
| static void slow_work_cull_timeout(unsigned long data) |
| { |
| slow_work_cull = true; |
| wake_up(&slow_work_thread_wq); |
| } |
| |
| /* |
| * Start a new slow work thread |
| */ |
| static void slow_work_new_thread_execute(struct slow_work *work) |
| { |
| struct task_struct *p; |
| |
| if (slow_work_threads_should_exit) |
| return; |
| |
| if (atomic_read(&slow_work_thread_count) >= slow_work_max_threads) |
| return; |
| |
| if (!mutex_trylock(&slow_work_user_lock)) |
| return; |
| |
| slow_work_may_not_start_new_thread = true; |
| atomic_inc(&slow_work_thread_count); |
| p = kthread_run(slow_work_thread, NULL, "kslowd"); |
| if (IS_ERR(p)) { |
| printk(KERN_DEBUG "Slow work thread pool: OOM\n"); |
| if (atomic_dec_and_test(&slow_work_thread_count)) |
| BUG(); /* we're running on a slow work thread... */ |
| mod_timer(&slow_work_oom_timer, |
| round_jiffies(jiffies + SLOW_WORK_OOM_TIMEOUT)); |
| } else { |
| /* ratelimit the starting of new threads */ |
| mod_timer(&slow_work_oom_timer, jiffies + 1); |
| } |
| |
| mutex_unlock(&slow_work_user_lock); |
| } |
| |
| static const struct slow_work_ops slow_work_new_thread_ops = { |
| .owner = THIS_MODULE, |
| .execute = slow_work_new_thread_execute, |
| #ifdef CONFIG_SLOW_WORK_DEBUG |
| .desc = slow_work_new_thread_desc, |
| #endif |
| }; |
| |
| /* |
| * post-OOM new thread start suppression expiration |
| */ |
| static void slow_work_oom_timeout(unsigned long data) |
| { |
| slow_work_may_not_start_new_thread = false; |
| } |
| |
| #ifdef CONFIG_SYSCTL |
| /* |
| * Handle adjustment of the minimum number of threads |
| */ |
| static int slow_work_min_threads_sysctl(struct ctl_table *table, int write, |
| void __user *buffer, |
| size_t *lenp, loff_t *ppos) |
| { |
| int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
| int n; |
| |
| if (ret == 0) { |
| mutex_lock(&slow_work_user_lock); |
| if (slow_work_user_count > 0) { |
| /* see if we need to start or stop threads */ |
| n = atomic_read(&slow_work_thread_count) - |
| slow_work_min_threads; |
| |
| if (n < 0 && !slow_work_may_not_start_new_thread) |
| slow_work_enqueue(&slow_work_new_thread); |
| else if (n > 0) |
| slow_work_schedule_cull(); |
| } |
| mutex_unlock(&slow_work_user_lock); |
| } |
| |
| return ret; |
| } |
| |
| /* |
| * Handle adjustment of the maximum number of threads |
| */ |
| static int slow_work_max_threads_sysctl(struct ctl_table *table, int write, |
| void __user *buffer, |
| size_t *lenp, loff_t *ppos) |
| { |
| int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
| int n; |
| |
| if (ret == 0) { |
| mutex_lock(&slow_work_user_lock); |
| if (slow_work_user_count > 0) { |
| /* see if we need to stop threads */ |
| n = slow_work_max_threads - |
| atomic_read(&slow_work_thread_count); |
| |
| if (n < 0) |
| slow_work_schedule_cull(); |
| } |
| mutex_unlock(&slow_work_user_lock); |
| } |
| |
| return ret; |
| } |
| #endif /* CONFIG_SYSCTL */ |
| |
| /** |
| * slow_work_register_user - Register a user of the facility |
| * @module: The module about to make use of the facility |
| * |
| * Register a user of the facility, starting up the initial threads if there |
| * aren't any other users at this point. This will return 0 if successful, or |
| * an error if not. |
| */ |
| int slow_work_register_user(struct module *module) |
| { |
| struct task_struct *p; |
| int loop; |
| |
| mutex_lock(&slow_work_user_lock); |
| |
| if (slow_work_user_count == 0) { |
| printk(KERN_NOTICE "Slow work thread pool: Starting up\n"); |
| init_completion(&slow_work_last_thread_exited); |
| |
| slow_work_threads_should_exit = false; |
| slow_work_init(&slow_work_new_thread, |
| &slow_work_new_thread_ops); |
| slow_work_may_not_start_new_thread = false; |
| slow_work_cull = false; |
| |
| /* start the minimum number of threads */ |
| for (loop = 0; loop < slow_work_min_threads; loop++) { |
| atomic_inc(&slow_work_thread_count); |
| p = kthread_run(slow_work_thread, NULL, "kslowd"); |
| if (IS_ERR(p)) |
| goto error; |
| } |
| printk(KERN_NOTICE "Slow work thread pool: Ready\n"); |
| } |
| |
| slow_work_user_count++; |
| mutex_unlock(&slow_work_user_lock); |
| return 0; |
| |
| error: |
| if (atomic_dec_and_test(&slow_work_thread_count)) |
| complete(&slow_work_last_thread_exited); |
| if (loop > 0) { |
| printk(KERN_ERR "Slow work thread pool:" |
| " Aborting startup on ENOMEM\n"); |
| slow_work_threads_should_exit = true; |
| wake_up_all(&slow_work_thread_wq); |
| wait_for_completion(&slow_work_last_thread_exited); |
| printk(KERN_ERR "Slow work thread pool: Aborted\n"); |
| } |
| mutex_unlock(&slow_work_user_lock); |
| return PTR_ERR(p); |
| } |
| EXPORT_SYMBOL(slow_work_register_user); |
| |
| /* |
| * wait for all outstanding items from the calling module to complete |
| * - note that more items may be queued whilst we're waiting |
| */ |
| static void slow_work_wait_for_items(struct module *module) |
| { |
| #ifdef CONFIG_MODULES |
| DECLARE_WAITQUEUE(myself, current); |
| struct slow_work *work; |
| int loop; |
| |
| mutex_lock(&slow_work_unreg_sync_lock); |
| add_wait_queue(&slow_work_unreg_wq, &myself); |
| |
| for (;;) { |
| spin_lock_irq(&slow_work_queue_lock); |
| |
| /* first of all, we wait for the last queued item in each list |
| * to be processed */ |
| list_for_each_entry_reverse(work, &vslow_work_queue, link) { |
| if (work->owner == module) { |
| set_current_state(TASK_UNINTERRUPTIBLE); |
| slow_work_unreg_work_item = work; |
| goto do_wait; |
| } |
| } |
| list_for_each_entry_reverse(work, &slow_work_queue, link) { |
| if (work->owner == module) { |
| set_current_state(TASK_UNINTERRUPTIBLE); |
| slow_work_unreg_work_item = work; |
| goto do_wait; |
| } |
| } |
| |
| /* then we wait for the items being processed to finish */ |
| slow_work_unreg_module = module; |
| smp_mb(); |
| for (loop = 0; loop < SLOW_WORK_THREAD_LIMIT; loop++) { |
| if (slow_work_thread_processing[loop] == module) |
| goto do_wait; |
| } |
| spin_unlock_irq(&slow_work_queue_lock); |
| break; /* okay, we're done */ |
| |
| do_wait: |
| spin_unlock_irq(&slow_work_queue_lock); |
| schedule(); |
| slow_work_unreg_work_item = NULL; |
| slow_work_unreg_module = NULL; |
| } |
| |
| remove_wait_queue(&slow_work_unreg_wq, &myself); |
| mutex_unlock(&slow_work_unreg_sync_lock); |
| #endif /* CONFIG_MODULES */ |
| } |
| |
| /** |
| * slow_work_unregister_user - Unregister a user of the facility |
| * @module: The module whose items should be cleared |
| * |
| * Unregister a user of the facility, killing all the threads if this was the |
| * last one. |
| * |
| * This waits for all the work items belonging to the nominated module to go |
| * away before proceeding. |
| */ |
| void slow_work_unregister_user(struct module *module) |
| { |
| /* first of all, wait for all outstanding items from the calling module |
| * to complete */ |
| if (module) |
| slow_work_wait_for_items(module); |
| |
| /* then we can actually go about shutting down the facility if need |
| * be */ |
| mutex_lock(&slow_work_user_lock); |
| |
| BUG_ON(slow_work_user_count <= 0); |
| |
| slow_work_user_count--; |
| if (slow_work_user_count == 0) { |
| printk(KERN_NOTICE "Slow work thread pool: Shutting down\n"); |
| slow_work_threads_should_exit = true; |
| del_timer_sync(&slow_work_cull_timer); |
| del_timer_sync(&slow_work_oom_timer); |
| wake_up_all(&slow_work_thread_wq); |
| wait_for_completion(&slow_work_last_thread_exited); |
| printk(KERN_NOTICE "Slow work thread pool:" |
| " Shut down complete\n"); |
| } |
| |
| mutex_unlock(&slow_work_user_lock); |
| } |
| EXPORT_SYMBOL(slow_work_unregister_user); |
| |
| /* |
| * Initialise the slow work facility |
| */ |
| static int __init init_slow_work(void) |
| { |
| unsigned nr_cpus = num_possible_cpus(); |
| |
| if (slow_work_max_threads < nr_cpus) |
| slow_work_max_threads = nr_cpus; |
| #ifdef CONFIG_SYSCTL |
| if (slow_work_max_max_threads < nr_cpus * 2) |
| slow_work_max_max_threads = nr_cpus * 2; |
| #endif |
| #ifdef CONFIG_SLOW_WORK_DEBUG |
| { |
| struct dentry *dbdir; |
| |
| dbdir = debugfs_create_dir("slow_work", NULL); |
| if (dbdir && !IS_ERR(dbdir)) |
| debugfs_create_file("runqueue", S_IFREG | 0400, dbdir, |
| NULL, &slow_work_runqueue_fops); |
| } |
| #endif |
| return 0; |
| } |
| |
| subsys_initcall(init_slow_work); |