diff options
Diffstat (limited to 'kernel/slow-work.c')
| -rw-r--r-- | kernel/slow-work.c | 1068 |
1 files changed, 0 insertions, 1068 deletions
diff --git a/kernel/slow-work.c b/kernel/slow-work.c deleted file mode 100644 index 7d3f4fa9ef4f..000000000000 --- a/kernel/slow-work.c +++ /dev/null @@ -1,1068 +0,0 @@ -/* 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); |