/* 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> #define SLOW_WORK_CULL_TIMEOUT (5 * HZ) /* cull threads 5s after running out of * things to do */#define SLOW_WORK_OOM_TIMEOUT (5 * HZ) /* can't start new threads for 5s after * OOM */ static void slow_work_cull_timeout(unsigned long);static void slow_work_oom_timeout(unsigned long); #ifdef CONFIG_SYSCTLstatic int slow_work_min_threads_sysctl(struct ctl_table *, int, struct file *, void __user *, size_t *, loff_t *); static int slow_work_max_threads_sysctl(struct ctl_table *, int , struct file *, 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_SYSCTLstatic const int slow_work_min_min_threads = 2;static int slow_work_max_max_threads = 255;static const int slow_work_min_vslow = 1;static const int slow_work_max_vslow = 99; ctl_table slow_work_sysctls[] = { { .ctl_name = CTL_UNNUMBERED, .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, }, { .ctl_name = CTL_UNNUMBERED, .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, }, { .ctl_name = CTL_UNNUMBERED, .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, }, { .ctl_name = 0 }};#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 */ /* * 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. */static LIST_HEAD(slow_work_queue);static LIST_HEAD(vslow_work_queue);static DEFINE_SPINLOCK(slow_work_queue_lock); /* * 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); /* * 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 bool slow_work_execute(void){ 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 */ } spin_unlock_irq(&slow_work_queue_lock); if (!work) return false; if (!test_and_clear_bit(SLOW_WORK_PENDING, &work->flags)) BUG(); work->ops->execute(work); if (very_slow) atomic_dec(&vslow_work_executing_count); clear_bit_unlock(SLOW_WORK_EXECUTING, &work->flags); /* 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); } work->ops->put_ref(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 */ 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); return true;} /** * 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. */int slow_work_enqueue(struct slow_work *work){ unsigned long flags; BUG_ON(slow_work_user_count <= 0); BUG_ON(!work); BUG_ON(!work->ops); BUG_ON(!work->ops->get_ref); /* 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)) { spin_lock_irqsave(&slow_work_queue_lock, flags); /* 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 { if (work->ops->get_ref(work) < 0) goto cant_get_ref; 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); wake_up(&slow_work_thread_wq); } spin_unlock_irqrestore(&slow_work_queue_lock, flags); } return 0; cant_get_ref: spin_unlock_irqrestore(&slow_work_queue_lock, flags); return -EAGAIN;}EXPORT_SYMBOL(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; DEFINE_WAIT(wait); set_freezable(); set_user_nice(current, -5); 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()) { 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; } 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);} /* * Get a reference on slow work thread starter */static int slow_work_new_thread_get_ref(struct slow_work *work){ return 0;} /* * Drop a reference on slow work thread starter */static void slow_work_new_thread_put_ref(struct slow_work *work){} /* * 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 = { .get_ref = slow_work_new_thread_get_ref, .put_ref = slow_work_new_thread_put_ref, .execute = slow_work_new_thread_execute,}; /* * 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, struct file *filp, void __user *buffer, size_t *lenp, loff_t *ppos){ int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos); int n;Lines 1–500 of 645. 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/* 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> #define SLOW_WORK_CULL_TIMEOUT (5 * HZ) /* cull threads 5s after running out of * things to do */ #define SLOW_WORK_OOM_TIMEOUT (5 * HZ) /* can't start new threads for 5s after * OOM */ 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, struct file *, void __user *, size_t *, loff_t *); static int slow_work_max_threads_sysctl(struct ctl_table *, int , struct file *, 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 = 255; static const int slow_work_min_vslow = 1; static const int slow_work_max_vslow = 99; ctl_table slow_work_sysctls[] = { { .ctl_name = CTL_UNNUMBERED, .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, }, { .ctl_name = CTL_UNNUMBERED, .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, }, { .ctl_name = CTL_UNNUMBERED, .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, }, { .ctl_name = 0 } }; #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 */ /* * 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. */ static LIST_HEAD(slow_work_queue); static LIST_HEAD(vslow_work_queue); static DEFINE_SPINLOCK(slow_work_queue_lock); /* * 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); /* * 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 bool slow_work_execute(void) { 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 */ } spin_unlock_irq(&slow_work_queue_lock); if (!work) return false; if (!test_and_clear_bit(SLOW_WORK_PENDING, &work->flags)) BUG(); work->ops->execute(work); if (very_slow) atomic_dec(&vslow_work_executing_count); clear_bit_unlock(SLOW_WORK_EXECUTING, &work->flags); /* 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); } work->ops->put_ref(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 */ 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); return true; } /** * 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. */ int slow_work_enqueue(struct slow_work *work) { unsigned long flags; BUG_ON(slow_work_user_count <= 0); BUG_ON(!work); BUG_ON(!work->ops); BUG_ON(!work->ops->get_ref); /* 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)) { spin_lock_irqsave(&slow_work_queue_lock, flags); /* 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 { if (work->ops->get_ref(work) < 0) goto cant_get_ref; 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); wake_up(&slow_work_thread_wq); } spin_unlock_irqrestore(&slow_work_queue_lock, flags); } return 0; cant_get_ref: spin_unlock_irqrestore(&slow_work_queue_lock, flags); return -EAGAIN; } EXPORT_SYMBOL(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; DEFINE_WAIT(wait); set_freezable(); set_user_nice(current, -5); 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()) { 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; } 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); } /* * Get a reference on slow work thread starter */ static int slow_work_new_thread_get_ref(struct slow_work *work) { return 0; } /* * Drop a reference on slow work thread starter */ static void slow_work_new_thread_put_ref(struct slow_work *work) { } /* * 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 = { .get_ref = slow_work_new_thread_get_ref, .put_ref = slow_work_new_thread_put_ref, .execute = slow_work_new_thread_execute, }; /* * 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, struct file *filp, void __user *buffer, size_t *lenp, loff_t *ppos) { int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos); int n;