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Diffstat (limited to 'module/spl/spl-taskq.c')
| -rw-r--r-- | module/spl/spl-taskq.c | 1305 |
1 files changed, 1305 insertions, 0 deletions
diff --git a/module/spl/spl-taskq.c b/module/spl/spl-taskq.c new file mode 100644 index 000000000..2919a942a --- /dev/null +++ b/module/spl/spl-taskq.c @@ -0,0 +1,1305 @@ +/* + * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC. + * Copyright (C) 2007 The Regents of the University of California. + * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER). + * Written by Brian Behlendorf <[email protected]>. + * UCRL-CODE-235197 + * + * This file is part of the SPL, Solaris Porting Layer. + * For details, see <http://zfsonlinux.org/>. + * + * The SPL is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2 of the License, or (at your + * option) any later version. + * + * The SPL is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * for more details. + * + * You should have received a copy of the GNU General Public License along + * with the SPL. If not, see <http://www.gnu.org/licenses/>. + * + * Solaris Porting Layer (SPL) Task Queue Implementation. + */ + +#include <sys/taskq.h> +#include <sys/kmem.h> +#include <sys/tsd.h> + +int spl_taskq_thread_bind = 0; +module_param(spl_taskq_thread_bind, int, 0644); +MODULE_PARM_DESC(spl_taskq_thread_bind, "Bind taskq thread to CPU by default"); + + +int spl_taskq_thread_dynamic = 1; +module_param(spl_taskq_thread_dynamic, int, 0644); +MODULE_PARM_DESC(spl_taskq_thread_dynamic, "Allow dynamic taskq threads"); + +int spl_taskq_thread_priority = 1; +module_param(spl_taskq_thread_priority, int, 0644); +MODULE_PARM_DESC(spl_taskq_thread_priority, + "Allow non-default priority for taskq threads"); + +int spl_taskq_thread_sequential = 4; +module_param(spl_taskq_thread_sequential, int, 0644); +MODULE_PARM_DESC(spl_taskq_thread_sequential, + "Create new taskq threads after N sequential tasks"); + +/* Global system-wide dynamic task queue available for all consumers */ +taskq_t *system_taskq; +EXPORT_SYMBOL(system_taskq); +/* Global dynamic task queue for long delay */ +taskq_t *system_delay_taskq; +EXPORT_SYMBOL(system_delay_taskq); + +/* Private dedicated taskq for creating new taskq threads on demand. */ +static taskq_t *dynamic_taskq; +static taskq_thread_t *taskq_thread_create(taskq_t *); + +/* List of all taskqs */ +LIST_HEAD(tq_list); +DECLARE_RWSEM(tq_list_sem); +static uint_t taskq_tsd; + +static int +task_km_flags(uint_t flags) +{ + if (flags & TQ_NOSLEEP) + return (KM_NOSLEEP); + + if (flags & TQ_PUSHPAGE) + return (KM_PUSHPAGE); + + return (KM_SLEEP); +} + +/* + * taskq_find_by_name - Find the largest instance number of a named taskq. + */ +static int +taskq_find_by_name(const char *name) +{ + struct list_head *tql; + taskq_t *tq; + + list_for_each_prev(tql, &tq_list) { + tq = list_entry(tql, taskq_t, tq_taskqs); + if (strcmp(name, tq->tq_name) == 0) + return (tq->tq_instance); + } + return (-1); +} + +/* + * NOTE: Must be called with tq->tq_lock held, returns a list_t which + * is not attached to the free, work, or pending taskq lists. + */ +static taskq_ent_t * +task_alloc(taskq_t *tq, uint_t flags, unsigned long *irqflags) +{ + taskq_ent_t *t; + int count = 0; + + ASSERT(tq); +retry: + /* Acquire taskq_ent_t's from free list if available */ + if (!list_empty(&tq->tq_free_list) && !(flags & TQ_NEW)) { + t = list_entry(tq->tq_free_list.next, taskq_ent_t, tqent_list); + + ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC)); + ASSERT(!(t->tqent_flags & TQENT_FLAG_CANCEL)); + ASSERT(!timer_pending(&t->tqent_timer)); + + list_del_init(&t->tqent_list); + return (t); + } + + /* Free list is empty and memory allocations are prohibited */ + if (flags & TQ_NOALLOC) + return (NULL); + + /* Hit maximum taskq_ent_t pool size */ + if (tq->tq_nalloc >= tq->tq_maxalloc) { + if (flags & TQ_NOSLEEP) + return (NULL); + + /* + * Sleep periodically polling the free list for an available + * taskq_ent_t. Dispatching with TQ_SLEEP should always succeed + * but we cannot block forever waiting for an taskq_ent_t to + * show up in the free list, otherwise a deadlock can happen. + * + * Therefore, we need to allocate a new task even if the number + * of allocated tasks is above tq->tq_maxalloc, but we still + * end up delaying the task allocation by one second, thereby + * throttling the task dispatch rate. + */ + spin_unlock_irqrestore(&tq->tq_lock, *irqflags); + schedule_timeout(HZ / 100); + spin_lock_irqsave_nested(&tq->tq_lock, *irqflags, + tq->tq_lock_class); + if (count < 100) { + count++; + goto retry; + } + } + + spin_unlock_irqrestore(&tq->tq_lock, *irqflags); + t = kmem_alloc(sizeof (taskq_ent_t), task_km_flags(flags)); + spin_lock_irqsave_nested(&tq->tq_lock, *irqflags, tq->tq_lock_class); + + if (t) { + taskq_init_ent(t); + tq->tq_nalloc++; + } + + return (t); +} + +/* + * NOTE: Must be called with tq->tq_lock held, expects the taskq_ent_t + * to already be removed from the free, work, or pending taskq lists. + */ +static void +task_free(taskq_t *tq, taskq_ent_t *t) +{ + ASSERT(tq); + ASSERT(t); + ASSERT(list_empty(&t->tqent_list)); + ASSERT(!timer_pending(&t->tqent_timer)); + + kmem_free(t, sizeof (taskq_ent_t)); + tq->tq_nalloc--; +} + +/* + * NOTE: Must be called with tq->tq_lock held, either destroys the + * taskq_ent_t if too many exist or moves it to the free list for later use. + */ +static void +task_done(taskq_t *tq, taskq_ent_t *t) +{ + ASSERT(tq); + ASSERT(t); + + /* Wake tasks blocked in taskq_wait_id() */ + wake_up_all(&t->tqent_waitq); + + list_del_init(&t->tqent_list); + + if (tq->tq_nalloc <= tq->tq_minalloc) { + t->tqent_id = TASKQID_INVALID; + t->tqent_func = NULL; + t->tqent_arg = NULL; + t->tqent_flags = 0; + + list_add_tail(&t->tqent_list, &tq->tq_free_list); + } else { + task_free(tq, t); + } +} + +/* + * When a delayed task timer expires remove it from the delay list and + * add it to the priority list in order for immediate processing. + */ +static void +task_expire_impl(taskq_ent_t *t) +{ + taskq_ent_t *w; + taskq_t *tq = t->tqent_taskq; + struct list_head *l; + unsigned long flags; + + spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class); + + if (t->tqent_flags & TQENT_FLAG_CANCEL) { + ASSERT(list_empty(&t->tqent_list)); + spin_unlock_irqrestore(&tq->tq_lock, flags); + return; + } + + t->tqent_birth = jiffies; + /* + * The priority list must be maintained in strict task id order + * from lowest to highest for lowest_id to be easily calculable. + */ + list_del(&t->tqent_list); + list_for_each_prev(l, &tq->tq_prio_list) { + w = list_entry(l, taskq_ent_t, tqent_list); + if (w->tqent_id < t->tqent_id) { + list_add(&t->tqent_list, l); + break; + } + } + if (l == &tq->tq_prio_list) + list_add(&t->tqent_list, &tq->tq_prio_list); + + spin_unlock_irqrestore(&tq->tq_lock, flags); + + wake_up(&tq->tq_work_waitq); +} + +#ifdef HAVE_KERNEL_TIMER_FUNCTION_TIMER_LIST +static void +task_expire(struct timer_list *tl) +{ + taskq_ent_t *t = from_timer(t, tl, tqent_timer); + task_expire_impl(t); +} +#else +static void +task_expire(unsigned long data) +{ + task_expire_impl((taskq_ent_t *)data); +} +#endif + +/* + * Returns the lowest incomplete taskqid_t. The taskqid_t may + * be queued on the pending list, on the priority list, on the + * delay list, or on the work list currently being handled, but + * it is not 100% complete yet. + */ +static taskqid_t +taskq_lowest_id(taskq_t *tq) +{ + taskqid_t lowest_id = tq->tq_next_id; + taskq_ent_t *t; + taskq_thread_t *tqt; + + ASSERT(tq); + + if (!list_empty(&tq->tq_pend_list)) { + t = list_entry(tq->tq_pend_list.next, taskq_ent_t, tqent_list); + lowest_id = MIN(lowest_id, t->tqent_id); + } + + if (!list_empty(&tq->tq_prio_list)) { + t = list_entry(tq->tq_prio_list.next, taskq_ent_t, tqent_list); + lowest_id = MIN(lowest_id, t->tqent_id); + } + + if (!list_empty(&tq->tq_delay_list)) { + t = list_entry(tq->tq_delay_list.next, taskq_ent_t, tqent_list); + lowest_id = MIN(lowest_id, t->tqent_id); + } + + if (!list_empty(&tq->tq_active_list)) { + tqt = list_entry(tq->tq_active_list.next, taskq_thread_t, + tqt_active_list); + ASSERT(tqt->tqt_id != TASKQID_INVALID); + lowest_id = MIN(lowest_id, tqt->tqt_id); + } + + return (lowest_id); +} + +/* + * Insert a task into a list keeping the list sorted by increasing taskqid. + */ +static void +taskq_insert_in_order(taskq_t *tq, taskq_thread_t *tqt) +{ + taskq_thread_t *w; + struct list_head *l; + + ASSERT(tq); + ASSERT(tqt); + + list_for_each_prev(l, &tq->tq_active_list) { + w = list_entry(l, taskq_thread_t, tqt_active_list); + if (w->tqt_id < tqt->tqt_id) { + list_add(&tqt->tqt_active_list, l); + break; + } + } + if (l == &tq->tq_active_list) + list_add(&tqt->tqt_active_list, &tq->tq_active_list); +} + +/* + * Find and return a task from the given list if it exists. The list + * must be in lowest to highest task id order. + */ +static taskq_ent_t * +taskq_find_list(taskq_t *tq, struct list_head *lh, taskqid_t id) +{ + struct list_head *l; + taskq_ent_t *t; + + list_for_each(l, lh) { + t = list_entry(l, taskq_ent_t, tqent_list); + + if (t->tqent_id == id) + return (t); + + if (t->tqent_id > id) + break; + } + + return (NULL); +} + +/* + * Find an already dispatched task given the task id regardless of what + * state it is in. If a task is still pending it will be returned. + * If a task is executing, then -EBUSY will be returned instead. + * If the task has already been run then NULL is returned. + */ +static taskq_ent_t * +taskq_find(taskq_t *tq, taskqid_t id) +{ + taskq_thread_t *tqt; + struct list_head *l; + taskq_ent_t *t; + + t = taskq_find_list(tq, &tq->tq_delay_list, id); + if (t) + return (t); + + t = taskq_find_list(tq, &tq->tq_prio_list, id); + if (t) + return (t); + + t = taskq_find_list(tq, &tq->tq_pend_list, id); + if (t) + return (t); + + list_for_each(l, &tq->tq_active_list) { + tqt = list_entry(l, taskq_thread_t, tqt_active_list); + if (tqt->tqt_id == id) { + /* + * Instead of returning tqt_task, we just return a non + * NULL value to prevent misuse, since tqt_task only + * has two valid fields. + */ + return (ERR_PTR(-EBUSY)); + } + } + + return (NULL); +} + +/* + * Theory for the taskq_wait_id(), taskq_wait_outstanding(), and + * taskq_wait() functions below. + * + * Taskq waiting is accomplished by tracking the lowest outstanding task + * id and the next available task id. As tasks are dispatched they are + * added to the tail of the pending, priority, or delay lists. As worker + * threads become available the tasks are removed from the heads of these + * lists and linked to the worker threads. This ensures the lists are + * kept sorted by lowest to highest task id. + * + * Therefore the lowest outstanding task id can be quickly determined by + * checking the head item from all of these lists. This value is stored + * with the taskq as the lowest id. It only needs to be recalculated when + * either the task with the current lowest id completes or is canceled. + * + * By blocking until the lowest task id exceeds the passed task id the + * taskq_wait_outstanding() function can be easily implemented. Similarly, + * by blocking until the lowest task id matches the next task id taskq_wait() + * can be implemented. + * + * Callers should be aware that when there are multiple worked threads it + * is possible for larger task ids to complete before smaller ones. Also + * when the taskq contains delay tasks with small task ids callers may + * block for a considerable length of time waiting for them to expire and + * execute. + */ +static int +taskq_wait_id_check(taskq_t *tq, taskqid_t id) +{ + int rc; + unsigned long flags; + + spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class); + rc = (taskq_find(tq, id) == NULL); + spin_unlock_irqrestore(&tq->tq_lock, flags); + + return (rc); +} + +/* + * The taskq_wait_id() function blocks until the passed task id completes. + * This does not guarantee that all lower task ids have completed. + */ +void +taskq_wait_id(taskq_t *tq, taskqid_t id) +{ + wait_event(tq->tq_wait_waitq, taskq_wait_id_check(tq, id)); +} +EXPORT_SYMBOL(taskq_wait_id); + +static int +taskq_wait_outstanding_check(taskq_t *tq, taskqid_t id) +{ + int rc; + unsigned long flags; + + spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class); + rc = (id < tq->tq_lowest_id); + spin_unlock_irqrestore(&tq->tq_lock, flags); + + return (rc); +} + +/* + * The taskq_wait_outstanding() function will block until all tasks with a + * lower taskqid than the passed 'id' have been completed. Note that all + * task id's are assigned monotonically at dispatch time. Zero may be + * passed for the id to indicate all tasks dispatch up to this point, + * but not after, should be waited for. + */ +void +taskq_wait_outstanding(taskq_t *tq, taskqid_t id) +{ + id = id ? id : tq->tq_next_id - 1; + wait_event(tq->tq_wait_waitq, taskq_wait_outstanding_check(tq, id)); +} +EXPORT_SYMBOL(taskq_wait_outstanding); + +static int +taskq_wait_check(taskq_t *tq) +{ + int rc; + unsigned long flags; + + spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class); + rc = (tq->tq_lowest_id == tq->tq_next_id); + spin_unlock_irqrestore(&tq->tq_lock, flags); + + return (rc); +} + +/* + * The taskq_wait() function will block until the taskq is empty. + * This means that if a taskq re-dispatches work to itself taskq_wait() + * callers will block indefinitely. + */ +void +taskq_wait(taskq_t *tq) +{ + wait_event(tq->tq_wait_waitq, taskq_wait_check(tq)); +} +EXPORT_SYMBOL(taskq_wait); + +int +taskq_member(taskq_t *tq, kthread_t *t) +{ + return (tq == (taskq_t *)tsd_get_by_thread(taskq_tsd, t)); +} +EXPORT_SYMBOL(taskq_member); + +/* + * Cancel an already dispatched task given the task id. Still pending tasks + * will be immediately canceled, and if the task is active the function will + * block until it completes. Preallocated tasks which are canceled must be + * freed by the caller. + */ +int +taskq_cancel_id(taskq_t *tq, taskqid_t id) +{ + taskq_ent_t *t; + int rc = ENOENT; + unsigned long flags; + + ASSERT(tq); + + spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class); + t = taskq_find(tq, id); + if (t && t != ERR_PTR(-EBUSY)) { + list_del_init(&t->tqent_list); + t->tqent_flags |= TQENT_FLAG_CANCEL; + + /* + * When canceling the lowest outstanding task id we + * must recalculate the new lowest outstanding id. + */ + if (tq->tq_lowest_id == t->tqent_id) { + tq->tq_lowest_id = taskq_lowest_id(tq); + ASSERT3S(tq->tq_lowest_id, >, t->tqent_id); + } + + /* + * The task_expire() function takes the tq->tq_lock so drop + * drop the lock before synchronously cancelling the timer. + */ + if (timer_pending(&t->tqent_timer)) { + spin_unlock_irqrestore(&tq->tq_lock, flags); + del_timer_sync(&t->tqent_timer); + spin_lock_irqsave_nested(&tq->tq_lock, flags, + tq->tq_lock_class); + } + + if (!(t->tqent_flags & TQENT_FLAG_PREALLOC)) + task_done(tq, t); + + rc = 0; + } + spin_unlock_irqrestore(&tq->tq_lock, flags); + + if (t == ERR_PTR(-EBUSY)) { + taskq_wait_id(tq, id); + rc = EBUSY; + } + + return (rc); +} +EXPORT_SYMBOL(taskq_cancel_id); + +static int taskq_thread_spawn(taskq_t *tq); + +taskqid_t +taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags) +{ + taskq_ent_t *t; + taskqid_t rc = TASKQID_INVALID; + unsigned long irqflags; + + ASSERT(tq); + ASSERT(func); + + spin_lock_irqsave_nested(&tq->tq_lock, irqflags, tq->tq_lock_class); + + /* Taskq being destroyed and all tasks drained */ + if (!(tq->tq_flags & TASKQ_ACTIVE)) + goto out; + + /* Do not queue the task unless there is idle thread for it */ + ASSERT(tq->tq_nactive <= tq->tq_nthreads); + if ((flags & TQ_NOQUEUE) && (tq->tq_nactive == tq->tq_nthreads)) { + /* Dynamic taskq may be able to spawn another thread */ + if (!(tq->tq_flags & TASKQ_DYNAMIC) || + taskq_thread_spawn(tq) == 0) + goto out; + } + + if ((t = task_alloc(tq, flags, &irqflags)) == NULL) + goto out; + + spin_lock(&t->tqent_lock); + + /* Queue to the front of the list to enforce TQ_NOQUEUE semantics */ + if (flags & TQ_NOQUEUE) + list_add(&t->tqent_list, &tq->tq_prio_list); + /* Queue to the priority list instead of the pending list */ + else if (flags & TQ_FRONT) + list_add_tail(&t->tqent_list, &tq->tq_prio_list); + else + list_add_tail(&t->tqent_list, &tq->tq_pend_list); + + t->tqent_id = rc = tq->tq_next_id; + tq->tq_next_id++; + t->tqent_func = func; + t->tqent_arg = arg; + t->tqent_taskq = tq; +#ifndef HAVE_KERNEL_TIMER_FUNCTION_TIMER_LIST + t->tqent_timer.data = 0; +#endif + t->tqent_timer.function = NULL; + t->tqent_timer.expires = 0; + t->tqent_birth = jiffies; + + ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC)); + + spin_unlock(&t->tqent_lock); + + wake_up(&tq->tq_work_waitq); +out: + /* Spawn additional taskq threads if required. */ + if (!(flags & TQ_NOQUEUE) && tq->tq_nactive == tq->tq_nthreads) + (void) taskq_thread_spawn(tq); + + spin_unlock_irqrestore(&tq->tq_lock, irqflags); + return (rc); +} +EXPORT_SYMBOL(taskq_dispatch); + +taskqid_t +taskq_dispatch_delay(taskq_t *tq, task_func_t func, void *arg, + uint_t flags, clock_t expire_time) +{ + taskqid_t rc = TASKQID_INVALID; + taskq_ent_t *t; + unsigned long irqflags; + + ASSERT(tq); + ASSERT(func); + + spin_lock_irqsave_nested(&tq->tq_lock, irqflags, tq->tq_lock_class); + + /* Taskq being destroyed and all tasks drained */ + if (!(tq->tq_flags & TASKQ_ACTIVE)) + goto out; + + if ((t = task_alloc(tq, flags, &irqflags)) == NULL) + goto out; + + spin_lock(&t->tqent_lock); + + /* Queue to the delay list for subsequent execution */ + list_add_tail(&t->tqent_list, &tq->tq_delay_list); + + t->tqent_id = rc = tq->tq_next_id; + tq->tq_next_id++; + t->tqent_func = func; + t->tqent_arg = arg; + t->tqent_taskq = tq; +#ifndef HAVE_KERNEL_TIMER_FUNCTION_TIMER_LIST + t->tqent_timer.data = (unsigned long)t; +#endif + t->tqent_timer.function = task_expire; + t->tqent_timer.expires = (unsigned long)expire_time; + add_timer(&t->tqent_timer); + + ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC)); + + spin_unlock(&t->tqent_lock); +out: + /* Spawn additional taskq threads if required. */ + if (tq->tq_nactive == tq->tq_nthreads) + (void) taskq_thread_spawn(tq); + spin_unlock_irqrestore(&tq->tq_lock, irqflags); + return (rc); +} +EXPORT_SYMBOL(taskq_dispatch_delay); + +void +taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags, + taskq_ent_t *t) +{ + unsigned long irqflags; + ASSERT(tq); + ASSERT(func); + + spin_lock_irqsave_nested(&tq->tq_lock, irqflags, + tq->tq_lock_class); + + /* Taskq being destroyed and all tasks drained */ + if (!(tq->tq_flags & TASKQ_ACTIVE)) { + t->tqent_id = TASKQID_INVALID; + goto out; + } + + if ((flags & TQ_NOQUEUE) && (tq->tq_nactive == tq->tq_nthreads)) { + /* Dynamic taskq may be able to spawn another thread */ + if (!(tq->tq_flags & TASKQ_DYNAMIC) || + taskq_thread_spawn(tq) == 0) + goto out2; + flags |= TQ_FRONT; + } + + spin_lock(&t->tqent_lock); + + /* + * Make sure the entry is not on some other taskq; it is important to + * ASSERT() under lock + */ + ASSERT(taskq_empty_ent(t)); + + /* + * Mark it as a prealloc'd task. This is important + * to ensure that we don't free it later. + */ + t->tqent_flags |= TQENT_FLAG_PREALLOC; + + /* Queue to the priority list instead of the pending list */ + if (flags & TQ_FRONT) + list_add_tail(&t->tqent_list, &tq->tq_prio_list); + else + list_add_tail(&t->tqent_list, &tq->tq_pend_list); + + t->tqent_id = tq->tq_next_id; + tq->tq_next_id++; + t->tqent_func = func; + t->tqent_arg = arg; + t->tqent_taskq = tq; + t->tqent_birth = jiffies; + + spin_unlock(&t->tqent_lock); + + wake_up(&tq->tq_work_waitq); +out: + /* Spawn additional taskq threads if required. */ + if (tq->tq_nactive == tq->tq_nthreads) + (void) taskq_thread_spawn(tq); +out2: + spin_unlock_irqrestore(&tq->tq_lock, irqflags); +} +EXPORT_SYMBOL(taskq_dispatch_ent); + +int +taskq_empty_ent(taskq_ent_t *t) +{ + return (list_empty(&t->tqent_list)); +} +EXPORT_SYMBOL(taskq_empty_ent); + +void +taskq_init_ent(taskq_ent_t *t) +{ + spin_lock_init(&t->tqent_lock); + init_waitqueue_head(&t->tqent_waitq); +#ifdef HAVE_KERNEL_TIMER_FUNCTION_TIMER_LIST + timer_setup(&t->tqent_timer, NULL, 0); +#else + init_timer(&t->tqent_timer); +#endif + INIT_LIST_HEAD(&t->tqent_list); + t->tqent_id = 0; + t->tqent_func = NULL; + t->tqent_arg = NULL; + t->tqent_flags = 0; + t->tqent_taskq = NULL; +} +EXPORT_SYMBOL(taskq_init_ent); + +/* + * Return the next pending task, preference is given to tasks on the + * priority list which were dispatched with TQ_FRONT. + */ +static taskq_ent_t * +taskq_next_ent(taskq_t *tq) +{ + struct list_head *list; + + if (!list_empty(&tq->tq_prio_list)) + list = &tq->tq_prio_list; + else if (!list_empty(&tq->tq_pend_list)) + list = &tq->tq_pend_list; + else + return (NULL); + + return (list_entry(list->next, taskq_ent_t, tqent_list)); +} + +/* + * Spawns a new thread for the specified taskq. + */ +static void +taskq_thread_spawn_task(void *arg) +{ + taskq_t *tq = (taskq_t *)arg; + unsigned long flags; + + if (taskq_thread_create(tq) == NULL) { + /* restore spawning count if failed */ + spin_lock_irqsave_nested(&tq->tq_lock, flags, + tq->tq_lock_class); + tq->tq_nspawn--; + spin_unlock_irqrestore(&tq->tq_lock, flags); + } +} + +/* + * Spawn addition threads for dynamic taskqs (TASKQ_DYNAMIC) the current + * number of threads is insufficient to handle the pending tasks. These + * new threads must be created by the dedicated dynamic_taskq to avoid + * deadlocks between thread creation and memory reclaim. The system_taskq + * which is also a dynamic taskq cannot be safely used for this. + */ +static int +taskq_thread_spawn(taskq_t *tq) +{ + int spawning = 0; + + if (!(tq->tq_flags & TASKQ_DYNAMIC)) + return (0); + + if ((tq->tq_nthreads + tq->tq_nspawn < tq->tq_maxthreads) && + (tq->tq_flags & TASKQ_ACTIVE)) { + spawning = (++tq->tq_nspawn); + taskq_dispatch(dynamic_taskq, taskq_thread_spawn_task, + tq, TQ_NOSLEEP); + } + + return (spawning); +} + +/* + * Threads in a dynamic taskq should only exit once it has been completely + * drained and no other threads are actively servicing tasks. This prevents + * threads from being created and destroyed more than is required. + * + * The first thread is the thread list is treated as the primary thread. + * There is nothing special about the primary thread but in order to avoid + * all the taskq pids from changing we opt to make it long running. + */ +static int +taskq_thread_should_stop(taskq_t *tq, taskq_thread_t *tqt) +{ + if (!(tq->tq_flags & TASKQ_DYNAMIC)) + return (0); + + if (list_first_entry(&(tq->tq_thread_list), taskq_thread_t, + tqt_thread_list) == tqt) + return (0); + + return + ((tq->tq_nspawn == 0) && /* No threads are being spawned */ + (tq->tq_nactive == 0) && /* No threads are handling tasks */ + (tq->tq_nthreads > 1) && /* More than 1 thread is running */ + (!taskq_next_ent(tq)) && /* There are no pending tasks */ + (spl_taskq_thread_dynamic)); /* Dynamic taskqs are allowed */ +} + +static int +taskq_thread(void *args) +{ + DECLARE_WAITQUEUE(wait, current); + sigset_t blocked; + taskq_thread_t *tqt = args; + taskq_t *tq; + taskq_ent_t *t; + int seq_tasks = 0; + unsigned long flags; + taskq_ent_t dup_task = {}; + + ASSERT(tqt); + ASSERT(tqt->tqt_tq); + tq = tqt->tqt_tq; + current->flags |= PF_NOFREEZE; + + (void) spl_fstrans_mark(); + + sigfillset(&blocked); + sigprocmask(SIG_BLOCK, &blocked, NULL); + flush_signals(current); + + tsd_set(taskq_tsd, tq); + spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class); + /* + * If we are dynamically spawned, decrease spawning count. Note that + * we could be created during taskq_create, in which case we shouldn't + * do the decrement. But it's fine because taskq_create will reset + * tq_nspawn later. + */ + if (tq->tq_flags & TASKQ_DYNAMIC) + tq->tq_nspawn--; + + /* Immediately exit if more threads than allowed were created. */ + if (tq->tq_nthreads >= tq->tq_maxthreads) + goto error; + + tq->tq_nthreads++; + list_add_tail(&tqt->tqt_thread_list, &tq->tq_thread_list); + wake_up(&tq->tq_wait_waitq); + set_current_state(TASK_INTERRUPTIBLE); + + while (!kthread_should_stop()) { + + if (list_empty(&tq->tq_pend_list) && + list_empty(&tq->tq_prio_list)) { + + if (taskq_thread_should_stop(tq, tqt)) { + wake_up_all(&tq->tq_wait_waitq); + break; + } + + add_wait_queue_exclusive(&tq->tq_work_waitq, &wait); + spin_unlock_irqrestore(&tq->tq_lock, flags); + + schedule(); + seq_tasks = 0; + + spin_lock_irqsave_nested(&tq->tq_lock, flags, + tq->tq_lock_class); + remove_wait_queue(&tq->tq_work_waitq, &wait); + } else { + __set_current_state(TASK_RUNNING); + } + + if ((t = taskq_next_ent(tq)) != NULL) { + list_del_init(&t->tqent_list); + + /* + * A TQENT_FLAG_PREALLOC task may be reused or freed + * during the task function call. Store tqent_id and + * tqent_flags here. + * + * Also use an on stack taskq_ent_t for tqt_task + * assignment in this case. We only populate the two + * fields used by the only user in taskq proc file. + */ + tqt->tqt_id = t->tqent_id; + tqt->tqt_flags = t->tqent_flags; + + if (t->tqent_flags & TQENT_FLAG_PREALLOC) { + dup_task.tqent_func = t->tqent_func; + dup_task.tqent_arg = t->tqent_arg; + t = &dup_task; + } + tqt->tqt_task = t; + + taskq_insert_in_order(tq, tqt); + tq->tq_nactive++; + spin_unlock_irqrestore(&tq->tq_lock, flags); + + /* Perform the requested task */ + t->tqent_func(t->tqent_arg); + + spin_lock_irqsave_nested(&tq->tq_lock, flags, + tq->tq_lock_class); + tq->tq_nactive--; + list_del_init(&tqt->tqt_active_list); + tqt->tqt_task = NULL; + + /* For prealloc'd tasks, we don't free anything. */ + if (!(tqt->tqt_flags & TQENT_FLAG_PREALLOC)) + task_done(tq, t); + + /* + * When the current lowest outstanding taskqid is + * done calculate the new lowest outstanding id + */ + if (tq->tq_lowest_id == tqt->tqt_id) { + tq->tq_lowest_id = taskq_lowest_id(tq); + ASSERT3S(tq->tq_lowest_id, >, tqt->tqt_id); + } + + /* Spawn additional taskq threads if required. */ + if ((++seq_tasks) > spl_taskq_thread_sequential && + taskq_thread_spawn(tq)) + seq_tasks = 0; + + tqt->tqt_id = TASKQID_INVALID; + tqt->tqt_flags = 0; + wake_up_all(&tq->tq_wait_waitq); + } else { + if (taskq_thread_should_stop(tq, tqt)) + break; + } + + set_current_state(TASK_INTERRUPTIBLE); + + } + + __set_current_state(TASK_RUNNING); + tq->tq_nthreads--; + list_del_init(&tqt->tqt_thread_list); +error: + kmem_free(tqt, sizeof (taskq_thread_t)); + spin_unlock_irqrestore(&tq->tq_lock, flags); + + tsd_set(taskq_tsd, NULL); + + return (0); +} + +static taskq_thread_t * +taskq_thread_create(taskq_t *tq) +{ + static int last_used_cpu = 0; + taskq_thread_t *tqt; + + tqt = kmem_alloc(sizeof (*tqt), KM_PUSHPAGE); + INIT_LIST_HEAD(&tqt->tqt_thread_list); + INIT_LIST_HEAD(&tqt->tqt_active_list); + tqt->tqt_tq = tq; + tqt->tqt_id = TASKQID_INVALID; + + tqt->tqt_thread = spl_kthread_create(taskq_thread, tqt, + "%s", tq->tq_name); + if (tqt->tqt_thread == NULL) { + kmem_free(tqt, sizeof (taskq_thread_t)); + return (NULL); + } + + if (spl_taskq_thread_bind) { + last_used_cpu = (last_used_cpu + 1) % num_online_cpus(); + kthread_bind(tqt->tqt_thread, last_used_cpu); + } + + if (spl_taskq_thread_priority) + set_user_nice(tqt->tqt_thread, PRIO_TO_NICE(tq->tq_pri)); + + wake_up_process(tqt->tqt_thread); + + return (tqt); +} + +taskq_t * +taskq_create(const char *name, int nthreads, pri_t pri, + int minalloc, int maxalloc, uint_t flags) +{ + taskq_t *tq; + taskq_thread_t *tqt; + int count = 0, rc = 0, i; + unsigned long irqflags; + + ASSERT(name != NULL); + ASSERT(minalloc >= 0); + ASSERT(maxalloc <= INT_MAX); + ASSERT(!(flags & (TASKQ_CPR_SAFE))); /* Unsupported */ + + /* Scale the number of threads using nthreads as a percentage */ + if (flags & TASKQ_THREADS_CPU_PCT) { + ASSERT(nthreads <= 100); + ASSERT(nthreads >= 0); + nthreads = MIN(nthreads, 100); + nthreads = MAX(nthreads, 0); + nthreads = MAX((num_online_cpus() * nthreads) / 100, 1); + } + + tq = kmem_alloc(sizeof (*tq), KM_PUSHPAGE); + if (tq == NULL) + return (NULL); + + spin_lock_init(&tq->tq_lock); + INIT_LIST_HEAD(&tq->tq_thread_list); + INIT_LIST_HEAD(&tq->tq_active_list); + tq->tq_name = strdup(name); + tq->tq_nactive = 0; + tq->tq_nthreads = 0; + tq->tq_nspawn = 0; + tq->tq_maxthreads = nthreads; + tq->tq_pri = pri; + tq->tq_minalloc = minalloc; + tq->tq_maxalloc = maxalloc; + tq->tq_nalloc = 0; + tq->tq_flags = (flags | TASKQ_ACTIVE); + tq->tq_next_id = TASKQID_INITIAL; + tq->tq_lowest_id = TASKQID_INITIAL; + INIT_LIST_HEAD(&tq->tq_free_list); + INIT_LIST_HEAD(&tq->tq_pend_list); + INIT_LIST_HEAD(&tq->tq_prio_list); + INIT_LIST_HEAD(&tq->tq_delay_list); + init_waitqueue_head(&tq->tq_work_waitq); + init_waitqueue_head(&tq->tq_wait_waitq); + tq->tq_lock_class = TQ_LOCK_GENERAL; + INIT_LIST_HEAD(&tq->tq_taskqs); + + if (flags & TASKQ_PREPOPULATE) { + spin_lock_irqsave_nested(&tq->tq_lock, irqflags, + tq->tq_lock_class); + + for (i = 0; i < minalloc; i++) + task_done(tq, task_alloc(tq, TQ_PUSHPAGE | TQ_NEW, + &irqflags)); + + spin_unlock_irqrestore(&tq->tq_lock, irqflags); + } + + if ((flags & TASKQ_DYNAMIC) && spl_taskq_thread_dynamic) + nthreads = 1; + + for (i = 0; i < nthreads; i++) { + tqt = taskq_thread_create(tq); + if (tqt == NULL) + rc = 1; + else + count++; + } + + /* Wait for all threads to be started before potential destroy */ + wait_event(tq->tq_wait_waitq, tq->tq_nthreads == count); + /* + * taskq_thread might have touched nspawn, but we don't want them to + * because they're not dynamically spawned. So we reset it to 0 + */ + tq->tq_nspawn = 0; + + if (rc) { + taskq_destroy(tq); + tq = NULL; + } else { + down_write(&tq_list_sem); + tq->tq_instance = taskq_find_by_name(name) + 1; + list_add_tail(&tq->tq_taskqs, &tq_list); + up_write(&tq_list_sem); + } + + return (tq); +} +EXPORT_SYMBOL(taskq_create); + +void +taskq_destroy(taskq_t *tq) +{ + struct task_struct *thread; + taskq_thread_t *tqt; + taskq_ent_t *t; + unsigned long flags; + + ASSERT(tq); + spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class); + tq->tq_flags &= ~TASKQ_ACTIVE; + spin_unlock_irqrestore(&tq->tq_lock, flags); + + /* + * When TASKQ_ACTIVE is clear new tasks may not be added nor may + * new worker threads be spawned for dynamic taskq. + */ + if (dynamic_taskq != NULL) + taskq_wait_outstanding(dynamic_taskq, 0); + + taskq_wait(tq); + + /* remove taskq from global list used by the kstats */ + down_write(&tq_list_sem); + list_del(&tq->tq_taskqs); + up_write(&tq_list_sem); + + spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class); + /* wait for spawning threads to insert themselves to the list */ + while (tq->tq_nspawn) { + spin_unlock_irqrestore(&tq->tq_lock, flags); + schedule_timeout_interruptible(1); + spin_lock_irqsave_nested(&tq->tq_lock, flags, + tq->tq_lock_class); + } + + /* + * Signal each thread to exit and block until it does. Each thread + * is responsible for removing itself from the list and freeing its + * taskq_thread_t. This allows for idle threads to opt to remove + * themselves from the taskq. They can be recreated as needed. + */ + while (!list_empty(&tq->tq_thread_list)) { + tqt = list_entry(tq->tq_thread_list.next, + taskq_thread_t, tqt_thread_list); + thread = tqt->tqt_thread; + spin_unlock_irqrestore(&tq->tq_lock, flags); + + kthread_stop(thread); + + spin_lock_irqsave_nested(&tq->tq_lock, flags, + tq->tq_lock_class); + } + + while (!list_empty(&tq->tq_free_list)) { + t = list_entry(tq->tq_free_list.next, taskq_ent_t, tqent_list); + + ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC)); + + list_del_init(&t->tqent_list); + task_free(tq, t); + } + + ASSERT0(tq->tq_nthreads); + ASSERT0(tq->tq_nalloc); + ASSERT0(tq->tq_nspawn); + ASSERT(list_empty(&tq->tq_thread_list)); + ASSERT(list_empty(&tq->tq_active_list)); + ASSERT(list_empty(&tq->tq_free_list)); + ASSERT(list_empty(&tq->tq_pend_list)); + ASSERT(list_empty(&tq->tq_prio_list)); + ASSERT(list_empty(&tq->tq_delay_list)); + + spin_unlock_irqrestore(&tq->tq_lock, flags); + + strfree(tq->tq_name); + kmem_free(tq, sizeof (taskq_t)); +} +EXPORT_SYMBOL(taskq_destroy); + + +static unsigned int spl_taskq_kick = 0; + +/* + * 2.6.36 API Change + * module_param_cb is introduced to take kernel_param_ops and + * module_param_call is marked as obsolete. Also set and get operations + * were changed to take a 'const struct kernel_param *'. + */ +static int +#ifdef module_param_cb +param_set_taskq_kick(const char *val, const struct kernel_param *kp) +#else +param_set_taskq_kick(const char *val, struct kernel_param *kp) +#endif +{ + int ret; + taskq_t *tq; + taskq_ent_t *t; + unsigned long flags; + + ret = param_set_uint(val, kp); + if (ret < 0 || !spl_taskq_kick) + return (ret); + /* reset value */ + spl_taskq_kick = 0; + + down_read(&tq_list_sem); + list_for_each_entry(tq, &tq_list, tq_taskqs) { + spin_lock_irqsave_nested(&tq->tq_lock, flags, + tq->tq_lock_class); + /* Check if the first pending is older than 5 seconds */ + t = taskq_next_ent(tq); + if (t && time_after(jiffies, t->tqent_birth + 5*HZ)) { + (void) taskq_thread_spawn(tq); + printk(KERN_INFO "spl: Kicked taskq %s/%d\n", + tq->tq_name, tq->tq_instance); + } + spin_unlock_irqrestore(&tq->tq_lock, flags); + } + up_read(&tq_list_sem); + return (ret); +} + +#ifdef module_param_cb +static const struct kernel_param_ops param_ops_taskq_kick = { + .set = param_set_taskq_kick, + .get = param_get_uint, +}; +module_param_cb(spl_taskq_kick, ¶m_ops_taskq_kick, &spl_taskq_kick, 0644); +#else +module_param_call(spl_taskq_kick, param_set_taskq_kick, param_get_uint, + &spl_taskq_kick, 0644); +#endif +MODULE_PARM_DESC(spl_taskq_kick, + "Write nonzero to kick stuck taskqs to spawn more threads"); + +int +spl_taskq_init(void) +{ + tsd_create(&taskq_tsd, NULL); + + system_taskq = taskq_create("spl_system_taskq", MAX(boot_ncpus, 64), + maxclsyspri, boot_ncpus, INT_MAX, TASKQ_PREPOPULATE|TASKQ_DYNAMIC); + if (system_taskq == NULL) + return (1); + + system_delay_taskq = taskq_create("spl_delay_taskq", MAX(boot_ncpus, 4), + maxclsyspri, boot_ncpus, INT_MAX, TASKQ_PREPOPULATE|TASKQ_DYNAMIC); + if (system_delay_taskq == NULL) { + taskq_destroy(system_taskq); + return (1); + } + + dynamic_taskq = taskq_create("spl_dynamic_taskq", 1, + maxclsyspri, boot_ncpus, INT_MAX, TASKQ_PREPOPULATE); + if (dynamic_taskq == NULL) { + taskq_destroy(system_taskq); + taskq_destroy(system_delay_taskq); + return (1); + } + + /* + * This is used to annotate tq_lock, so + * taskq_dispatch -> taskq_thread_spawn -> taskq_dispatch + * does not trigger a lockdep warning re: possible recursive locking + */ + dynamic_taskq->tq_lock_class = TQ_LOCK_DYNAMIC; + + return (0); +} + +void +spl_taskq_fini(void) +{ + taskq_destroy(dynamic_taskq); + dynamic_taskq = NULL; + + taskq_destroy(system_delay_taskq); + system_delay_taskq = NULL; + + taskq_destroy(system_taskq); + system_taskq = NULL; + + tsd_destroy(&taskq_tsd); +} |