/*****************************************************************************\ * 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 . * UCRL-CODE-235197 * * This file is part of the SPL, Solaris Porting Layer. * For details, see . * * 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 . ***************************************************************************** * Solaris Porting Layer (SPL) Task Queue Implementation. \*****************************************************************************/ #include #include #include #ifdef SS_DEBUG_SUBSYS #undef SS_DEBUG_SUBSYS #endif #define SS_DEBUG_SUBSYS SS_TASKQ /* Global system-wide dynamic task queue available for all consumers */ taskq_t *system_taskq; EXPORT_SYMBOL(system_taskq); 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; } /* * 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) { taskq_ent_t *t; int count = 0; SENTRY; ASSERT(tq); ASSERT(spin_is_locked(&tq->tq_lock)); 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)); list_del_init(&t->tqent_list); SRETURN(t); } /* Free list is empty and memory allocations are prohibited */ if (flags & TQ_NOALLOC) SRETURN(NULL); /* Hit maximum taskq_ent_t pool size */ if (tq->tq_nalloc >= tq->tq_maxalloc) { if (flags & TQ_NOSLEEP) SRETURN(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_entq_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, tq->tq_lock_flags); schedule_timeout(HZ / 100); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); if (count < 100) SGOTO(retry, count++); } spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); t = kmem_alloc(sizeof(taskq_ent_t), task_km_flags(flags)); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); if (t) { taskq_init_ent(t); tq->tq_nalloc++; } SRETURN(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) { SENTRY; ASSERT(tq); ASSERT(t); ASSERT(spin_is_locked(&tq->tq_lock)); ASSERT(list_empty(&t->tqent_list)); kmem_free(t, sizeof(taskq_ent_t)); tq->tq_nalloc--; SEXIT; } /* * 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) { SENTRY; ASSERT(tq); ASSERT(t); ASSERT(spin_is_locked(&tq->tq_lock)); list_del_init(&t->tqent_list); if (tq->tq_nalloc <= tq->tq_minalloc) { t->tqent_id = 0; 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); } SEXIT; } /* * As tasks are submitted to the task queue they are assigned a * monotonically increasing taskqid and added to the tail of the pending * list. As worker threads become available the tasks are removed from * the head of the pending or priority list, giving preference to the * priority list. The tasks are then removed from their respective * list, and the taskq_thread servicing the task is added to the active * list, preserving the order using the serviced task's taskqid. * Finally, as tasks complete the taskq_thread servicing the task is * removed from the active list. This means that the pending task and * active taskq_thread lists are always kept sorted by taskqid. Thus the * lowest outstanding incomplete taskqid can be determined simply by * checking the min taskqid for each head item on the pending, priority, * and active taskq_thread list. This value is stored in * tq->tq_lowest_id and only updated to the new lowest id when the * previous lowest id completes. All taskqids lower than * tq->tq_lowest_id must have completed. It is also possible larger * taskqid's have completed because they may be processed in parallel by * several worker threads. However, this is not a problem because the * behavior of taskq_wait_id() is to block until all previously * submitted taskqid's have completed. * * XXX: Taskqid_t wrapping is not handled. However, taskqid_t's are * 64-bit values so even if a taskq is processing 2^24 (16,777,216) * taskqid_ts per second it will still take 2^40 seconds, 34,865 years, * before the wrap occurs. I can live with that for now. */ static int taskq_wait_check(taskq_t *tq, taskqid_t id) { int rc; spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); rc = (id < tq->tq_lowest_id); spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); SRETURN(rc); } void __taskq_wait_id(taskq_t *tq, taskqid_t id) { SENTRY; ASSERT(tq); wait_event(tq->tq_wait_waitq, taskq_wait_check(tq, id)); SEXIT; } EXPORT_SYMBOL(__taskq_wait_id); void __taskq_wait(taskq_t *tq) { taskqid_t id; SENTRY; ASSERT(tq); /* Wait for the largest outstanding taskqid */ spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); id = tq->tq_next_id - 1; spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); __taskq_wait_id(tq, id); SEXIT; } EXPORT_SYMBOL(__taskq_wait); int __taskq_member(taskq_t *tq, void *t) { struct list_head *l; taskq_thread_t *tqt; SENTRY; ASSERT(tq); ASSERT(t); list_for_each(l, &tq->tq_thread_list) { tqt = list_entry(l, taskq_thread_t, tqt_thread_list); if (tqt->tqt_thread == (struct task_struct *)t) SRETURN(1); } SRETURN(0); } EXPORT_SYMBOL(__taskq_member); taskqid_t __taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags) { taskq_ent_t *t; taskqid_t rc = 0; SENTRY; ASSERT(tq); ASSERT(func); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); /* Taskq being destroyed and all tasks drained */ if (!(tq->tq_flags & TQ_ACTIVE)) SGOTO(out, rc = 0); /* 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)) SGOTO(out, rc = 0); if ((t = task_alloc(tq, flags)) == NULL) SGOTO(out, rc = 0); spin_lock(&t->tqent_lock); /* 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 = rc = tq->tq_next_id; tq->tq_next_id++; t->tqent_func = func; t->tqent_arg = arg; ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC)); spin_unlock(&t->tqent_lock); wake_up(&tq->tq_work_waitq); out: spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); SRETURN(rc); } EXPORT_SYMBOL(__taskq_dispatch); void __taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags, taskq_ent_t *t) { SENTRY; ASSERT(tq); ASSERT(func); ASSERT(!(tq->tq_flags & TASKQ_DYNAMIC)); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); /* Taskq being destroyed and all tasks drained */ if (!(tq->tq_flags & TQ_ACTIVE)) { t->tqent_id = 0; goto out; } spin_lock(&t->tqent_lock); /* * 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; spin_unlock(&t->tqent_lock); wake_up(&tq->tq_work_waitq); out: spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); SEXIT; } 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_LIST_HEAD(&t->tqent_list); t->tqent_id = 0; t->tqent_func = NULL; t->tqent_arg = NULL; t->tqent_flags = 0; } EXPORT_SYMBOL(__taskq_init_ent); /* * Returns the lowest incomplete taskqid_t. The taskqid_t may * be queued on the pending list, on the priority 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; SENTRY; ASSERT(tq); ASSERT(spin_is_locked(&tq->tq_lock)); 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_active_list)) { tqt = list_entry(tq->tq_active_list.next, taskq_thread_t, tqt_active_list); ASSERT(tqt->tqt_id != 0); lowest_id = MIN(lowest_id, tqt->tqt_id); } SRETURN(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; SENTRY; ASSERT(tq); ASSERT(tqt); ASSERT(spin_is_locked(&tq->tq_lock)); 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); SEXIT; } 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; struct list_head *pend_list; SENTRY; ASSERT(tqt); tq = tqt->tqt_tq; current->flags |= PF_NOFREEZE; sigfillset(&blocked); sigprocmask(SIG_BLOCK, &blocked, NULL); flush_signals(current); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); tq->tq_nthreads++; 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)) { add_wait_queue_exclusive(&tq->tq_work_waitq, &wait); spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); schedule(); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); remove_wait_queue(&tq->tq_work_waitq, &wait); } else { __set_current_state(TASK_RUNNING); } if (!list_empty(&tq->tq_prio_list)) pend_list = &tq->tq_prio_list; else if (!list_empty(&tq->tq_pend_list)) pend_list = &tq->tq_pend_list; else pend_list = NULL; if (pend_list) { t = list_entry(pend_list->next, taskq_ent_t, tqent_list); list_del_init(&t->tqent_list); /* In order to support recursively dispatching a * preallocated taskq_ent_t, tqent_id must be * stored prior to executing tqent_func. */ tqt->tqt_id = t->tqent_id; /* We must store a copy of the flags prior to * servicing the task (servicing a prealloc'd task * returns the ownership of the tqent back to * the caller of taskq_dispatch). Thus, * tqent_flags _may_ change within the call. */ tqt->tqt_flags = t->tqent_flags; taskq_insert_in_order(tq, tqt); tq->tq_nactive++; spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); /* Perform the requested task */ t->tqent_func(t->tqent_arg); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); tq->tq_nactive--; list_del_init(&tqt->tqt_active_list); /* For prealloc'd tasks, we don't free anything. */ if ((tq->tq_flags & TASKQ_DYNAMIC) || !(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); } tqt->tqt_id = 0; tqt->tqt_flags = 0; wake_up_all(&tq->tq_wait_waitq); } set_current_state(TASK_INTERRUPTIBLE); } __set_current_state(TASK_RUNNING); tq->tq_nthreads--; list_del_init(&tqt->tqt_thread_list); kmem_free(tqt, sizeof(taskq_thread_t)); spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); SRETURN(0); } 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 rc = 0, i, j = 0; SENTRY; ASSERT(name != NULL); ASSERT(pri <= maxclsyspri); ASSERT(minalloc >= 0); ASSERT(maxalloc <= INT_MAX); ASSERT(!(flags & (TASKQ_CPR_SAFE | TASKQ_DYNAMIC))); /* 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) SRETURN(NULL); spin_lock_init(&tq->tq_lock); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); INIT_LIST_HEAD(&tq->tq_thread_list); INIT_LIST_HEAD(&tq->tq_active_list); tq->tq_name = name; tq->tq_nactive = 0; tq->tq_nthreads = 0; tq->tq_pri = pri; tq->tq_minalloc = minalloc; tq->tq_maxalloc = maxalloc; tq->tq_nalloc = 0; tq->tq_flags = (flags | TQ_ACTIVE); tq->tq_next_id = 1; tq->tq_lowest_id = 1; INIT_LIST_HEAD(&tq->tq_free_list); INIT_LIST_HEAD(&tq->tq_pend_list); INIT_LIST_HEAD(&tq->tq_prio_list); init_waitqueue_head(&tq->tq_work_waitq); init_waitqueue_head(&tq->tq_wait_waitq); if (flags & TASKQ_PREPOPULATE) for (i = 0; i < minalloc; i++) task_done(tq, task_alloc(tq, TQ_PUSHPAGE | TQ_NEW)); spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); for (i = 0; i < nthreads; i++) { 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 = 0; tqt->tqt_thread = kthread_create(taskq_thread, tqt, "%s/%d", name, i); if (tqt->tqt_thread) { list_add(&tqt->tqt_thread_list, &tq->tq_thread_list); kthread_bind(tqt->tqt_thread, i % num_online_cpus()); set_user_nice(tqt->tqt_thread, PRIO_TO_NICE(pri)); wake_up_process(tqt->tqt_thread); j++; } else { kmem_free(tqt, sizeof(taskq_thread_t)); rc = 1; } } /* Wait for all threads to be started before potential destroy */ wait_event(tq->tq_wait_waitq, tq->tq_nthreads == j); if (rc) { __taskq_destroy(tq); tq = NULL; } SRETURN(tq); } EXPORT_SYMBOL(__taskq_create); void __taskq_destroy(taskq_t *tq) { struct task_struct *thread; taskq_thread_t *tqt; taskq_ent_t *t; SENTRY; ASSERT(tq); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); tq->tq_flags &= ~TQ_ACTIVE; spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); /* TQ_ACTIVE cleared prevents new tasks being added to pending */ __taskq_wait(tq); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); /* * 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, tq->tq_lock_flags); kthread_stop(thread); spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags); } 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); } ASSERT(tq->tq_nthreads == 0); ASSERT(tq->tq_nalloc == 0); 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)); spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags); kmem_free(tq, sizeof(taskq_t)); SEXIT; } EXPORT_SYMBOL(__taskq_destroy); int spl_taskq_init(void) { SENTRY; /* Solaris creates a dynamic taskq of up to 64 threads, however in * a Linux environment 1 thread per-core is usually about right */ system_taskq = taskq_create("spl_system_taskq", num_online_cpus(), minclsyspri, 4, 512, TASKQ_PREPOPULATE); if (system_taskq == NULL) SRETURN(1); SRETURN(0); } void spl_taskq_fini(void) { SENTRY; taskq_destroy(system_taskq); SEXIT; }