| /*! \file it_q.c |
| * Osmocom Inter-Thread queue implementation */ |
| /* (C) 2019 by Harald Welte <laforge@gnumonks.org> |
| * All Rights Reserved. |
| * |
| * SPDX-License-Identifier: GPL-2.0+ |
| * |
| * This program 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. |
| * |
| * This program 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. |
| */ |
| |
| /*! \addtogroup it_q |
| * @{ |
| * Inter-Thread Message Queue. |
| * |
| * This implements a general-purpose queue between threads. It uses |
| * user-provided data types (containing a llist_head as initial member) |
| * as elements in the queue and an eventfd-based notification mechanism. |
| * Hence, it can be used for pretty much anything, including but not |
| * limited to msgbs, including msgb-wrapped osmo_prim. |
| * |
| * The idea is that the sending thread simply calls osmo_it_q_enqueue(). |
| * The receiving thread is woken up from its osmo_select_main() loop by eventfd, |
| * and a general osmo_fd callback function for the eventfd will dequeue each item |
| * and call a queue-specific callback function. |
| */ |
| |
| #include "config.h" |
| |
| #ifdef HAVE_SYS_EVENTFD_H |
| |
| #include <pthread.h> |
| #include <unistd.h> |
| #include <string.h> |
| #include <errno.h> |
| #include <sys/eventfd.h> |
| |
| #include <osmocom/core/linuxlist.h> |
| #include <osmocom/core/talloc.h> |
| #include <osmocom/core/utils.h> |
| #include <osmocom/core/it_q.h> |
| |
| /* "increment" the eventfd by specified 'inc' */ |
| static int eventfd_increment(int fd, uint64_t inc) |
| { |
| int rc; |
| |
| rc = write(fd, &inc, sizeof(inc)); |
| if (rc != sizeof(inc)) |
| return -1; |
| |
| return 0; |
| } |
| |
| /* global (for all threads) list of message queues in a program + associated lock */ |
| static LLIST_HEAD(it_queues); |
| static pthread_rwlock_t it_queues_rwlock = PTHREAD_RWLOCK_INITIALIZER; |
| |
| /* resolve it-queue by its [globally unique] name; must be called with rwlock held */ |
| static struct osmo_it_q *_osmo_it_q_by_name(const char *name) |
| { |
| struct osmo_it_q *q; |
| llist_for_each_entry(q, &it_queues, entry) { |
| if (!strcmp(q->name, name)) |
| return q; |
| } |
| return NULL; |
| } |
| |
| /*! resolve it-queue by its [globally unique] name */ |
| struct osmo_it_q *osmo_it_q_by_name(const char *name) |
| { |
| struct osmo_it_q *q; |
| pthread_rwlock_rdlock(&it_queues_rwlock); |
| q = _osmo_it_q_by_name(name); |
| pthread_rwlock_unlock(&it_queues_rwlock); |
| return q; |
| } |
| |
| /* osmo_fd call-back when eventfd is readable */ |
| static int osmo_it_q_fd_cb(struct osmo_fd *ofd, unsigned int what) |
| { |
| struct osmo_it_q *q = (struct osmo_it_q *) ofd->data; |
| uint64_t val; |
| int i, rc; |
| |
| if (!(what & OSMO_FD_READ)) |
| return 0; |
| |
| rc = read(ofd->fd, &val, sizeof(val)); |
| if (rc < sizeof(val)) |
| return rc; |
| |
| for (i = 0; i < val; i++) { |
| struct llist_head *item = _osmo_it_q_dequeue(q); |
| /* in case the user might have called osmo_it_q_flush() we may |
| * end up in the eventfd-dispatch but without any messages left in the queue, |
| * otherwise I'd have loved to OSMO_ASSERT(msg) here. */ |
| if (!item) |
| break; |
| q->read_cb(q, item); |
| } |
| |
| return 0; |
| } |
| |
| /*! Allocate a new inter-thread message queue. |
| * \param[in] ctx talloc context from which to allocate the queue |
| * \param[in] name human-readable string name of the queue; function creates a copy. |
| * \param[in] read_cb call-back function to be called for each de-queued message; may be |
| * NULL in case you don't want eventfd/osmo_select integration and |
| * will manually take care of noticing if and when to dequeue. |
| * \returns a newly-allocated inter-thread message queue; NULL in case of error */ |
| struct osmo_it_q *osmo_it_q_alloc(void *ctx, const char *name, unsigned int max_length, |
| void (*read_cb)(struct osmo_it_q *q, struct llist_head *item), |
| void *data) |
| { |
| struct osmo_it_q *q; |
| int fd; |
| |
| q = talloc_zero(ctx, struct osmo_it_q); |
| if (!q) |
| return NULL; |
| q->data = data; |
| q->name = talloc_strdup(q, name); |
| q->current_length = 0; |
| q->max_length = max_length; |
| q->read_cb = read_cb; |
| INIT_LLIST_HEAD(&q->list); |
| pthread_mutex_init(&q->mutex, NULL); |
| q->event_ofd.fd = -1; |
| |
| if (q->read_cb) { |
| /* create eventfd *if* the user has provided a read_cb function */ |
| fd = eventfd(0, 0); |
| if (fd < 0) { |
| talloc_free(q); |
| return NULL; |
| } |
| |
| /* initialize BUT NOT REGISTER the osmo_fd. The receiving thread must |
| * take are to select/poll/read/... on it */ |
| osmo_fd_setup(&q->event_ofd, fd, OSMO_FD_READ, osmo_it_q_fd_cb, q, 0); |
| } |
| |
| /* add to global list of queues, checking for duplicate names */ |
| pthread_rwlock_wrlock(&it_queues_rwlock); |
| if (_osmo_it_q_by_name(q->name)) { |
| pthread_rwlock_unlock(&it_queues_rwlock); |
| if (q->event_ofd.fd >= 0) |
| osmo_fd_close(&q->event_ofd); |
| talloc_free(q); |
| return NULL; |
| } |
| llist_add_tail(&q->entry, &it_queues); |
| pthread_rwlock_unlock(&it_queues_rwlock); |
| |
| return q; |
| } |
| |
| static void *item_dequeue(struct llist_head *queue) |
| { |
| struct llist_head *lh; |
| |
| if (llist_empty(queue)) |
| return NULL; |
| |
| lh = queue->next; |
| if (lh) { |
| llist_del(lh); |
| return lh; |
| } else |
| return NULL; |
| } |
| |
| /*! Flush all messages currently present in queue */ |
| static void _osmo_it_q_flush(struct osmo_it_q *q) |
| { |
| void *item; |
| while ((item = item_dequeue(&q->list))) { |
| talloc_free(item); |
| } |
| q->current_length = 0; |
| } |
| |
| /*! Flush all messages currently present in queue */ |
| void osmo_it_q_flush(struct osmo_it_q *q) |
| { |
| OSMO_ASSERT(q); |
| |
| pthread_mutex_lock(&q->mutex); |
| _osmo_it_q_flush(q); |
| pthread_mutex_unlock(&q->mutex); |
| } |
| |
| /*! Destroy a message queue */ |
| void osmo_it_q_destroy(struct osmo_it_q *q) |
| { |
| OSMO_ASSERT(q); |
| |
| /* first remove from global list of queues */ |
| pthread_rwlock_wrlock(&it_queues_rwlock); |
| llist_del(&q->entry); |
| pthread_rwlock_unlock(&it_queues_rwlock); |
| /* next, close the eventfd */ |
| if (q->event_ofd.fd >= 0) |
| osmo_fd_close(&q->event_ofd); |
| /* flush all messages still present */ |
| osmo_it_q_flush(q); |
| pthread_mutex_destroy(&q->mutex); |
| /* and finally release memory */ |
| talloc_free(q); |
| } |
| |
| /*! Thread-safe en-queue to an inter-thread message queue. |
| * \param[in] queue Inter-thread queue on which to enqueue |
| * \param[in] item Item to enqueue. Must have llist_head as first member! |
| * \returns 0 on success; negative on error */ |
| int _osmo_it_q_enqueue(struct osmo_it_q *queue, struct llist_head *item) |
| { |
| OSMO_ASSERT(queue); |
| OSMO_ASSERT(item); |
| |
| pthread_mutex_lock(&queue->mutex); |
| if (queue->current_length+1 > queue->max_length) { |
| pthread_mutex_unlock(&queue->mutex); |
| return -ENOSPC; |
| } |
| llist_add_tail(item, &queue->list); |
| queue->current_length++; |
| pthread_mutex_unlock(&queue->mutex); |
| /* increment eventfd counter by one */ |
| if (queue->event_ofd.fd >= 0) |
| eventfd_increment(queue->event_ofd.fd, 1); |
| return 0; |
| } |
| |
| |
| /*! Thread-safe de-queue from an inter-thread message queue. |
| * \param[in] queue Inter-thread queue from which to dequeue |
| * \returns dequeued message buffer; NULL if none available |
| */ |
| struct llist_head *_osmo_it_q_dequeue(struct osmo_it_q *queue) |
| { |
| struct llist_head *l; |
| OSMO_ASSERT(queue); |
| |
| pthread_mutex_lock(&queue->mutex); |
| |
| if (llist_empty(&queue->list)) |
| l = NULL; |
| l = queue->list.next; |
| OSMO_ASSERT(l); |
| llist_del(l); |
| queue->current_length--; |
| |
| pthread_mutex_unlock(&queue->mutex); |
| |
| return l; |
| } |
| |
| |
| #endif /* HAVE_SYS_EVENTFD_H */ |
| |
| /*! @} */ |