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Diffstat (limited to 'src/it_q.c')
-rw-r--r-- | src/it_q.c | 277 |
1 files changed, 277 insertions, 0 deletions
diff --git a/src/it_q.c b/src/it_q.c new file mode 100644 index 00000000..1bb0e155 --- /dev/null +++ b/src/it_q.c @@ -0,0 +1,277 @@ +/*! \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. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, + * MA 02110-1301, USA. + */ + +/*! \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 */ + +/*! @} */ |