Harald Welte | e4cd267 | 2019-08-06 19:56:16 +0200 | [diff] [blame] | 1 | /*! \file it_q.c |
| 2 | * Osmocom Inter-Thread queue implementation */ |
| 3 | /* (C) 2019 by Harald Welte <laforge@gnumonks.org> |
| 4 | * All Rights Reserved. |
| 5 | * |
| 6 | * SPDX-License-Identifier: GPL-2.0+ |
| 7 | * |
| 8 | * This program is free software; you can redistribute it and/or modify |
| 9 | * it under the terms of the GNU General Public License as published by |
| 10 | * the Free Software Foundation; either version 2 of the License, or |
| 11 | * (at your option) any later version. |
| 12 | * |
| 13 | * This program is distributed in the hope that it will be useful, |
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 | * GNU General Public License for more details. |
Harald Welte | e4cd267 | 2019-08-06 19:56:16 +0200 | [diff] [blame] | 17 | */ |
| 18 | |
| 19 | /*! \addtogroup it_q |
| 20 | * @{ |
| 21 | * Inter-Thread Message Queue. |
| 22 | * |
| 23 | * This implements a general-purpose queue between threads. It uses |
| 24 | * user-provided data types (containing a llist_head as initial member) |
| 25 | * as elements in the queue and an eventfd-based notification mechanism. |
| 26 | * Hence, it can be used for pretty much anything, including but not |
| 27 | * limited to msgbs, including msgb-wrapped osmo_prim. |
| 28 | * |
| 29 | * The idea is that the sending thread simply calls osmo_it_q_enqueue(). |
| 30 | * The receiving thread is woken up from its osmo_select_main() loop by eventfd, |
| 31 | * and a general osmo_fd callback function for the eventfd will dequeue each item |
| 32 | * and call a queue-specific callback function. |
| 33 | */ |
| 34 | |
| 35 | #include "../config.h" |
| 36 | |
| 37 | #ifdef HAVE_SYS_EVENTFD_H |
| 38 | |
| 39 | #include <pthread.h> |
| 40 | #include <unistd.h> |
| 41 | #include <string.h> |
| 42 | #include <errno.h> |
| 43 | #include <sys/eventfd.h> |
| 44 | |
| 45 | #include <osmocom/core/linuxlist.h> |
| 46 | #include <osmocom/core/talloc.h> |
| 47 | #include <osmocom/core/utils.h> |
| 48 | #include <osmocom/core/it_q.h> |
| 49 | |
| 50 | /* "increment" the eventfd by specified 'inc' */ |
| 51 | static int eventfd_increment(int fd, uint64_t inc) |
| 52 | { |
| 53 | int rc; |
| 54 | |
| 55 | rc = write(fd, &inc, sizeof(inc)); |
| 56 | if (rc != sizeof(inc)) |
| 57 | return -1; |
| 58 | |
| 59 | return 0; |
| 60 | } |
| 61 | |
| 62 | /* global (for all threads) list of message queues in a program + associated lock */ |
| 63 | static LLIST_HEAD(it_queues); |
| 64 | static pthread_rwlock_t it_queues_rwlock = PTHREAD_RWLOCK_INITIALIZER; |
| 65 | |
| 66 | /* resolve it-queue by its [globally unique] name; must be called with rwlock held */ |
| 67 | static struct osmo_it_q *_osmo_it_q_by_name(const char *name) |
| 68 | { |
| 69 | struct osmo_it_q *q; |
| 70 | llist_for_each_entry(q, &it_queues, entry) { |
| 71 | if (!strcmp(q->name, name)) |
| 72 | return q; |
| 73 | } |
| 74 | return NULL; |
| 75 | } |
| 76 | |
| 77 | /*! resolve it-queue by its [globally unique] name */ |
| 78 | struct osmo_it_q *osmo_it_q_by_name(const char *name) |
| 79 | { |
| 80 | struct osmo_it_q *q; |
| 81 | pthread_rwlock_rdlock(&it_queues_rwlock); |
| 82 | q = _osmo_it_q_by_name(name); |
| 83 | pthread_rwlock_unlock(&it_queues_rwlock); |
| 84 | return q; |
| 85 | } |
| 86 | |
| 87 | /* osmo_fd call-back when eventfd is readable */ |
| 88 | static int osmo_it_q_fd_cb(struct osmo_fd *ofd, unsigned int what) |
| 89 | { |
| 90 | struct osmo_it_q *q = (struct osmo_it_q *) ofd->data; |
| 91 | uint64_t val; |
| 92 | int i, rc; |
| 93 | |
| 94 | if (!(what & OSMO_FD_READ)) |
| 95 | return 0; |
| 96 | |
| 97 | rc = read(ofd->fd, &val, sizeof(val)); |
| 98 | if (rc < sizeof(val)) |
| 99 | return rc; |
| 100 | |
| 101 | for (i = 0; i < val; i++) { |
| 102 | struct llist_head *item = _osmo_it_q_dequeue(q); |
| 103 | /* in case the user might have called osmo_it_q_flush() we may |
| 104 | * end up in the eventfd-dispatch but without any messages left in the queue, |
| 105 | * otherwise I'd have loved to OSMO_ASSERT(msg) here. */ |
| 106 | if (!item) |
| 107 | break; |
| 108 | q->read_cb(q, item); |
| 109 | } |
| 110 | |
| 111 | return 0; |
| 112 | } |
| 113 | |
| 114 | /*! Allocate a new inter-thread message queue. |
| 115 | * \param[in] ctx talloc context from which to allocate the queue |
| 116 | * \param[in] name human-readable string name of the queue; function creates a copy. |
| 117 | * \param[in] read_cb call-back function to be called for each de-queued message; may be |
| 118 | * NULL in case you don't want eventfd/osmo_select integration and |
| 119 | * will manually take care of noticing if and when to dequeue. |
| 120 | * \returns a newly-allocated inter-thread message queue; NULL in case of error */ |
| 121 | struct osmo_it_q *osmo_it_q_alloc(void *ctx, const char *name, unsigned int max_length, |
| 122 | void (*read_cb)(struct osmo_it_q *q, struct llist_head *item), |
| 123 | void *data) |
| 124 | { |
| 125 | struct osmo_it_q *q; |
| 126 | int fd; |
| 127 | |
| 128 | q = talloc_zero(ctx, struct osmo_it_q); |
| 129 | if (!q) |
| 130 | return NULL; |
| 131 | q->data = data; |
| 132 | q->name = talloc_strdup(q, name); |
| 133 | q->current_length = 0; |
| 134 | q->max_length = max_length; |
| 135 | q->read_cb = read_cb; |
| 136 | INIT_LLIST_HEAD(&q->list); |
| 137 | pthread_mutex_init(&q->mutex, NULL); |
| 138 | q->event_ofd.fd = -1; |
| 139 | |
| 140 | if (q->read_cb) { |
| 141 | /* create eventfd *if* the user has provided a read_cb function */ |
| 142 | fd = eventfd(0, 0); |
| 143 | if (fd < 0) { |
| 144 | talloc_free(q); |
| 145 | return NULL; |
| 146 | } |
| 147 | |
| 148 | /* initialize BUT NOT REGISTER the osmo_fd. The receiving thread must |
| 149 | * take are to select/poll/read/... on it */ |
| 150 | osmo_fd_setup(&q->event_ofd, fd, OSMO_FD_READ, osmo_it_q_fd_cb, q, 0); |
| 151 | } |
| 152 | |
| 153 | /* add to global list of queues, checking for duplicate names */ |
| 154 | pthread_rwlock_wrlock(&it_queues_rwlock); |
| 155 | if (_osmo_it_q_by_name(q->name)) { |
| 156 | pthread_rwlock_unlock(&it_queues_rwlock); |
| 157 | if (q->event_ofd.fd >= 0) |
| 158 | osmo_fd_close(&q->event_ofd); |
| 159 | talloc_free(q); |
| 160 | return NULL; |
| 161 | } |
| 162 | llist_add_tail(&q->entry, &it_queues); |
| 163 | pthread_rwlock_unlock(&it_queues_rwlock); |
| 164 | |
| 165 | return q; |
| 166 | } |
| 167 | |
| 168 | static void *item_dequeue(struct llist_head *queue) |
| 169 | { |
| 170 | struct llist_head *lh; |
| 171 | |
| 172 | if (llist_empty(queue)) |
| 173 | return NULL; |
| 174 | |
| 175 | lh = queue->next; |
| 176 | if (lh) { |
| 177 | llist_del(lh); |
| 178 | return lh; |
| 179 | } else |
| 180 | return NULL; |
| 181 | } |
| 182 | |
| 183 | /*! Flush all messages currently present in queue */ |
| 184 | static void _osmo_it_q_flush(struct osmo_it_q *q) |
| 185 | { |
| 186 | void *item; |
| 187 | while ((item = item_dequeue(&q->list))) { |
| 188 | talloc_free(item); |
| 189 | } |
| 190 | q->current_length = 0; |
| 191 | } |
| 192 | |
| 193 | /*! Flush all messages currently present in queue */ |
| 194 | void osmo_it_q_flush(struct osmo_it_q *q) |
| 195 | { |
| 196 | OSMO_ASSERT(q); |
| 197 | |
| 198 | pthread_mutex_lock(&q->mutex); |
| 199 | _osmo_it_q_flush(q); |
| 200 | pthread_mutex_unlock(&q->mutex); |
| 201 | } |
| 202 | |
| 203 | /*! Destroy a message queue */ |
| 204 | void osmo_it_q_destroy(struct osmo_it_q *q) |
| 205 | { |
| 206 | OSMO_ASSERT(q); |
| 207 | |
| 208 | /* first remove from global list of queues */ |
| 209 | pthread_rwlock_wrlock(&it_queues_rwlock); |
| 210 | llist_del(&q->entry); |
| 211 | pthread_rwlock_unlock(&it_queues_rwlock); |
| 212 | /* next, close the eventfd */ |
| 213 | if (q->event_ofd.fd >= 0) |
| 214 | osmo_fd_close(&q->event_ofd); |
| 215 | /* flush all messages still present */ |
| 216 | osmo_it_q_flush(q); |
| 217 | pthread_mutex_destroy(&q->mutex); |
| 218 | /* and finally release memory */ |
| 219 | talloc_free(q); |
| 220 | } |
| 221 | |
| 222 | /*! Thread-safe en-queue to an inter-thread message queue. |
| 223 | * \param[in] queue Inter-thread queue on which to enqueue |
| 224 | * \param[in] item Item to enqueue. Must have llist_head as first member! |
| 225 | * \returns 0 on success; negative on error */ |
| 226 | int _osmo_it_q_enqueue(struct osmo_it_q *queue, struct llist_head *item) |
| 227 | { |
| 228 | OSMO_ASSERT(queue); |
| 229 | OSMO_ASSERT(item); |
| 230 | |
| 231 | pthread_mutex_lock(&queue->mutex); |
| 232 | if (queue->current_length+1 > queue->max_length) { |
| 233 | pthread_mutex_unlock(&queue->mutex); |
| 234 | return -ENOSPC; |
| 235 | } |
| 236 | llist_add_tail(item, &queue->list); |
| 237 | queue->current_length++; |
| 238 | pthread_mutex_unlock(&queue->mutex); |
| 239 | /* increment eventfd counter by one */ |
| 240 | if (queue->event_ofd.fd >= 0) |
| 241 | eventfd_increment(queue->event_ofd.fd, 1); |
| 242 | return 0; |
| 243 | } |
| 244 | |
| 245 | |
| 246 | /*! Thread-safe de-queue from an inter-thread message queue. |
| 247 | * \param[in] queue Inter-thread queue from which to dequeue |
| 248 | * \returns dequeued message buffer; NULL if none available |
| 249 | */ |
| 250 | struct llist_head *_osmo_it_q_dequeue(struct osmo_it_q *queue) |
| 251 | { |
| 252 | struct llist_head *l; |
| 253 | OSMO_ASSERT(queue); |
| 254 | |
| 255 | pthread_mutex_lock(&queue->mutex); |
| 256 | |
| 257 | if (llist_empty(&queue->list)) |
| 258 | l = NULL; |
| 259 | l = queue->list.next; |
| 260 | OSMO_ASSERT(l); |
| 261 | llist_del(l); |
| 262 | queue->current_length--; |
| 263 | |
| 264 | pthread_mutex_unlock(&queue->mutex); |
| 265 | |
| 266 | return l; |
| 267 | } |
| 268 | |
| 269 | |
| 270 | #endif /* HAVE_SYS_EVENTFD_H */ |
| 271 | |
| 272 | /*! @} */ |