aboutsummaryrefslogtreecommitdiffstats
path: root/src/it_msgq.c
blob: dd28034f00b215f0a0f563617d83508d525bc155 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
/*! \file it_msgq.c
 * Osmocom Inter-Thread message 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_msgq
 *  @{
 *  Inter-Thread Message Queue.
 *
 * This implements a general-purpose message queue between threads. It
 * uses 'struct msgb' as elements in the queue and an eventfd-based notification
 * mechanism.  Hence, it can be used for pretty much anything that can be stored
 * inside msgbs, including msgb-wrapped osmo_prim.
 *
 * The idea is that the sending thread simply calls osmo_it_msgq_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 msgb
 * 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/msgb.h>
#include <osmocom/core/it_msgq.h>

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(msg_queues);
static pthread_rwlock_t msg_queues_rwlock;

static struct osmo_it_msgq *_osmo_it_msgq_by_name(const char *name)
{
	struct osmo_it_msgq *q;
	llist_for_each_entry(q, &msg_queues, entry) {
		if (!strcmp(q->name, name))
			return q;
	}
	return NULL;
}

struct osmo_it_msgq *osmo_it_msgq_by_name(const char *name)
{
	struct osmo_it_msgq *q;
	pthread_rwlock_rdlock(&msg_queues_rwlock);
	q = _osmo_it_msgq_by_name(name);
	pthread_rwlock_unlock(&msg_queues_rwlock);
	return q;
}

/* osmo_fd call-back when eventfd is readable */
static int osmo_it_msgq_fd_cb(struct osmo_fd *ofd, unsigned int what)
{
	struct osmo_it_msgq *q = (struct osmo_it_msgq *) 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 msgb *msg = osmo_it_msgq_dequeue(q);
		/* in case the user might have called osmo_it_msgq_flush() we may
		 * end up in the eventfd-dispatch but witout any messages left in the queue,
		 * otherwise I'd have loved to OSMO_ASSERT(msg) here. */
		if (!msg)
			break;
		q->read_cb(q, msg);
	}

	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
 *  \returns a newly-allocated inter-thread message queue; NULL in case of error */
struct osmo_it_msgq *osmo_it_msgq_alloc(void *ctx, const char *name, unsigned int max_length,
					void (*read_cb)(struct osmo_it_msgq *q, struct msgb *msg),
					void *data)
{
	struct osmo_it_msgq *q;
	int fd;

	q = talloc_zero(ctx, struct osmo_it_msgq);
	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);

	/* create eventfd */
	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 ot */
	osmo_fd_setup(&q->event_ofd, fd, OSMO_FD_READ, osmo_it_msgq_fd_cb, q, 0);

	/* add to global list of queues, checking for duplicate names */
	pthread_rwlock_wrlock(&msg_queues_rwlock);
	if (_osmo_it_msgq_by_name(q->name)) {
		pthread_rwlock_unlock(&msg_queues_rwlock);
		osmo_fd_close(&q->event_ofd);
		talloc_free(q);
		return NULL;
	}
	llist_add_tail(&q->entry, &msg_queues);
	pthread_rwlock_unlock(&msg_queues_rwlock);

	return q;
}

/*! Flush all messages currently present in queue */
static void _osmo_it_msgq_flush(struct osmo_it_msgq *q)
{
	struct msgb *msg;
	while ((msg = msgb_dequeue_count(&q->list, &q->current_length))) {
		msgb_free(msg);
	}
}

/*! Flush all messages currently present in queue */
void osmo_it_msgq_flush(struct osmo_it_msgq *q)
{
	pthread_mutex_lock(&q->mutex);
	_osmo_it_msgq_flush(q);
	pthread_mutex_unlock(&q->mutex);
}

/*! Destroy a message queue */
void osmo_it_msgq_destroy(struct osmo_it_msgq *q)
{
	/* first remove from global list of queues */
	pthread_rwlock_wrlock(&msg_queues_rwlock);
	llist_del(&q->entry);
	pthread_rwlock_unlock(&msg_queues_rwlock);
	/* next, close the eventfd */
	osmo_fd_close(&q->event_ofd);
	/* flush all messages still present */
	osmo_it_msgq_flush(q);
	/* 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] msgb Message buffer to enqueue
 *  \returns 0 on success; negative on error */
int osmo_it_msgq_enqueue(struct osmo_it_msgq *queue, struct msgb *msg)
{
	pthread_mutex_lock(&queue->mutex);
	if (queue->current_length+1 > queue->max_length) {
		pthread_mutex_unlock(&queue->mutex);
		return -ENOSPC;
	}
	msgb_enqueue_count(&queue->list, msg, &queue->current_length);
	pthread_mutex_unlock(&queue->mutex);
	/* increment eventfd counter by one */
	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 msgb *osmo_it_msgq_dequeue(struct osmo_it_msgq *queue)
{
	struct msgb *msg;

	pthread_mutex_lock(&queue->mutex);
	msg = msgb_dequeue_count(&queue->list, &queue->current_length);
	pthread_mutex_unlock(&queue->mutex);

	return msg;
}

#endif /* HAVE_SYS_EVENTFD_H */

/*! @} */