1 /******************************************************************************
2 *
3 * Copyright (C) 2014 Google, Inc.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at:
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 ******************************************************************************/
18
19 #define LOG_TAG "bt_osi_semaphore"
20
21 #include "osi/include/semaphore.h"
22
23 #include <assert.h>
24 #include <errno.h>
25 #include <fcntl.h>
26 #include <malloc.h>
27 #include <string.h>
28 #include <sys/eventfd.h>
29 #include <unistd.h>
30
31 #include "osi/include/allocator.h"
32 #include "osi/include/log.h"
33 #include "osi/include/osi.h"
34
35 #if !defined(EFD_SEMAPHORE)
36 # define EFD_SEMAPHORE (1 << 0)
37 #endif
38
39 struct semaphore_t {
40 int fd;
41 };
42
semaphore_new(unsigned int value)43 semaphore_t *semaphore_new(unsigned int value) {
44 semaphore_t *ret = osi_malloc(sizeof(semaphore_t));
45 ret->fd = eventfd(value, EFD_SEMAPHORE);
46 if (ret->fd == INVALID_FD) {
47 LOG_ERROR(LOG_TAG, "%s unable to allocate semaphore: %s", __func__, strerror(errno));
48 osi_free(ret);
49 ret = NULL;
50 }
51 return ret;
52 }
53
semaphore_free(semaphore_t * semaphore)54 void semaphore_free(semaphore_t *semaphore) {
55 if (!semaphore)
56 return;
57
58 if (semaphore->fd != INVALID_FD)
59 close(semaphore->fd);
60 osi_free(semaphore);
61 }
62
semaphore_wait(semaphore_t * semaphore)63 void semaphore_wait(semaphore_t *semaphore) {
64 assert(semaphore != NULL);
65 assert(semaphore->fd != INVALID_FD);
66
67 eventfd_t value;
68 if (eventfd_read(semaphore->fd, &value) == -1)
69 LOG_ERROR(LOG_TAG, "%s unable to wait on semaphore: %s", __func__, strerror(errno));
70 }
71
semaphore_try_wait(semaphore_t * semaphore)72 bool semaphore_try_wait(semaphore_t *semaphore) {
73 assert(semaphore != NULL);
74 assert(semaphore->fd != INVALID_FD);
75
76 int flags = fcntl(semaphore->fd, F_GETFL);
77 if (flags == -1) {
78 LOG_ERROR(LOG_TAG, "%s unable to get flags for semaphore fd: %s", __func__, strerror(errno));
79 return false;
80 }
81 if (fcntl(semaphore->fd, F_SETFL, flags | O_NONBLOCK) == -1) {
82 LOG_ERROR(LOG_TAG, "%s unable to set O_NONBLOCK for semaphore fd: %s", __func__, strerror(errno));
83 return false;
84 }
85
86 bool rc = true;
87 eventfd_t value;
88 if (eventfd_read(semaphore->fd, &value) == -1)
89 rc = false;
90
91 if (fcntl(semaphore->fd, F_SETFL, flags) == -1)
92 LOG_ERROR(LOG_TAG, "%s unable to restore flags for semaphore fd: %s", __func__, strerror(errno));
93 return rc;
94 }
95
semaphore_post(semaphore_t * semaphore)96 void semaphore_post(semaphore_t *semaphore) {
97 assert(semaphore != NULL);
98 assert(semaphore->fd != INVALID_FD);
99
100 if (eventfd_write(semaphore->fd, 1ULL) == -1)
101 LOG_ERROR(LOG_TAG, "%s unable to post to semaphore: %s", __func__, strerror(errno));
102 }
103
semaphore_get_fd(const semaphore_t * semaphore)104 int semaphore_get_fd(const semaphore_t *semaphore) {
105 assert(semaphore != NULL);
106 assert(semaphore->fd != INVALID_FD);
107 return semaphore->fd;
108 }
109