vss: Check the afs socket either for reading or for writing.
[paraslash.git] / ipc.c
1 /*
2 * Copyright (C) 2006-2008 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file ipc.c interprocess communication and shared memory helpers */
8
9 #include "para.h"
10 #include "error.h"
11 #include "ipc.h"
12 #include <sys/ipc.h>
13 #include <sys/shm.h>
14 #include <sys/sem.h>
15
16 /**
17 * define a new mutex
18 *
19 * \return the identifier for the new mutex on success, \a -E_SEM_GET
20 * on errors.
21 *
22 * \sa semget(2)
23 */
24 int mutex_new(void)
25 {
26 int ret = semget(IPC_PRIVATE, 1, IPC_CREAT | 0666);
27 return ret < 0? -E_SEM_GET : ret;
28 }
29
30 /**
31 * destroy a mutex
32 *
33 * \param id the identifier of the mutex to be destroyed
34 *
35 * \return Positive on success, \a -E_SEM_REMOVE on errors.
36 *
37 * \sa semctl(2)
38 */
39 int mutex_destroy(int id)
40 {
41 int ret = semctl(id, 0, IPC_RMID);
42 return ret < 0? -E_SEM_REMOVE : 1;
43 }
44
45 static void para_semop(int id, struct sembuf *sops, int num)
46 {
47 do {
48 if (semop(id, sops, num) >= 0)
49 return;
50 } while (errno == EINTR);
51 if (errno == EIDRM) {
52 PARA_NOTICE_LOG("semaphore set %d was removed\n", id);
53 return;
54 }
55 PARA_EMERG_LOG("fatal semop error %s: pid %d\n", strerror(errno),
56 (int)getpid());
57 exit(EXIT_FAILURE);
58 }
59
60 /**
61 * lock the given mutex
62 *
63 * \param id of the shared memory area to lock
64 *
65 * This function either succeeds or aborts.
66 *
67 * \sa semop(2), struct misc_meta_data
68 */
69 void mutex_lock(int id)
70 {
71 struct sembuf sops[2] = {
72 {
73 .sem_num = 0,
74 .sem_op = 0,
75 .sem_flg = SEM_UNDO
76 },
77 {
78 .sem_num = 0,
79 .sem_op = 1,
80 .sem_flg = SEM_UNDO
81 }
82 };
83 para_semop(id, sops, 2);
84 }
85
86 /**
87 * unlock a mutex
88 *
89 * \param id the identifier of the mutex
90 *
91 * This function either succeeds or aborts.
92 *
93 * \sa semop(2), struct misc_meta_data
94 */
95 void mutex_unlock(int id)
96 {
97 struct sembuf sops[1] = {
98 {
99 .sem_num = 0,
100 .sem_op = -1,
101 .sem_flg = SEM_UNDO
102 },
103 };
104 para_semop(id, sops, 1);
105 }
106
107 /**
108 * create a new shared memory area of given size
109 *
110 * \param size the size of the shared memory area to create
111 *
112 * \return The id of the shared memory areay on success, \a -E_SHM_GET on errors.
113 *
114 * \sa shmget(2)
115 */
116 int shm_new(size_t size)
117 {
118 int ret = shmget(IPC_PRIVATE, size, IPC_CREAT | IPC_EXCL | 0600);
119 return ret < 0 ? -E_SHM_GET : ret;
120 }
121
122 /**
123 * destroy the given shared memory area
124 *
125 * \param id the shared memory id
126 *
127 * \return The return value of the underlying shmctl() call on success,
128 * \a -E_SHM_DESTROY on errors.
129 *
130 * \sa shmctl(2)
131 */
132 int shm_destroy(int id)
133 {
134 struct shmid_ds shm_desc;
135 int ret = shmctl(id, IPC_RMID, &shm_desc);
136 return ret < 0? -E_SHM_DESTROY : ret;
137 }
138
139 /**
140 * attach a shared memory segment
141 *
142 * \param id the identifier of the shared memory segment to attach
143 * \param mode either ATTACH_RO (read only) or ATTACH_RW (read/write)
144 * \param result points to the attached area just attached
145 *
146 * \return positive on success, \a -E_SHM_ATTACH on errors.
147 *
148 * \sa shmat(2)
149 */
150 int shm_attach(int id, enum shm_attach_mode mode, void **result)
151 {
152 if (mode == ATTACH_RW) {
153 *result = shmat(id, NULL, 0);
154 return *result? 1 : -E_SHM_ATTACH;
155 }
156 *result = shmat(id, NULL, SHM_RDONLY);
157 return *result? 1 : -E_SHM_ATTACH;
158 }
159
160 /**
161 * detach a shared memory segment
162 *
163 * \param addr the address of the attached segment
164 *
165 * \return positive on success, \a -E_SHM_DETACH on errors.
166 *
167 * \sa shmdt(2)
168 */
169 int shm_detach(void *addr)
170 {
171 int ret = shmdt(addr);
172 return ret < 0? -E_SHM_DETACH : 1;
173 }