1 | /* Copyright 2002, Red Hat Inc. */ |
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2 | |
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3 | #include <mqueue.h> |
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4 | #include <fcntl.h> |
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5 | #include <unistd.h> |
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6 | #include <errno.h> |
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7 | #include <sys/stat.h> |
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8 | #include <sys/mman.h> |
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9 | #include <sys/ipc.h> |
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10 | #include <sys/sem.h> |
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11 | #include <string.h> |
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12 | #include <stdlib.h> |
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13 | #include <time.h> |
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14 | #include <stdarg.h> |
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15 | #include <machine/weakalias.h> |
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16 | #define _LIBC 1 |
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17 | #include <sys/lock.h> |
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18 | #undef _LIBC |
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19 | |
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20 | #include "mqlocal.h" |
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21 | |
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22 | #define NHASH 32 /* Num of hash lists, must be a power of 2 */ |
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23 | #define LOCHASH(i) ((i)&(NHASH-1)) |
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24 | |
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25 | static long mq_index; /* Index of next entry */ |
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26 | static struct libc_mq *mq_hash[NHASH]; /* Hash list heads for mqopen_infos */ |
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27 | |
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28 | __LOCK_INIT(static, mq_hash_lock); |
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29 | |
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30 | mqd_t |
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31 | mq_open (const char *name, int oflag, ...) |
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32 | { |
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33 | MSG *wrbuf = NULL; |
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34 | MSG *rdbuf = NULL; |
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35 | int msgqid = -1; |
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36 | int rc = -1; |
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37 | int fd = -1; |
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38 | int semid = -1; |
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39 | int created = 0; |
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40 | key_t key = (key_t)-1; |
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41 | struct mq_attr *attr = (struct mq_attr *)MAP_FAILED; |
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42 | struct sembuf sb = {0, 0, 0}; |
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43 | mode_t mode = 0; |
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44 | int size; |
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45 | int i, index, saved_errno; |
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46 | char *real_name; |
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47 | char *ptr; |
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48 | struct mq_attr *user_attr = NULL; |
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49 | struct libc_mq *info; |
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50 | union semun arg; |
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51 | |
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52 | /* ignore opening slash if present */ |
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53 | if (*name == '/') |
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54 | ++name; |
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55 | size = strlen(name); |
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56 | |
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57 | if ((real_name = (char *)malloc (size + sizeof(MSGQ_PREFIX))) == NULL || |
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58 | (info = (struct libc_mq *)malloc (sizeof(struct libc_mq))) == NULL) |
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59 | { |
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60 | errno = ENOSPC; |
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61 | if (real_name) |
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62 | free (real_name); |
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63 | return (mqd_t)-1; |
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64 | } |
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65 | |
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66 | /* use given name to create shared memory file name - we convert any |
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67 | slashes to underscores so we don't have to create directories */ |
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68 | memcpy (real_name, MSGQ_PREFIX, sizeof(MSGQ_PREFIX) - 1); |
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69 | memcpy (real_name + sizeof(MSGQ_PREFIX) - 1, name, size + 1); |
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70 | ptr = real_name + sizeof(MSGQ_PREFIX) - 1; |
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71 | for (i = 0; i < size; ++i) |
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72 | { |
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73 | if (*ptr == '/') |
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74 | *ptr = '_'; |
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75 | ++ptr; |
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76 | } |
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77 | |
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78 | /* open shared memory file based on msg queue open flags and then use memory |
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79 | file to create a unique key to use for semaphores, etc.. */ |
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80 | if (oflag & O_CREAT) |
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81 | { |
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82 | va_list list; |
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83 | va_start (list, oflag); |
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84 | |
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85 | saved_errno = errno; |
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86 | mode = (mode_t)va_arg (list, int); |
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87 | user_attr = va_arg(list,struct mq_attr *); |
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88 | va_end (list); |
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89 | |
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90 | /* attempt to open the shared memory file for exclusive create so we know |
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91 | whether we are the owners or not */ |
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92 | fd = open (real_name, O_RDWR | O_CREAT | O_EXCL, mode); |
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93 | if (fd < 0 && (oflag & O_EXCL)) |
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94 | { |
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95 | /* we failed and the user wanted exclusive create */ |
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96 | free (real_name); |
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97 | free (info); |
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98 | return (mqd_t)-1; |
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99 | } |
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100 | errno = saved_errno; |
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101 | /* check if we created the file or not */ |
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102 | if (fd >= 0) |
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103 | created = 1; |
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104 | } |
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105 | |
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106 | if (fd < 0) |
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107 | fd = open (real_name, O_RDWR, 0); |
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108 | |
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109 | if (fd >= 0) |
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110 | key = ftok(real_name, 255); |
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111 | |
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112 | if (key != (key_t)-1) |
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113 | /* memory map the shared memory file so we have a global shared data area to use */ |
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114 | attr = (struct mq_attr *)mmap (0, sizeof(struct mq_attr), PROT_READ | PROT_WRITE, |
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115 | MAP_SHARED, fd, 0); |
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116 | |
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117 | if (attr != (struct mq_attr *)MAP_FAILED) |
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118 | { |
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119 | /* we need semaphores to prevent multi-process race conditions on the |
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120 | shared storage which contains a shared structure. The following |
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121 | are the ones we need. |
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122 | |
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123 | 0 = open semaphore |
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124 | 1 = number of opens |
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125 | 2 = number of writes left until queue is full |
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126 | 3 = number of reads available in queue |
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127 | 4 = notify semaphore |
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128 | 5 = number of readers */ |
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129 | arg.val = 0; |
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130 | /* make sure the creator of the shared memory file also is the creator of the |
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131 | semaphores...this will ensure that it also creates the message queue */ |
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132 | if (created) |
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133 | { |
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134 | saved_errno = errno; |
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135 | semid = semget (key, 6, IPC_CREAT | IPC_EXCL | mode); |
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136 | errno = saved_errno; |
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137 | /* now that we have created the semaphore, we should initialize it */ |
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138 | if (semid != -1) |
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139 | semctl (semid, 0, SETVAL, arg); |
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140 | } |
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141 | else |
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142 | { |
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143 | /* if we didn't create the shared memory file but have gotten to here, we want |
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144 | to ensure we haven't gotten ahead of the creator temporarily so we will |
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145 | loop until the semaphore exists. This ensures that the creator will be the |
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146 | one to create the message queue with the correct mode and we will be blocked |
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147 | by the open semaphore 0. We impose a time limit to ensure something terrible |
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148 | hasn't gone wrong. */ |
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149 | struct timespec tms; |
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150 | int i; |
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151 | |
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152 | tms.tv_sec = 0; |
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153 | tms.tv_nsec = 10000; /* 10 microseconds */ |
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154 | for (i = 0; i < 100; ++i) |
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155 | { |
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156 | if ((semid = semget (key, 6, 0)) != -1) |
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157 | break; |
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158 | /* sleep in case we our a higher priority process */ |
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159 | nanosleep (&tms, NULL); |
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160 | } |
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161 | } |
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162 | } |
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163 | |
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164 | if (semid != -1) |
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165 | { |
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166 | /* acquire main open semaphore if we didn't create it */ |
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167 | if (!created) |
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168 | { |
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169 | sb.sem_op = -1; |
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170 | rc = semop (semid, &sb, 1); |
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171 | } |
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172 | else |
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173 | rc = 0; /* need this to continue below */ |
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174 | } |
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175 | |
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176 | if (rc == 0) |
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177 | { |
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178 | if (created) |
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179 | { |
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180 | /* the creator must get here first so the message queue will be created */ |
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181 | msgqid = msgget (key, IPC_CREAT | mode); |
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182 | if (msgqid >= 0) |
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183 | { |
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184 | /* we have created the message queue so check and set the attributes */ |
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185 | if ((wrbuf = (MSG *)malloc (user_attr->mq_msgsize + sizeof(int))) == NULL || |
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186 | (rdbuf = (MSG *)malloc (user_attr->mq_msgsize + sizeof(int))) == NULL || |
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187 | user_attr == NULL || user_attr->mq_msgsize <= 0 || user_attr->mq_maxmsg <= 0) |
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188 | { |
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189 | /* we're out of space and we created the message queue so we should |
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190 | try to remove it */ |
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191 | msgctl (msgqid, IPC_RMID, NULL); |
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192 | msgqid = -1; /* allow clean up to occur below */ |
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193 | if (wrbuf && rdbuf) |
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194 | errno = EINVAL; |
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195 | else |
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196 | errno = ENOSPC; |
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197 | } |
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198 | else /* valid attributes */ |
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199 | { |
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200 | write (fd, user_attr, sizeof(struct mq_attr)); |
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201 | attr->mq_curmsgs = 0; |
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202 | attr->mq_flags = oflag & O_NONBLOCK; |
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203 | arg.val = 0; |
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204 | semctl (semid, 1, SETVAL, arg); /* number of opens starts at 0 */ |
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205 | semctl (semid, 3, SETVAL, arg); /* number of reads available starts at 0 */ |
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206 | semctl (semid, 5, SETVAL, arg); /* number of readers starts at 0 */ |
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207 | arg.val = 1; |
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208 | semctl (semid, 4, SETVAL, arg); /* notify semaphore */ |
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209 | arg.val = user_attr->mq_maxmsg; |
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210 | semctl (semid, 2, SETVAL, arg); /* number of writes left starts at mq_maxmsg */ |
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211 | } |
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212 | } |
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213 | } |
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214 | else /* just open it */ |
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215 | { |
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216 | msgqid = msgget (key, 0); |
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217 | wrbuf = (MSG *)malloc (attr->mq_msgsize + sizeof(int)); |
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218 | rdbuf = (MSG *)malloc (attr->mq_msgsize + sizeof(int)); |
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219 | } |
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220 | |
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221 | /* release semaphore acquired earlier */ |
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222 | sb.sem_op = 1; |
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223 | semop (semid, &sb, 1); |
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224 | } |
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225 | |
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226 | /* if we get here and we haven't got a message queue id, then we need to clean up |
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227 | our mess and return failure */ |
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228 | if (msgqid < 0) |
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229 | { |
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230 | if (fd >= 0) |
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231 | close (fd); |
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232 | if (attr != (struct mq_attr *)MAP_FAILED) |
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233 | munmap (attr, sizeof(struct mq_attr)); |
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234 | if (created) |
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235 | { |
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236 | unlink (real_name); |
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237 | if (semid != -1) |
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238 | semctl (semid, 0, IPC_RMID); |
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239 | } |
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240 | free (real_name); |
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241 | free (info); |
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242 | if (wrbuf) |
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243 | free (wrbuf); |
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244 | if (rdbuf) |
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245 | free (rdbuf); |
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246 | return (mqd_t)-1; |
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247 | } |
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248 | |
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249 | /* we are successful so register the message queue */ |
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250 | |
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251 | /* up the count of msg queue opens */ |
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252 | sb.sem_op = 1; |
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253 | sb.sem_num = 1; |
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254 | semop (semid, &sb, 1); |
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255 | |
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256 | /* success, translate into index into mq_info array */ |
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257 | __lock_acquire(mq_hash_lock); |
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258 | index = mq_index++; |
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259 | info->index = index; |
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260 | info->msgqid = msgqid; |
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261 | info->name = real_name; |
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262 | info->semid = semid; |
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263 | info->fd = fd; |
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264 | info->oflag = oflag; |
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265 | info->wrbuf = wrbuf; |
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266 | info->rdbuf = rdbuf; |
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267 | info->cleanup_notify = NULL; |
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268 | info->next = mq_hash[LOCHASH(index)]; |
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269 | info->attr = attr; |
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270 | mq_hash[LOCHASH(index)] = info; |
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271 | __lock_release(mq_hash_lock); |
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272 | |
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273 | return (mqd_t)index; |
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274 | } |
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275 | |
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276 | struct libc_mq * |
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277 | __find_mq (mqd_t mq) |
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278 | { |
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279 | struct libc_mq *ptr; |
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280 | |
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281 | __lock_acquire(mq_hash_lock); |
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282 | |
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283 | ptr = mq_hash[LOCHASH((int)mq)]; |
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284 | |
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285 | while (ptr) |
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286 | { |
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287 | if (ptr->index == (int)mq) |
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288 | break; |
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289 | ptr = ptr->next; |
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290 | } |
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291 | |
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292 | __lock_release(mq_hash_lock); |
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293 | |
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294 | return ptr; |
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295 | } |
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296 | |
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297 | void |
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298 | __cleanup_mq (mqd_t mq) |
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299 | { |
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300 | struct libc_mq *ptr; |
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301 | struct libc_mq *prev; |
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302 | int semid; |
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303 | struct sembuf sb = {0, 0, 0}; |
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304 | |
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305 | __lock_acquire(mq_hash_lock); |
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306 | |
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307 | ptr = mq_hash[LOCHASH((int)mq)]; |
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308 | prev = NULL; |
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309 | |
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310 | while (ptr) |
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311 | { |
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312 | if (ptr->index == (int)mq) |
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313 | break; |
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314 | prev = ptr; |
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315 | ptr = ptr->next; |
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316 | } |
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317 | |
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318 | if (ptr != NULL) |
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319 | { |
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320 | if (ptr->cleanup_notify != NULL) |
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321 | ptr->cleanup_notify (ptr); |
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322 | if (prev != NULL) |
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323 | prev->next = ptr->next; |
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324 | else |
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325 | mq_hash[LOCHASH((int)mq)] = NULL; |
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326 | munmap (ptr->attr, sizeof(struct mq_attr)); |
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327 | close (ptr->fd); |
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328 | free (ptr->name); |
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329 | free (ptr->wrbuf); |
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330 | free (ptr->rdbuf); |
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331 | semid = ptr->semid; |
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332 | free (ptr); |
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333 | /* lower the count of msg queue opens */ |
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334 | sb.sem_op = -1; |
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335 | sb.sem_num = 1; |
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336 | sb.sem_flg = IPC_NOWAIT; |
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337 | semop (semid, &sb, 1); |
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338 | } |
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339 | |
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340 | __lock_release(mq_hash_lock); |
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341 | } |
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342 | |
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343 | |
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344 | |
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345 | |
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346 | |
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