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
229
230
231
232
233
234
235
236
237/****************************************************************************
* fs/semaphore/sem_open.c
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/stat.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdarg.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <sched.h>
#include <assert.h>
#include <errno.h>
#include <nuttx/kmalloc.h>
#include <nuttx/semaphore.h>
#include <nuttx/fs/fs.h>
#include "inode/inode.h"
#include "vfs/vfs.h"
#include "semaphore/semaphore.h"
#ifdef CONFIG_FS_NAMED_SEMAPHORES
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxsem_open
*
* Description:
* This function establishes a connection between named semaphores and a
* task. Following a call to sem_open() with the semaphore name, the task
* may reference the semaphore associated with name using the address
* returned by this call. The semaphore may be used in subsequent calls
* to sem_wait(), sem_trywait(), and sem_post(). The semaphore remains
* usable until the semaphore is closed by a successful call to
* sem_close().
*
* If a task makes multiple calls to sem_open() with the same name, then
* the same semaphore address is returned (provided there have been no
* calls to sem_unlink()).
*
* Input Parameters:
* sem - Location to return the semaphore reference.
* name - Semaphore name.
* oflags - Semaphore creation options. This may either or both of the
* following bit settings.
* oflags = 0: Connect to the semaphore only if it already exists.
* oflags = O_CREAT: Connect to the semaphore if it exists, otherwise
* create the semaphore.
* oflags = O_CREAT|O_EXCL: Create a new semaphore
* unless one of this name already exists.
* Optional parameters. When the O_CREAT flag is specified, two optional
* parameters are expected:
* 1. mode_t mode, and
* 2. unsigned int value. This initial value of the semaphore. Valid
* initial values of the semaphore must be less than or equal to
* SEM_VALUE_MAX.
*
* Returned Value:
* 0 (OK), or negated errno if unsuccessful.
*
* Assumptions:
*
****************************************************************************/
int nxsem_open(FAR sem_t **sem, FAR const char *name, int oflags, ...)
{
FAR struct inode *inode;
FAR struct nsem_inode_s *nsem;
struct inode_search_s desc;
char fullpath[MAX_SEMPATH];
mode_t mode;
unsigned value;
int ret;
/* Get the full path to the semaphore */
snprintf(fullpath, MAX_SEMPATH,
CONFIG_FS_NAMED_SEMAPHORES_VFS_PATH "/%s", name);
/* Get the inode for this semaphore. This should succeed if the
* semaphore has already been created. In this case, inode_find()
* will have incremented the reference count on the inode.
*/
SETUP_SEARCH(&desc, fullpath, false);
ret = inode_find(&desc);
if (ret >= 0)
{
/* Something exists at this path. Get the search results */
inode = desc.node;
/* Verify that the inode is a semaphore */
if (!INODE_IS_NAMEDSEM(inode))
{
ret = -ENXIO;
goto errout_with_inode;
}
/* It exists and is a semaphore. Check if the caller wanted to
* create a new semaphore with this name.
*/
if ((oflags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
{
ret = -EEXIST;
goto errout_with_inode;
}
/* Return a reference to the semaphore, retaining the reference
* count on the inode.
*/
*sem = &inode->u.i_nsem->ns_sem;
}
else
{
va_list ap;
/* The semaphore does not exists. Were we asked to create it? */
if ((oflags & O_CREAT) == 0)
{
/* The semaphore does not exist and O_CREAT is not set */
ret = -ENOENT;
goto errout_with_search;
}
/* Create the semaphore. First we have to extract the additional
* parameters from the variable argument list.
* REVISIT: Mode parameter is not currently used.
*/
va_start(ap, oflags);
mode = va_arg(ap, mode_t) & ~getumask();
value = va_arg(ap, unsigned);
va_end(ap);
/* Check the semaphore value */
if (value > SEM_VALUE_MAX)
{
ret = -EINVAL;
goto errout_with_search;
}
/* Create an inode in the pseudo-filesystem at this path. The new
* inode will be created with a reference count of zero.
*/
inode_lock();
ret = inode_reserve(fullpath, mode, &inode);
inode_unlock();
if (ret < 0)
{
goto errout_with_search;
}
/* Allocate the semaphore structure (using the appropriate allocator
* for the group)
*/
nsem = group_malloc(NULL, sizeof(struct nsem_inode_s));
if (!nsem)
{
ret = -ENOMEM;
goto errout_with_inode;
}
/* Link to the inode */
inode->u.i_nsem = nsem;
nsem->ns_inode = inode;
/* Initialize the inode */
INODE_SET_NAMEDSEM(inode);
atomic_fetch_add(&inode->i_crefs, 1);
/* Initialize the semaphore */
nxsem_init(&nsem->ns_sem, 0, value);
/* Return a reference to the semaphore */
*sem = &nsem->ns_sem;
}
RELEASE_SEARCH(&desc);
#ifdef CONFIG_FS_NOTIFY
notify_open(fullpath, oflags);
#endif
return OK;
errout_with_inode:
inode_release(inode);
errout_with_search:
RELEASE_SEARCH(&desc);
return ret;
}
#endif /* CONFIG_FS_NAMED_SEMAPHORES */