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
|
/****************************************************************************
* sched/pthread/pthread_mutexlock.c
*
* Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <unistd.h>
#include <pthread.h>
#include <sched.h>
#include <errno.h>
#include <debug.h>
#include "pthread/pthread.h"
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: pthread_mutex_lock
*
* Description:
* The mutex object referenced by mutex is locked by calling
* pthread_mutex_lock(). If the mutex is already locked, the calling thread
* blocks until the mutex becomes available. This operation returns with the
* mutex object referenced by mutex in the locked state with the calling
* thread as its owner.
*
* If the mutex type is PTHREAD_MUTEX_NORMAL, deadlock detection is not
* provided. Attempting to relock the mutex causes deadlock. If a thread
* attempts to unlock a mutex that it has not locked or a mutex which is
* unlocked, undefined behavior results.
*
* If the mutex type is PTHREAD_MUTEX_ERRORCHECK, then error checking is
* provided. If a thread attempts to relock a mutex that it has already
* locked, an error will be returned. If a thread attempts to unlock a
* mutex that it has not locked or a mutex which is unlocked, an error will
* be returned.
*
* If the mutex type is PTHREAD_MUTEX_RECURSIVE, then the mutex maintains
* the concept of a lock count. When a thread successfully acquires a mutex
* for the first time, the lock count is set to one. Every time a thread
* relocks this mutex, the lock count is incremented by one. Each time the
* thread unlocks the mutex, the lock count is decremented by one. When the
* lock count reaches zero, the mutex becomes available for other threads to
* acquire. If a thread attempts to unlock a mutex that it has not locked or
* a mutex which is unlocked, an error will be returned.
*
* If a signal is delivered to a thread waiting for a mutex, upon return
* from the signal handler the thread resumes waiting for the mutex as if
* it was not interrupted.
*
* Parameters:
* mutex - A reference to the mutex to be locked.
*
* Return Value:
* 0 on success or an errno value on failure. Note that the errno EINTR
* is never returned by pthread_mutex_lock().
*
* Assumptions:
*
****************************************************************************/
int pthread_mutex_lock(FAR pthread_mutex_t *mutex)
{
int mypid = (int)getpid();
int ret = OK;
sdbg("mutex=0x%p\n", mutex);
if (!mutex)
{
ret = EINVAL;
}
else
{
/* Make sure the semaphore is stable while we make the following
* checks. This all needs to be one atomic action.
*/
sched_lock();
/* Does this task already hold the semaphore? */
if (mutex->pid == mypid)
{
/* Yes.. Is this a recursive mutex? */
#ifdef CONFIG_MUTEX_TYPES
if (mutex->type == PTHREAD_MUTEX_RECURSIVE)
{
/* Yes... just increment the number of locks held and return success */
mutex->nlocks++;
}
else
#endif
{
/* No, then we would deadlock... return an error (default behavior
* is like PTHREAD_MUTEX_ERRORCHECK)
*/
sdbg("Returning EDEADLK\n");
ret = EDEADLK;
}
}
else
{
/* Take the semaphore */
ret = pthread_takesemaphore((sem_t*)&mutex->sem);
/* If we succussfully obtained the semaphore, then indicate
* that we own it.
*/
if (!ret)
{
mutex->pid = mypid;
#ifdef CONFIG_MUTEX_TYPES
mutex->nlocks = 1;
#endif
}
}
sched_unlock();
}
sdbg("Returning %d\n", ret);
return ret;
}
|
