错误：隐式声明函数‘init_MUTEX’ [-Werror=implicit-function-declaration]

最新推荐文章于 2023-05-10 10:54:18 发布

最新推荐文章于 2023-05-10 10:54:18 发布 · 235 阅读

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#操作系统

本文详细介绍了Linux内核中Semaphore的定义与使用方法，包括init_MUTEX宏定义的变化及sema_init函数的应用。Semaphore用于同步访问共享资源，防止多个任务同时访问。

在新版本的linux内核中，init_mutex已经被废除了，新版本使用sema_init函数。查了一下早期版本的定义：

平台：X86 32位

内核：2.6.30

定义：

Linux/include/linux/semaphore.h


 1 /*
 2 * Copyright (c) 2008 Intel Corporation
 3 * Author: Matthew Wilcox <willy@linux.intel.com>
 4 *
 5 * Distributed under the terms of the GNU GPL, version 2
 6 *
 7 * Please see kernel/semaphore.c for documentation of these functions
 8 */
 9 #ifndef __LINUX_SEMAPHORE_H
10 #define __LINUX_SEMAPHORE_H
11
12 #include <linux/list.h>
13 #include <linux/spinlock.h>
14
15 /* Please don't access any members of this structure directly */
16 struct semaphore {
17     spinlock_t       lock;
18     unsigned int      count;
19     struct list_head    wait_list;
20 };
21
22 #define __SEMAPHORE_INITIALIZER(name, n)                \
23 {                                    \
24     .lock      = __SPIN_LOCK_UNLOCKED((name).lock),      \
25     .count     = n,                      \
26     .wait_list   = LIST_HEAD_INIT((name).wait_list),       \
27 }
28
29 #define DECLARE_MUTEX(name)   \
30     struct semaphore name = __SEMAPHORE_INITIALIZER(name, 1)
31
32 static inline void sema_init(struct semaphore *sem, int val)
33 {
34     static struct lock_class_key __key;
35     *sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val);
36     lockdep_init_map(&sem->lock.dep_map, "semaphore->lock", &__key, 0);
37 }
38
39 #define init_MUTEX(sem)     sema_init(sem, 1)//在最新的版本中没有这两个宏定义了
40 #define init_MUTEX_LOCKED(sem) sema_init(sem, 0)
41
42 extern void down(struct semaphore *sem);
43 extern int __must_check down_interruptible(struct semaphore *sem);
44 extern int __must_check down_killable(struct semaphore *sem);
45 extern int __must_check down_trylock(struct semaphore *sem);
46 extern int __must_check down_timeout(struct semaphore *sem, long jiffies);
47 extern void up(struct semaphore *sem);
48
49 #endif /* __LINUX_SEMAPHORE_H */
50

说明：Init_MUTEX()函数初始化信号量为互斥量。互斥量为信号量的特例，它可以防止数据被两个不同系统调用读写。

sema_init (sem, 1) 定义为：

平台：X86 32位

内核：3.0.xx

定义：

Linux/include/linux/semaphore.h


 1 /*
 2 * Copyright (c) 2008 Intel Corporation
 3 * Author: Matthew Wilcox <willy@linux.intel.com>
 4 *
 5 * Distributed under the terms of the GNU GPL, version 2
 6 *
 7 * Please see kernel/semaphore.c for documentation of these functions
 8 */
 9 #ifndef __LINUX_SEMAPHORE_H
10 #define __LINUX_SEMAPHORE_H
11
12 #include <linux/list.h>
13 #include <linux/spinlock.h>
14
15 /* Please don't access any members of this structure directly */
16 struct semaphore {
17     spinlock_t       lock;
18     unsigned int      count;
19     struct list_head    wait_list;
20 };
21
22 #define __SEMAPHORE_INITIALIZER(name, n)                \
23 {                                    \
24     .lock      = __SPIN_LOCK_UNLOCKED((name).lock),      \
25     .count     = n,                      \
26     .wait_list   = LIST_HEAD_INIT((name).wait_list),       \
27 }
28
29 #define DEFINE_SEMAPHORE(name) \
30     struct semaphore name = __SEMAPHORE_INITIALIZER(name, 1)
31
32 static inline void sema_init(struct semaphore *sem, int val)
33 {
34     static struct lock_class_key __key;
35     *sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val);
36     lockdep_init_map(&sem->lock.dep_map, "semaphore->lock", &__key, 0);
37 }
38
39 extern void down(struct semaphore *sem);
40 extern int __must_check down_interruptible(struct semaphore *sem);
41 extern int __must_check down_killable(struct semaphore *sem);
42 extern int __must_check down_trylock(struct semaphore *sem);
43 extern int __must_check down_timeout(struct semaphore *sem, long jiffies);
44 extern void up(struct semaphore *sem);
45
46 #endif /* __LINUX_SEMAPHORE_H */
47