Question

Linux内核中pthread_mutex_lock和pthread_cond_wait的等价物是什么。以及如何使用它们。你能否提供简单的（hello world）例子。

Answer 1

您不能在内核空间中使用任何库调用，因为内核模块直接链接到内核。

您可以使用：

mutex_lock()＆amp; mutex_unlock()

通过以下方式提供： linux/mutex.h

Answer 2

对于互斥体（如Als所说）：

mutex_lock()和mutex_unlock()我们应该在使用mutex_init()（来自#include <linux/mutex.h>）之前启用互斥锁

相当于pthread_cond_wait

wait_event_interruptible()和wake_up_interruptible()我们应该使用init_waitqueue_head()（来自#include <linux/wait.h>）

初始化wait_queue_head

Answer 3

我很久以前（1999-ish）为Linux内核编程创建了一个互斥和条件库，并用于各种项目。

我称之为LMC（linux互斥和条件变量）。这是在内核中存在互斥类型之前。

http://www.kylheku.com/~kaz/lmc.html

最近，我添加了一个很酷的新函数，其语义是“放弃互斥量等待条件变量，和同时轮询多个文件描述符，直到给定的超时。”< / p>

我在内核线程中使用了这个内核线程，它监视各种共享对象的更新，并且同时与内核套接字通信。

检查出来：

/**
 * Atomically give up the mutex and wait on the condition variable.
 * Wake up if the specified timeout elapses, or if a signal is delivered.
 * Additionally, also wait on the specified file descriptors to become
 * ready, combining condition waiting with poll().
 * KCOND_WAIT_SUCCESS means the condition was signaled, or one or more
 * file descriptors are ready.
 * Also, a negative value can be returned indicating an error!
 * (The poll needs to dynamically allocate some memory for the wait table).
 * The timeout is relative to the current time, specifying how long to sleep in
 * jiffies (CPU clock ticks).
 */
int kcond_timed_wait_rel_poll(kcond_t *, kmutex_t *, long, 
                              kcond_poll_t *, unsigned int);

kcond_poll_t结构数组是您必须创建并填充自己的结构，结构如下所示。有一个类型字段，因此您可以等待套接字（struct socket *）或文件（struct file *）：

/**
 * Structure for file-descriptor polling condition waits.
 * This resembles struct pollfd, but uses a direct file descriptor
 * pointer rather than a file descriptor number.  Also,
 * it contains the wait queue by which the process is enqueued
 * to wait on that descriptor. Thus our poll function doesn't
 * have to dynamically allocate wait queue tables. It gets
 * them from this array! (But this means that the array cannot
 * be used by multiple threads at the same time to do polling!)
 */
typedef struct {
        kcond_poll_type_t type;  /* Must set this. */
        union {                 /* Must set union field according to type. */
                struct file *file;      
                struct socket *sock;
        } obj;
        short events;           /* And this. */
        short revents;          /* Check response in this. */
        wait_queue_t wait;          /* Internal, don't set. */
        wait_queue_head_t *queue;   /* Internal, don't set */
} kcond_poll_t;

在linux内核中等效于pthread_mutex_lock和pthread_cond_wait

3 个答案: