c - linux内核中pthread_mutex_lock和pthread_cond_wait的等价物

Question

什么是pthread_mutex_lock和pthread_cond_wait在linux内核中的等价物。以及如何使用它们。您能否提供简单的（hello world）示例。

Answer 1

• 对于互斥锁（正如 Als 所说）：

mutex_lock()并且mutex_unlock()我们应该在与mutex_init() (from #include <linux/mutex.h>)一起使用之前初始化互斥锁

• 相当于pthread_cond_wait

wait_event_interruptible()并且我们应该用(from )wake_up_interruptible()初始化 wait_queue_headinit_waitqueue_head()#include <linux/wait.h>

Answer 2

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()&mutex_unlock()

它们通过以下方式提供：linux/mutex.h

Answer 3

我很久以前（1999 年左右）为 Linux 内核编程制作了一个互斥锁和条件库，并在此后的各种项目中使用。

我称它为 LMC（Linux 互斥体和条件变量）。这是在内核中没有互斥体类型之前。

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“放弃互斥体以等待条件变量，同时轮询多个文件描述符，直至给定超时”。

我在内核线程中使用了它来监视各种共享对象的更新，并同时与内核套接字通信。

看看这个：

/**
 * 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);

结构数组kcond_poll_t是你必须自己创建和填充的东西，结构看起来像这样。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;