Linux与FIFO等待队列的同步

问题描述：

在等待队列为FIFO的Linux中是否有锁?这似乎是一件显而易见的事情，但是我刚刚发现pthread互斥锁不是FIFO，信号量显然也不是FIFO(我正在研究内核2.4(家庭作业))...

Are there locks in Linux where the waiting queue is FIFO? This seems like such an obvious thing, and yet I just discovered that pthread mutexes aren't FIFO, and semaphores apparently aren't FIFO either (I'm working on kernel 2.4 (homework))...

Linux是否具有带有FIFO等待队列的锁，还是有一种简单的方法来利用现有机制进行锁定?

Does Linux have a lock with FIFO waiting queue, or is there an easy way to make one with existing mechanisms?

答

这里是一种创建基于pthreads原语的简单队列票证锁"的方法.它应该给您一些想法:

Here is a way to create a simple queueing "ticket lock", built on pthreads primitives. It should give you some ideas:

#include <pthread.h>

typedef struct ticket_lock {
    pthread_cond_t cond;
    pthread_mutex_t mutex;
    unsigned long queue_head, queue_tail;
} ticket_lock_t;

#define TICKET_LOCK_INITIALIZER { PTHREAD_COND_INITIALIZER, PTHREAD_MUTEX_INITIALIZER }

void ticket_lock(ticket_lock_t *ticket)
{
    unsigned long queue_me;

    pthread_mutex_lock(&ticket->mutex);
    queue_me = ticket->queue_tail++;
    while (queue_me != ticket->queue_head)
    {
        pthread_cond_wait(&ticket->cond, &ticket->mutex);
    }
    pthread_mutex_unlock(&ticket->mutex);
}

void ticket_unlock(ticket_lock_t *ticket)
{
    pthread_mutex_lock(&ticket->mutex);
    ticket->queue_head++;
    pthread_cond_broadcast(&ticket->cond);
    pthread_mutex_unlock(&ticket->mutex);
}

Linux与FIFO等待队列的同步

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