Linux与FIFO等待队列的同步

Question

Linux中有等待队列为FIFO的锁吗？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））…

Linux是否具有带有FIFO等待队列的锁，或者是否有简单的方法可以利用现有机制来建立锁？

Answer 1

这是创建基于pthreads原语的简单排队“票证锁”的方法。它应该给您一些想法：

#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);
}