如何在读写器问题中检测饥饿

Question

我对这段代码有疑问。这是经典的读者-作家问题。我遵循了在该维基百科页面上找到的伪代码，以解决第一个使作家感到饥饿的问题。我想知道我实际上如何注意到作家们正在挨饿。

我试图在不同地方放置shared_variable的打印语句，但这并没有给我带来太多的见识。但是也许我只是不明白发生了什么。有人可以向我解释如何从视觉上看到饥饿的发生吗？谢谢！读者或作者尝试读取或写入的尝试次数以命令行参数的形式给出。

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <semaphore.h>
#include <pthread.h>


// Compile it like so: gcc assignment2.c -lpthread


// Shared variables (semaphore and integer)
static sem_t rw_mutex;
static sem_t mutex;
static int read_count = 0;

// Shared variable
int shared_variable = 0;

static void *writerAction(void *arg)
    int number_attempt = *((int *) arg);
    int attempt = 0;
    do
        sem_wait(&rw_mutex);
        shared_variable = shared_variable + 10;
        sem_post(&rw_mutex);
        attempt++;
    while(attempt < number_attempt);


static void *readerAction(void *arg)
    int number_attempt = *((int *) arg);
    int attempt = 0;
   do
        sem_wait(&mutex);
        read_count++;
        // waiting to be able to read for the possible writer
        if (read_count == 1 )
            sem_wait(&rw_mutex); // get the lock so that writter can't write!
        

        // Release the read_count variable
        sem_post(&mutex);
        sem_wait(&mutex);
        read_count--;

        if (read_count == 0)
            sem_post(&rw_mutex); // release the lock so that writter can write
        
        sem_post(&mutex);
        attempt++;
     while(attempt < number_attempt);





int main(int argc, char *argv[]) 

    int number_writers = 10;
    int number_readers = 500;
    int reader_repeat_count = atoi(argv[2]);
    int writer_repeat_count = atoi(argv[1]);

    // Instantiating the threads for the writters and readers
    pthread_t writer_threads[number_writers];
    pthread_t reader_threads[number_readers];

    // Initation of semaphores
    sem_init(&rw_mutex, 0, 1);
    sem_init(&mutex, 0, 1);

    printf("Start creation of Readers\n");
    for(int i = 0; i <number_readers; i++)
        pthread_create(&reader_threads[i], NULL, readerAction, &reader_repeat_count);
    
    printf("Start creation of Writers\n");
    for(int i = 0; i < number_writers; i++)
        pthread_create(&writer_threads[i], NULL, writerAction, &writer_repeat_count);
    

    // All the actions is hapenning here
    printf("Wait for Readers\n");
    for(int i = 0; i < number_readers; i++)
        printf("Waiting for : %d\n",i);
        pthread_join(reader_threads[i], NULL);
    

    printf("Wait for Writers\n");
    // Collect all the writers
    for(int i = 0; i < number_writers; i++)
        printf("Waiting for : %d\n",i);
        pthread_join(writer_threads[i], NULL);
    

    // Results
    printf("The shared variable is : %d\n",shared_variable);