c - 多线程 C 程序无法使用参数运行

Question

我正在用 C 编写一个程序。这是一个多线程程序，应该有一个线程(读取器)读取文件中一行上的两个 int，然后打印它们。另一个线程必须添加整数，然后打印结果。

它们只允许与信号进行通信，不允许使用互斥体、信号量或条件变量。

我遇到的问题是，当我使用 Numbers.txt 作为参数运行程序时，似乎什么也没有发生。我认为它在尝试打开文件时停止，但我不太确定。

非常感谢任何人提供的帮助，谢谢。

编辑:用strace运行它，发生了什么:http://pastebin.com/DPf6RPKf

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <pthread.h>


//Struct for numbers and file
typedef struct
{
    int num0, num1;
    FILE *fp;
    pid_t *pid;
    unsigned int seed;

} pair_t;

static void cleanExitReader()
{

    printf("Goodbye from Reader Thread");
}

static void cleanExitCalc()
{
    printf("Goodbye from Calculator Thread");
}


//Reader thread
static void *
readerThread(void *numPair_in)
{
    //Install cleanup handler
    pthread_cleanup_push(cleanExitReader, NULL);
    //Cast numPair_in as the struct
    pair_t * numPair;
    numPair = (pair_t *)numPair_in;
    unsigned int seed;
    //Create sigset and block
    sigset_t blockSigs;
    sigaddset(&blockSigs, SIGUSR1);
    sigaddset(&blockSigs, SIGUSR2);
    pthread_sigmask(SIG_BLOCK, &blockSigs, NULL);

    //Create a sigset for sigwait to listen for.
    sigset_t listenSigs;
    sigemptyset(&listenSigs);
    sigaddset(&listenSigs, SIGUSR1);
    int listenSigs_r;

    //Reading loop
    while(1)
    {
        //Wait for signal from main before starting.
        sigwait(&listenSigs, &listenSigs_r);
        if(fscanf(numPair->fp, "%d %d", &numPair->num0, &numPair->num1) == EOF)
            continue;
        usleep(rand_r(&seed) % 10000);
        printf("%d %d", numPair->num0, numPair->num1);
        kill(*numPair->pid, SIGUSR1);
    }

    pthread_cleanup_pop(1);
}


//Calculator thread
static void *
calcThread(void *numPair_in)
{
    //Install cleanup handler
    pthread_cleanup_push(cleanExitCalc, NULL);
    unsigned int seed;
    //Cast numPair_in as the struct
    pair_t * numPair;
    numPair = (pair_t *)numPair_in;

    //Create sigset and block
    sigset_t blockSigs;
    sigaddset(&blockSigs, SIGUSR1);
    sigaddset(&blockSigs, SIGUSR2);
    pthread_sigmask(SIG_BLOCK, &blockSigs, NULL);

    //Create a sigset for sigwait to wait for.
    sigset_t listenSigs;
    sigemptyset(&listenSigs);
    sigaddset(&listenSigs, SIGUSR2);
    int listenSigs_r;

    //Adding loop
    while(1)
    {
        sigwait(&listenSigs, &listenSigs_r);
        if(feof(numPair->fp))
            continue;
        int i = numPair->num0 + numPair->num1;
        usleep(rand_r(&seed) % 10000);
        printf("%d", i);
        kill(*numPair->pid, SIGUSR2);
    }

    pthread_cleanup_pop(1);
}


//Main
int main (int argc, char *argv[])
{
    //Declare threads, file pointer, pid and struct
    pthread_t r, c;
    FILE *fp;
    pid_t pid;
    pair_t numbers;

    //Exit if no argument given
    if(argc < 2)
    {
        printf("Please enter one file as an argument");
        return 1;
    }

    //Open file
    fp = fopen(argv[1], "r");

    //Exit if fp = null
    if(fp == NULL)
    {
        perror("fopen");
        return 1;
    }

    //Get the process ID of the program
    pid = getpid();

    //Assign values to struct pid and fp
    numbers.pid = &pid;
    numbers.fp = fp;


    //Blocking SIGUSR1 and SIGUSR2
    sigset_t blockSigs;
    sigaddset(&blockSigs, SIGUSR1);
    sigaddset(&blockSigs, SIGUSR2);
    pthread_sigmask(SIG_BLOCK, &blockSigs, NULL);

    //Set up the listening set for SIGUSR1/2
    sigset_t listenSigs;
    sigemptyset(&listenSigs);
    sigaddset(&listenSigs, SIGUSR1);
    sigaddset(&listenSigs, SIGUSR2);
    int listenSigs_r;

    //Create threads here so they inherit sigmasks
    pthread_create(&r, NULL, readerThread, (void *)&numbers);
    pthread_create(&c, NULL, calcThread, (void *)&numbers);

    while(1)
    {
        if(feof(fp))
            break;
        pthread_kill(r, SIGUSR1);
        sigwait(&listenSigs, &listenSigs_r);

        pthread_kill(c, SIGUSR2);
        sigwait(&listenSigs, &listenSigs_r);
    }

    pthread_cancel(r);
    pthread_cancel(c);
    pthread_join(r, NULL);
    pthread_join(c, NULL);

    fclose(fp);
    return 0;
}

Answer 1

您有两个主要问题:

(1) 混合 kill 和 pthread_kill。 kill 会将信号发送到进程，等待该信号的线程收到该信号的机会是随机的。 pthread_kill 将其定向到特定线程。因此，当读取器线程向进程发送 kill sigusr1 时，读取器和主进程都在等待它，并且读取器每次都会得到它，从而抛出序列。通过将其更改为pthread_kill，它可以被定向到正确的线程。

(2) eof 逻辑已关闭。 reader 会点击 eof 并立即循环并等待，从不通知 main 事情已经完成。

这是你的 95% 的代码，所以我不会因为把它交给你而感到内疚，但你仍然需要仔细检查它，查看更改并清理它

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <pthread.h>

//Struct for numbers and file
typedef struct
{
    int num0, num1;
    FILE *fp;
    //pid_t *pid;
    pthread_t tid;
    unsigned int seed;
} pair_t;

static void cleanExitReader()
{    
    printf("Goodbye from Reader Thread\n");
}

static void cleanExitCalc()
{
    printf("Goodbye from Calculator Thread\n");
}

//Reader thread
static void *
readerThread(void *numPair_in)
{
    //Install cleanup handler
    pthread_cleanup_push(cleanExitReader, NULL);
    //Cast numPair_in as the struct
    pair_t * numPair;
    numPair = (pair_t *)numPair_in;
    unsigned int seed;

    //Create a sigset for sigwait to listen for.
    sigset_t listenSigs;
    sigemptyset(&listenSigs);
    sigaddset(&listenSigs, SIGUSR1);
    int listenSigs_r;

     //Reading loop
    while(1)
    {
        //Wait for signal from main before starting.
        int result = sigwait(&listenSigs, &listenSigs_r);
        if(result == 0)
            printf("reader sigwait got signal: %d\n", listenSigs_r);

        if(fscanf(numPair->fp, "%d %d", &numPair->num0, &numPair->num1) == EOF)
        {
            pthread_kill(numPair->tid, SIGUSR1);
            continue;
        }
        else
        {
            //usleep(rand_r(&seed) % 10000);
            printf("read values: %d %d\n", numPair->num0, numPair->num1);
            pthread_kill(numPair->tid, SIGUSR1);
        }
    }

    pthread_cleanup_pop(1);
}


//Calculator thread
static void *
calcThread(void *numPair_in)
{
    //Install cleanup handler
    pthread_cleanup_push(cleanExitCalc, NULL);
    unsigned int seed;
    //Cast numPair_in as the struct
    pair_t * numPair;
    numPair = (pair_t *)numPair_in;

    //Create a sigset for sigwait to wait for.
    sigset_t listenSigs;
    sigemptyset(&listenSigs);
    sigaddset(&listenSigs, SIGUSR2);
    int listenSigs_r;

    //Adding loop
    while(1)
    {
        int result = sigwait(&listenSigs, &listenSigs_r);
        if(result == 0)
            printf("calc sigwait got signal: %d\n", listenSigs_r);

        int i = numPair->num0 + numPair->num1;
        //usleep(rand_r(&seed) % 10000);
        printf("result of calc = %d\n", i);
        pthread_kill(numPair->tid, SIGUSR2);
    }

    pthread_cleanup_pop(1);
}


//Main
int main (int argc, char *argv[])
{
    //Declare threads, file pointer, tid and struct
    pthread_t r, c;
    FILE *fp;
    //pid_t pid;
    pthread_t tid;
    pair_t numbers;

    //Exit if no argument given
    if(argc < 2)
    {
        printf("Please enter one file as an argument\n");
        return 1;
    }

    //Open file
    fp = fopen(argv[1], "r");

    //Exit if fp = null
    if(fp == NULL)
    {
        perror("fopen");
        return 1;
    }

    //Get the process ID of the program
    //pid = getpid();
    tid = pthread_self();

    //Assign values to struct tid and fp
    numbers.tid = tid;
    numbers.fp = fp;


    //Blocking SIGUSR1 and SIGUSR2
    sigset_t blockSigs;
    sigaddset(&blockSigs, SIGUSR1);
    sigaddset(&blockSigs, SIGUSR2);
    pthread_sigmask(SIG_BLOCK, &blockSigs, NULL);

    //Create threads here so they inherit sigmasks
    pthread_create(&r, NULL, readerThread, (void *)&numbers);
    pthread_create(&c, NULL, calcThread, (void *)&numbers);

    //Set up the listening set for SIGUSR1/2
    sigset_t listenSigs;
    sigemptyset(&listenSigs);
    sigaddset(&listenSigs, SIGUSR1);
    sigaddset(&listenSigs, SIGUSR2);
    int listenSigs_r;

    while(1)
    {
        if(feof(fp))
            break;

        pthread_kill(r, SIGUSR1);
        int result = sigwait(&listenSigs, &listenSigs_r);
        if(result == 0)
            printf("main 1 sigwait got signal: %d\n", listenSigs_r);


        pthread_kill(c, SIGUSR2);
        sigwait(&listenSigs, &listenSigs_r);
        if(result == 0)
            printf("main 2 sigwait got signal: %d\n", listenSigs_r);

        printf("\n\n"); //easier to read

    }

    pthread_cancel(r);
    pthread_cancel(c);
    pthread_join(r, NULL);
    pthread_join(c, NULL);

    fclose(fp);
    return 0;
}