c - "STATUS: Too many open files in system"打开和锁定

Question

在Linux和C语言中，我有两个函数通过5个进程(T1，T2，...，T5)锁定16个文件(MA1，MA2，...，MA16)。使用 acquire(...) 进程-i 锁定文件(如果尚未被其他进程锁定)，将 0 写入 1，然后解锁文件。通过release(...)，进程锁定文件，将1写入0，然后解锁文件。当我使用 fork() 运行时，我从打开的 “状态:系统中打开的文件太多” 中收到以下错误。在 Linux 中，最大值为 1024，但我的 5 个进程还远未达到该限制

alessandro@LinuxAle:~$ ulimit -n
1024

代码是:

子可执行文件

#include <string.h>
#include "accessory.h"
#include "logfilemanager.h"
#include "lockmanager.h"
#include <sys/types.h>
#include <signal.h>

#define TRAIN_INITIALS "T"
#define SIZE 256

void next(int step, int *route, int size);

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

    char *name[2];
    int *route;
    int fdlog;
    char * logprint;

    memset(name, '\0', sizeof(name));
    strcpy(name, TRAIN_INITIALS);
    strcat(name, argv[1]);
    route = get_route(name, "", SIZE);
    print_route(name, route);

    fdlog = create_logfile(name, SIZE);


    for(int i = 1; i < (route[0]+1); i++)
    {
        logprint = update_logfileETC1(fdlog, i, route);
        printf("Train %s: %s", name, logprint);
        fflush(stdout);
        next(i, route, SIZE);
    }
    close(fdlog);
    return 0;
}


void next(int step, int *route, int size) {

    char * next_track_name;
    char * actual_track_name;
    char * next_file_path_name;
    char * actual_file_path_name;
    int status;
    int file_exist;

    /* acquire */
    next_track_name = get_name(route[step+1]);
    next_file_path_name = get_file_name(next_track_name, "", size);
    file_exist = access(next_file_path_name, F_OK); // check if file exist
    if(file_exist == 0)
    {
        status = acquire(next_file_path_name);
        while(status == -1)
        {
            status = acquire(next_file_path_name);
        }
    }

    sleep(3);

    /* release */
    actual_track_name = get_name(route[step]);
    actual_file_path_name = get_file_name(actual_track_name, "", size);
    file_exist = access(actual_file_path_name, F_OK); // check if file exist
    if(file_exist == 0)
    {
        status = release(actual_file_path_name);
        while(status == -1)
        {
            status = release(actual_file_path_name);
        }
    }
}

获取和释放锁定文件

include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <libgen.h>


int acquire(char *fname)
{

    char c;
    size_t nbytes;
    int status;
    int fd;
    int close_return;
    struct flock lock; //Create an variable of type struct flock to define the properties of locking

    nbytes = sizeof(c);

    fd = open(fname, O_RDWR, (mode_t)777);
    if (fd == -1)
    {
        //fd = open(fname, O_RDWR);
        printf("acquire file: %s\n", fname);
        fflush(stdout);
        perror("STATUS");
        exit(1);
    }


    memset(&lock, 0, sizeof(lock));
    lock.l_type = F_WRLCK;
    lock.l_pid = getpid();

    read(fd, &c, nbytes);

    if((c - '0') == 1){
        return -1;
    }

    /* lock the file */
    status = fcntl(fd, F_SETLK, &lock);
    if(status == -1)
    {
        return -1;
    }

    lseek(fd, 0L, SEEK_SET);
    read(fd, &c, nbytes);

    if((c - '0') == 0)
    {
        lseek(fd, 0L, SEEK_SET);
        write(fd, "1", nbytes);
    }
    else if ((c - '0') == 1)
    {
        printf("Resource %s is already acquired\n", fname);
        lock.l_type = F_ULOCK;
        if (fcntl(fd, F_SETLKW, &lock) == -1 ) {
            perror("fcntl caused some error: ");
            exit(1);
        }
    }

    /* Release the lock */
    lock.l_type = F_ULOCK;
    if (fcntl(fd, F_SETLKW, &lock) == -1 ) {
        perror("fcntl caused some error: ");
        exit(1);
    }

    if((close_return = close(fd)) < 0)
    {
        perror("close");
        exit(1);
    }

    return 0;
}



int release(char *fname)
{
    char c;
    size_t nbytes;
    int status;
    int fd;
    int close_return;
    struct flock lock; //Create an variable of type struct flock to define the properties of locking

    nbytes = sizeof(c);

    fd = open(fname, O_RDWR, (mode_t)777);
    if (fd == -1)
    {
        //fd = open(fname, O_RDWR);
        printf("release file: %s\n", fname);
        fflush(stdout);
        perror("STATUS");
        exit(1);
    }

    memset(&lock, 0, sizeof(lock));
    lock.l_type = F_WRLCK;
    lock.l_pid = getpid();

    /* lock the file */
    status = fcntl(fd, F_SETLK, &lock);
    if(status == -1)
    {
        return -1;
    }

    lseek(fd, 0L, SEEK_SET);
    write(fd, "0", nbytes);

    /* Release the lock */
    lock.l_type = F_ULOCK;
    if (fcntl(fd, F_SETLKW, &lock) == -1 ) {
        perror("fcntl caused some error: ");
        exit(EXIT_FAILURE);
    }

    if((close_return = close(fd)) < 0)
    {
        perror("close");
        exit(1);
    }

    return 0;
}

fork 的主要内容是:

#include <stdio.h>
#include <signal.h>
#include <sys/wait.h>
#include "accessory.h"
#include <sys/types.h>
#include <signal.h>


#define NUMBER_TRACKS 16
#define NUMBER_STATIONS 8
#define NUMBER_TRAINS 5

#define TRACKS_INITIALS "MA"
#define STATION_INITIALS "S"
#define SIZE 256
#define CHILDETCONE "childETCone"




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

    pid_t pid;

    char track_name[2];
    char track_number[2];
    int execl_return;

    char index[2];
    char * execl_path_name;



    /* create the MAx file initialized to zero */
    for(int i = 1; i < (NUMBER_TRACKS+1); i++)
    {
        memset(track_name, '\0', sizeof(track_name));
        memset(track_number, '\0', sizeof(track_number));
        strcpy(track_name, TRACKS_INITIALS);
        sprintf(track_number, "%d", i);
        strcat(track_name, track_number);
        create_track_file(track_name, "", SIZE);
    }

    execl_path_name = get_file_name(CHILDETCONE, "", SIZE);
    printf("path %p\n", execl_path_name);


    for(int i = 0; i < NUMBER_TRAINS; i++)
    {
        pid = fork();

        if (pid < 0)
        {
            perror("fork");
            exit(1);
        }
        if (pid == 0) //child
        {

            sprintf(index, "%d", i+1);
            execl_return = execl(execl_path_name, CHILDETCONE, index, NULL);
            if(execl_return == -1)
            {
                perror("execl");
                exit(1);
            }
            exit(0);
        }

    }

    for (int i = 0; i < NUMBER_TRAINS; i++)
    {
        wait(NULL);
    }

    return 0;

结果是:

Route of train T5: [S5, MA4, MA3, MA2, MA1, S1]
Train T5: [Attuale: S5], [Next: MA4], 7 Agosto 2018 0:35:31
Route of train T4: [S6, MA8, MA3, MA2, MA1, S1]
Train T4: [Attuale: S6], [Next: MA8], 7 Agosto 2018 0:35:31
Route of train T3: [S4, MA14, MA15, MA16, MA12, S8]
Train T3: [Attuale: S4], [Next: MA14], 7 Agosto 2018 0:35:31
Route of train T2: [S3, MA9, MA10, MA11, MA12, S8]
Train T2: [Attuale: S3], [Next: MA9], 7 Agosto 2018 0:35:31
Route of train T1: [S2, MA5, MA6, MA7, MA3, MA8, S6]
Train T1: [Attuale: S2], [Next: MA5], 7 Agosto 2018 0:35:31
Train T4: [Attuale: MA8], [Next: MA3], 7 Agosto 2018 0:35:34
Train T5: [Attuale: MA4], [Next: MA3], 7 Agosto 2018 0:35:34
Train T3: [Attuale: MA14], [Next: MA15], 7 Agosto 2018 0:35:34
Train T2: [Attuale: MA9], [Next: MA10], 7 Agosto 2018 0:35:34
Train T1: [Attuale: MA5], [Next: MA6], 7 Agosto 2018 0:35:34
acquire file: /home/alessandro/CLionProjects/ETC1/cmake-build-debug/MA3
STATUS: Too many open files in system
Train T2: [Attuale: MA10], [Next: MA11], 7 Agosto 2018 0:35:37
Train T1: [Attuale: MA6], [Next: MA7], 7 Agosto 2018 0:35:37
Train T4: [Attuale: MA3], [Next: MA2], 7 Agosto 2018 0:35:37
Train T3: [Attuale: MA15], [Next: MA16], 7 Agosto 2018 0:35:37
Train T3: [Attuale: MA16], [Next: MA12], 7 Agosto 2018 0:35:40
Train T4: [Attuale: MA2], [Next: MA1], 7 Agosto 2018 0:35:40
Train T2: [Attuale: MA11], [Next: MA12], 7 Agosto 2018 0:35:40
Train T1: [Attuale: MA7], [Next: MA3], 7 Agosto 2018 0:35:40
acquire file: /home/alessandro/CLionProjects/ETC1/cmake-build-debug/MA12
STATUS: Too many open files in system
Train T3: [Attuale: MA12], [Next: S8], 7 Agosto 2018 0:35:43
Train T4: [Attuale: MA1], [Next: S1], 7 Agosto 2018 0:35:43
Train T1: [Attuale: MA3], [Next: MA8], 7 Agosto 2018 0:35:43
Train T3: [Attuale: S8], [Next: --], 7 Agosto 2018 0:35:46
Train T4: [Attuale: S1], [Next: --], 7 Agosto 2018 0:35:46
Train T1: [Attuale: MA8], [Next: S6], 7 Agosto 2018 0:35:46
Train T1: [Attuale: S6], [Next: --], 7 Agosto 2018 0:35:49

Process finished with exit code 0

Answer 1

在获取中，您需要:

if((c - '0') == 1){
    return -1;
}

/* lock the file */
status = fcntl(fd, F_SETLK, &lock);
if(status == -1)
{
    return -1;
}

如果这些 if 语句中的任何一个返回，您将从函数中返回，而不会关闭打开的文件描述符。

注意:因为您没有发布整个子程序代码(即 execle 的目标)，所以很难确定这会产生什么效果，但其嫌疑很大。

<小时/>

更新:

I diposted the child code

好吧，这清楚地证实了错误。如果其中一个返回，acquire 和 release 都会在 next 的循环中调用-1:

1. 这意味着您将在每次后续调用中开始使用文件描述符。
2. 您可能会遇到[接近]无限循环，因为如果 next 收到 -1 返回值，它会再次[再次]调用它们

只需添加:

close(fd);

在上面的 return -1 语句之前。

请注意，release 也有类似的 if (status == -1) return -1 问题。