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sigaction将SIGINT传递给系统调用,但不传递信号

signals sockets c

ollien · 技术社区 · 6 年前

我有一个循环处理一个 accept(2) 打电话。我想在一个 SIGINT signal 功能。

void signal_handler(int signal) {
    printf("Caught signal\n");
}

int main() {
    signal(SIGINT, &signal_handler);
    // ...
    int accept_fd = accept(sock, NULL, NULL);
    if (accept_fd == -1) {
        close(sock);
        perror("accept");
        return 1;
    }
    // ...
}

如果我修改 main 使用 sigaction

int main() {
    struct sigaction sa;
    sa.sa_handler = &signal_handler;
    sa.sa_flags = 0;
    sigemptyset(&sa.sa_mask);
    sigaction(SIGINT, &sa, NULL);
    // ...
    int accept_fd = accept(sock, NULL, NULL);
    if (accept_fd == -1) {
        close(sock);
        perror("accept");
        return 1;
    }
    // ...
}

发送信号后,我得到 Caught Signal ,后跟 accept: Interrupted system call . 从手册页 接受(2)

错误

EINTR系统调用被在有效连接到达之前捕获的信号中断;请参阅信号(7)。

我明白更现代,我应该多用一次 信号 ,但我很好奇为什么它提供了这种功能上的差异。

下面我为每个案例提供了一个完整的可用示例程序。

信号示例(2)

#include <netdb.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>

#define BUFFER_SIZE 32

void signal_handler(int signal) {
    printf("Caught signal\n");
}

int main() {
    signal(SIGINT, &signal_handler);
    struct addrinfo hints;
    memset(&hints, 0, sizeof(struct addrinfo));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    struct addrinfo *addr_info;
    int info_result = getaddrinfo("localhost", "8080", &hints, &addr_info);
    if (info_result != 0) {
        printf("Getting address failed\n");
        return 1;
    }
    int sock = socket(addr_info->ai_family, addr_info->ai_socktype, addr_info->ai_protocol);
    if (sock == -1) {
        printf("Socket Failed\n");
        return 1;
    }
    int bind_result = bind(sock, addr_info->ai_addr, addr_info->ai_addrlen);
    if (bind_result == -1) {
        close(sock);
        printf("Bind Failed\n");
        return 1;
    }
    int listen_result = listen(sock, 8);
    if (listen_result == -1) {
        close(sock);
        printf("Listen Failed\n");
        return 1;
    }
    printf("Waiting...\n");
    int accept_fd = accept(sock, NULL, NULL);
    if (accept_fd == -1) {
        close(sock);
        perror("accept");
        return 1;
    }
    printf("Got fd %d\n", accept_fd);
    char *buffer = malloc(BUFFER_SIZE * sizeof(char));
    int n;
    while ((n = read(accept_fd, buffer, BUFFER_SIZE)) > 0) {
        printf("%.*s\n", n, buffer);
    }
    close(sock);
}

#include <netdb.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>

#define BUFFER_SIZE 32

void signal_handler(int signal) {
    printf("Caught signal\n");
}

int main() {
    struct sigaction sa;
    sa.sa_handler = &signal_handler;
    sa.sa_flags = 0;
    sigemptyset(&sa.sa_mask);
    sigaction(SIGINT, &sa, NULL);
    struct addrinfo hints;
    memset(&hints, 0, sizeof(struct addrinfo));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    struct addrinfo *addr_info;
    int info_result = getaddrinfo("localhost", "8080", &hints, &addr_info);
    if (info_result != 0) {
        printf("Getting address failed\n");
        return 1;
    }
    int sock = socket(addr_info->ai_family, addr_info->ai_socktype, addr_info->ai_protocol);
    if (sock == -1) {
        printf("Socket Failed\n");
        return 1;
    }
    int bind_result = bind(sock, addr_info->ai_addr, addr_info->ai_addrlen);
    if (bind_result == -1) {
        close(sock);
        printf("Bind Failed\n");
        return 1;
    }
    int listen_result = listen(sock, 8);
    if (listen_result == -1) {
        close(sock);
        printf("Listen Failed\n");
        return 1;
    }
    printf("Waiting...\n");
    int accept_fd = accept(sock, NULL, NULL);
    if (accept_fd == -1) {
        close(sock);
        perror("accept");
        return 1;
    }
    printf("Got fd %d\n", accept_fd);
    char *buffer = malloc(BUFFER_SIZE * sizeof(char));
    int n;
    while ((n = read(accept_fd, buffer, BUFFER_SIZE)) > 0) {
        printf("%.*s\n", n, buffer);
    }
    close(sock);
}

1 回复 | 直到 4 年前

John Zwinck 6 年前

在BSD和Linux上, signal() 相当于 sigaction() 具有 sa_flags 设置为 SA_RESTART . 如果你把旗子放在你的 sigaction() 代码,它的行为与 sigaction() .

来自 Linux man page

在BSD上, 当一个信号处理程序被调用时,信号的配置是不正确的在处理程序执行时传递。此外,某些阻塞系统调用在被中断时自动重新启动使用以下标志调用sigaction(2):

       sa.sa_flags = SA_RESTART;