执行后无法捕获信号

Question

我试图让程序在收到信号后自行重新加载。我有这个代码

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>


void signal_callback_handler(int signum){

   printf("Caught signal %d\n",signum);

   execv("./test", NULL); //reexec myself
}

int main()
{
    signal(SIGINT, signal_callback_handler);


    printf("Program STARTED\n");

        while(1){
        printf("Program processing stuff here.\n");
        sleep(1);
    }
   return EXIT_SUCCESS;
}

问题是在 exec 程序之后只是忽略信号而不是调用信号处理程序。输出:

Program STARTED
Program processing stuff here.
Program processing stuff here.
^CCaught signal 2
Program STARTED
Program processing stuff here.
^C^CProgram processing stuff here. 
^C^C^C^C^CProgram processing stuff here. 
^C^CProgram processing stuff here.

如何使信号处理程序在 exec 之后工作？

Answer 1

信号掩码在 exec 中继承，并且 SIGINT 在调用信号处理程序期间被阻止，这会调用 execve。因此，您重新执行的图像是在 SIGINT 被阻止的情况下启动的。

如果跟踪该过程，您会看到您的 signal 调用变成如下所示:

3143  rt_sigaction(SIGINT, {0xabcd, [INT], SA_RESTORER|SA_RESTART, 0xabcd}, {SIG_DFL, [], 0}, 8) = 0
                                    ^^^^^
                                      |
                                      +--- SIGINT is blocked during handler!

sigaction 会让您更好地控制信号处理程序，is recommended over signal .