If the subprocess does not call the system call, will the signal sent by kill still take effect?

Question

If the subprocess does not call the system call, will the signal sent by kill still take effect?

It worked. But I want to know when did the subprocess enter the kernel mode. Code as follows.

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

int main(int argc, char const *argv[])
{
    int pid;
    if ((pid = fork()) == 0)
    {
        while (1)
            continue;
        exit(0);
    }

    sleep(3);
    kill(pid, SIGINT);

    int wid, status;
    while ((wid = wait(&status)) != -1)
    {
        printf("child %d: exited with ", wid);
        if (WIFEXITED(status))
            printf("%d\n", WEXITSTATUS(status));
        if (WIFSIGNALED(status))
            printf("%d\n", WTERMSIG(status));
    }
    return 0;
}

Answer 1

Yes, processes that do not make system calls can still receive signals. You can easily test this by writing an infinite loop program, running it, then pressing Ctrl-C, or using the kill command from another terminal window.