为什么关闭此应用程序?

处理信号是否会使应用程序关闭?我的目标是在时间用完但陷入循环时执行一些操作,直到找到用户输入q或EOF,但由于某种原因,一旦收到信号,应用程序似乎根本不执行循环,只打印printf(“从main返回!!\n”);并退出应用程序。我做错了什么?我该怎么解决?

以下是完整的代码:

#include <signal.h>
#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <ucontext.h>
#include <unistd.h>

void thread_signal_handler(int signal)
{
    // Thread's time slice has run out, switch to another thread
    // ...
    printf("time run out!!!\n");
}

int main()
{
    // Set up the signal handler for the thread's time slice
    struct sigaction sa;
    sa.sa_handler = thread_signal_handler;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sigaction(SIGALRM, &sa, NULL);

    // Set up the timer for the thread's time slice
    struct itimerval timer;
    timer.it_value.tv_sec = 5;
    timer.it_value.tv_usec = 0;
    timer.it_interval.tv_sec = 0;
    timer.it_interval.tv_usec = 0;
    setitimer(ITIMER_REAL, &timer, NULL);

    while (1)
    {
        int ch = getchar();
        if(ch == 'q' || ch == EOF) break;
    }
    printf("returning from main!!\n");
    return 0;
}