Linux可靠/不可靠信号编程实践

综合案例

    1) 创建子进程与父进程;

    2) 注册SIGINT非实时信号与SIGRTMIN实时信号,并将这两种信号添加到进程屏蔽信号组中;

    3) 注册用户自定义信号;

    4) 子进程发送5次非实时信号,发5次实时信号;

    5) 然后子进程发送SIGUSR1解除进程对SIGINT,SIGTRMIN信号的阻塞

    6) 观察实时信号与非实时信号的区别

//程序示例
void onSigAction(int signalNumber, siginfo_t *sigInfoStruct, void *)
{
    //获取接收到的数据
    int receiveNumber = sigInfoStruct->si_int;

    //如果收到的是SIGUSR1信号,则解除对SIGINT,SIGRTMIN的屏蔽
    if (signalNumber == SIGUSR1)
    {
        sigset_t unblockSet;
        sigemptyset(&unblockSet);
        sigaddset(&unblockSet,SIGINT);
        sigaddset(&unblockSet,SIGRTMIN);;
        sigprocmask(SIG_UNBLOCK,&unblockSet,NULL);

        //Value值会是乱码!
        //cout << "Receive SIGUSR1, Value = " << receiveNumber << endl;
        cout << "Unblock, Receive SIGUSR1" << endl;
    }
    else if (signalNumber == SIGINT)
    {
        cout << "Receive SIGINT, Value = " << receiveNumber << endl;
    }
    else if (signalNumber == SIGRTMIN)
    {
        cout << "Receive SIGRTMIN, Value = " << receiveNumber << endl;
    }
}

//错误退出函数
inline void err_exit(string str);

int main()
{
    struct sigaction act;
    //如果需要使得信号处理程序接收额外数据,
    //则必须将sa_flags位置为SA_SIGINFO
    act.sa_flags = SA_SIGINFO;
    sigemptyset(&act.sa_mask);
    act.sa_sigaction = onSigAction;

    //注册信号处理函数
    if (sigaction(SIGINT,&act,NULL) < 0)
        err_exit("sigaction SIGINT");
    if (sigaction(SIGRTMIN,&act,NULL) < 0)
        err_exit("sigaction SIGRTMIN");
    if (sigaction(SIGUSR1,&act,NULL) < 0)
        err_exit("sigaction SIGUSR1");

    //将信号SIGINT,SIGRTMIN信号阻塞
    sigset_t blockSet;
    sigemptyset(&blockSet);
    sigaddset(&blockSet,SIGINT);
    sigaddset(&blockSet,SIGRTMIN);
    if (sigprocmask(SIG_BLOCK,&blockSet,NULL) < 0)
        err_exit("sigprocmask error");

    pid_t pid = fork();
    if (pid == -1)
        err_exit("fork error");
    else if (pid == 0)
    {
        union sigval Value;
        Value.sival_int = 200;

        //给父进程发送五次带额外数据的非可靠信号(其实最终只接受到了一次)
        for (int i = 0; i < 5; ++i)
        {
            ++ Value.sival_int;
            if (sigqueue(getppid(),SIGINT,Value) != 0)
                err_exit("sigqueue error");
        }

        //给父进程发送五次带额外数据的可靠信号(最终接收到了五次!!!)
        Value.sival_int = 0;
        for (int i = 0; i < 5; ++i)
        {
            ++ Value.sival_int;
            if (sigqueue(getppid(),SIGRTMIN,Value) != 0)
                err_exit("sigqueue error");
        }

        //给父进程发送SIGUSR1信号,解除对SIGINT,SIGRTMIN信号的阻塞
        kill(getppid(),SIGUSR1);
    }

    while (true)
    {
        pause();
    }
}

void err_exit(string str)
{
    perror(str.c_str());
    exit(EXIT_FAILURE);
}

运行结果:

其实只是收到了一份非可靠信号SIGINT!

附-查看系统限制命令:ulimit

xiaofang@xiaofang:~$ ulimit -a
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 47131
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 47131
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited