Question

了解信号，我想知道过程信号掩码，阻塞信号集，信号处理程序和阻塞信号之间的细微差别。

问题涉及（在Debian上）：

sigprocmask（2）
sigsetops（3）相关功能

每个进程都有自己的信号掩码（包含被阻塞信号的长整数）。并且可以通过使用* set变量的NULL参数调用sigprocmask（2）来获得信号集，这将导致旧的进程掩码被放入* oldset，不变：

#include <string.h>
#include <signal.h>

void show_signals(const sigset_t exmask)
{

    int exsignals[43];

    exsignals[0] = SIGABRT;
    exsignals[1] = SIGALRM;
    exsignals[2] = SIGBUS;
    exsignals[3] = SIGCHLD;
    exsignals[4] = SIGCONT;
#ifdef SIGEMT
    exsignals[5] = SIGEMT;
#else
    exsignals[5] = -1;
#endif

    exsignals[6] = SIGFPE;

#ifdef SIGFREEZE
    exsignals[7] = SIGFREEZE;
#else
    exsignals[7] = -1;
#endif

    exsignals[8] = SIGHUP;
    exsignals[9] = SIGILL;
#ifdef SIGINFO
    exsignals[10] = SIGINFO;
#else
    exsignals[10] = -1;
#endif

    exsignals[11] = SIGINT;
    exsignals[12] = SIGIO;
    exsignals[13] = SIGIOT;

#ifdef SIGJVM1
    exsignals[14] = SIGJVM1;
#else
    exsignals[14] = -1;
#endif
#ifdef SIGJVM2
    exsignals[15] = SIGJVM2;
#else
    exsignals[15] = -1;
#endif

    exsignals[16] = SIGKILL;
#ifdef SIGLOST
    exsignals[17] = SIGLOST;
#else
    exsignals[17] = -1;
#endif

#ifdef SIGLWP
    exsignals[18] = SIGLWP;
#else
    exsignals[18] = -1;
#endif

    exsignals[19] = SIGPIPE;
    exsignals[20] = SIGPOLL;
    exsignals[21] = SIGPROF;
    exsignals[22] = SIGPWR;
    exsignals[23] = SIGQUIT;
    exsignals[24] = SIGSEGV;
    exsignals[25] = SIGSTKFLT;
    exsignals[26] = SIGSTOP;
    exsignals[27] = SIGSYS;
    exsignals[28] = SIGTERM;
#ifdef SIGTHAW
    exsignals[29] = SIGTHAW;
#else
    exsignals[29] = -1;
#endif
#ifdef SIGTHR
    exsignals[30] = SIGTHR;
#else
    exsignals[30] = -1;
#endif
    exsignals[31] = SIGTRAP;
    exsignals[32] = SIGTSTP;
    exsignals[33] = SIGTTIN;
    exsignals[34] = SIGTTOU;
    exsignals[35] = SIGURG;
    exsignals[36] = SIGUSR1;
    exsignals[37] = SIGUSR2;
    exsignals[38] = SIGVTALRM;
#ifdef SIGWAITING
    exsignals[39] = SIGWAITING;
#else
    exsignals[39] = -1;
#endif

    exsignals[40] = SIGWINCH;
    exsignals[41] = SIGXCPU;
    exsignals[42] = SIGXFSZ;
#ifdef SIGXRES
    exsignals[43] = SIGXRES;
#else
    exsignals[43] = -1;
#endif

    int exsignals_n = 0;

    for (;exsignals_n < 43; exsignals_n++) {
        if (exsignals[exsignals_n] == -1) continue;
        static char *exsignal_name;
        exsignal_name = strsignal(exsignals[exsignals_n]);
        switch(sigismember(&exmask, exsignals[exsignals_n]))
        {
        case 0: break;
        case 1: printf("YES %s\n", exsignal_name); break;
        case -1: printf("could not obtain signal\n"); break;
        default: printf("UNEXPECTED for %s return\n", exsignal_name); break;
        }
    }
}
const sigset_t getmask(void)
{
        static sigset_t retmask;
        if ((sigprocmask(SIG_SETMASK, NULL, &retmask)) == -1)
                printf("could not obtain process signal mask\n");

        return retmask;
}

在我的程序开始时，我意识到过程信号掩码，没有阻止任何信号。然后我将信号处理程序放入程序中。

static void sig_abrt(int signo)
{
    printf("Caught SIGABRT\n");
}

int main(void)
{
    show_signals(getmask());

    signal(SIGABRT, sig_abrt);

    show_signals(getmask());

    return 0;
}

所以现在有一个SIGABRT的信号处理程序，但如果我再次调用sigprocmask（2），如上所述，SIGABRT将不在进程信号掩码中。我尝试使用sigismember（3）进行检查，但只有在调用sigaddset（3）或其他修改信号掩码的函数后才会修改过程信号掩码。

如果我用sigaddset（3）阻止SIGABRT，信号处理程序sig_abrt在SIGABRT交付时是否会收到调用？这是否意味着信号掩码影响传递的信号？有什么区别？

另外，有没有办法在不使用sigsetops（3）和sigprocmask（2）函数的情况下阻止进程中的信号？

过程信号掩码，阻塞信号集和阻塞信号之间的差异？

0 个答案: