Hi,

I wonna to receive siginfo struct available in Linux for real-time signals. More specifically, I wonna recieve file descriptor number for SIG_IO events.

After diggin Perl sources I realized I can't recieve this neither in normal Perlish way thru $SIG{signo} handler nor thru POSIX sigaction. This is because Perl declare Perl_sighandler(int) but not like void (*sa_sigaction)(int, siginfo_t *, void *). So small XS was written (skeleton of this XS posted below).

Question : is this safe ? Can my signal handler ruins something ? Can any problems be if my handler fire than Perl for example runs malloc ? And the most important question : is there are any better way to retrieve siginfo in signal handler ?
Question2 : can I safe (relatevely safe :) ) make simple Perl callback in signal handler ? (of course this callback will as small as possible like Perl signal handlers before "Perl safe signals". 

//...
static int FD_set[MAX_FD], FD_q[MAX_FD];
// Static structures here to not make malloc at all :)
static int pos = 1;
static int sig;

void Handler(int sig, siginfo_t *si, void *whatisthis) {
    // work like Edge Triggered
    if (FD_set[si->si_fd]) {;
        return;
    }
    FD_set[si->si_fd] = pos;
    FD_q[pos] = si->si_fd;
    pos++;
}

MODULE = RtSig          PACKAGE = RtSig

int
SetSigaction(arg)
       int     arg
   CODE:
        struct  sigaction  act;
        sig = arg;
        act.sa_flags = SA_SIGINFO|SA_RESTART;
        act.sa_sigaction = Handler;
        sigfillset(&act.sa_mask);
        if (sigaction(sig, &act, 0) == 0) {
            RETVAL = 1;
        } else {
            XSRETURN_UNDEF;
        }
   OUTPUT:
       RETVAL

void
Poll()
   INIT:
       int i;
       sigset_t mask, old_mask;
   PPCODE:
       sigemptyset(&mask);
       sigaddset(&mask, sig);
       sigprocmask(SIG_BLOCK, &mask, &old_mask);
       for (i=1; i < pos; i++) {
           XPUSHs(sv_2mortal(newSVnv(FD_q[i])));
           FD_set[FD_q[i]] = 0;
           FD_q[i] = 0;
       }
       pos = 1;
       sigprocmask(SIG_SETMASK, &old_mask, 0);

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In reply to receive siginfo for real time signals. by asdfgroup

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