src/mq/mq_notify.c

   1 #include <mqueue.h>
   2 #include <pthread.h>
   3 #include <errno.h>
   4 #include <sys/socket.h>
   5 #include <signal.h>
   6 #include <unistd.h>
   7 #include <semaphore.h>
   8 #include "syscall.h"
   9
  10 struct args {
  11         sem_t sem;
  12         int sock;
  13         mqd_t mqd;
  14         int err;
  15         const struct sigevent *sev;
  16 };
  17
  18 static void *start(void *p)
  19 {
  20         struct args *args = p;
  21         char buf[32];
  22         ssize_t n;
  23         int s = args->sock;
  24         void (*func)(union sigval) = args->sev->sigev_notify_function;
  25         union sigval val = args->sev->sigev_value;
  26         struct sigevent sev2;
  27         static const char zeros[32];
  28         int err;
  29
  30         sev2.sigev_notify = SIGEV_THREAD;
  31         sev2.sigev_signo = s;
  32         sev2.sigev_value.sival_ptr = (void *)&zeros;
  33
  34         args->err = err = -__syscall(SYS_mq_notify, args->mqd, &sev2);
  35         sem_post(&args->sem);
  36         if (err) return 0;
  37
  38         pthread_detach(pthread_self());
  39         n = recv(s, buf, sizeof(buf), MSG_NOSIGNAL|MSG_WAITALL);
  40         close(s);
  41         if (n==sizeof buf && buf[sizeof buf - 1] == 1)
  42                 func(val);
  43         return 0;
  44 }
  45
  46 int mq_notify(mqd_t mqd, const struct sigevent *sev)
  47 {
  48         struct args args = { .sev = sev };
  49         pthread_attr_t attr;
  50         pthread_t td;
  51         int s;
  52         int cs;
  53         sigset_t allmask, origmask;
  54
  55         if (!sev || sev->sigev_notify != SIGEV_THREAD)
  56                 return syscall(SYS_mq_notify, mqd, sev);
  57
  58         s = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, 0);
  59         if (s < 0) return -1;
  60         args.sock = s;
  61         args.mqd = mqd;
  62
  63         if (sev->sigev_notify_attributes) attr = *sev->sigev_notify_attributes;
  64         else pthread_attr_init(&attr);
  65         pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
  66         sem_init(&args.sem, 0, 0);
  67
  68         sigfillset(&allmask);
  69         pthread_sigmask(SIG_BLOCK, &allmask, &origmask);
  70         if (pthread_create(&td, &attr, start, &args)) {
  71                 __syscall(SYS_close, s);
  72                 pthread_sigmask(SIG_SETMASK, &origmask, 0);
  73                 errno = EAGAIN;
  74                 return -1;
  75         }
  76         pthread_sigmask(SIG_SETMASK, &origmask, 0);
  77
  78         pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
  79         sem_wait(&args.sem);
  80         sem_destroy(&args.sem);
  81
  82         if (args.err) {
  83                 __syscall(SYS_close, s);
  84                 pthread_join(td, 0);
  85                 pthread_setcancelstate(cs, 0);
  86                 errno = args.err;
  87                 return -1;
  88         }
  89
  90         pthread_setcancelstate(cs, 0);
  91         return 0;
  92 }