external/ibm-public/postfix/dist/src/util/sigdelay.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      sigdelay 3
   6 /* SUMMARY
   7 /*      delay/resume signal delivery
   8 /* SYNOPSIS
   9 /*      #include <sigdelay.h>
  10 /*
  11 /*      void    sigdelay()
  12 /*
  13 /*      void    sigresume()
  14 /* DESCRIPTION
  15 /*      sigdelay() delays delivery of signals. Signals that
  16 /*      arrive in the mean time will be queued.
  17 /*
  18 /*      sigresume() resumes delivery of signals. Signals that have
  19 /*      arrived in the mean time will be delivered.
  20 /* DIAGNOSTICS
  21 /*      All errors are fatal.
  22 /* BUGS
  23 /*      The signal queue may be really short (as in: one per signal type).
  24 /*
  25 /*      Some signals such as SIGKILL cannot be blocked.
  26 /* LICENSE
  27 /* .ad
  28 /* .fi
  29 /*      The Secure Mailer license must be distributed with this software.
  30 /* AUTHOR(S)
  31 /*      Wietse Venema
  32 /*      IBM T.J. Watson Research
  33 /*      P.O. Box 704
  34 /*      Yorktown Heights, NY 10598, USA
  35 /*--*/
  36
  37 /* System library. */
  38
  39 #include <sys_defs.h>
  40 #include <signal.h>
  41
  42 /* Utility library. */
  43
  44 #include "msg.h"
  45 #include "posix_signals.h"
  46 #include "sigdelay.h"
  47
  48 /* Application-specific. */
  49
  50 static sigset_t saved_sigmask;
  51 static sigset_t block_sigmask;
  52 static int suspending;
  53 static int siginit_done;
  54
  55 /* siginit - compute signal mask only once */
  56
  57 static void siginit(void)
  58 {
  59     int     sig;
  60
  61     siginit_done = 1;
  62     sigemptyset(&block_sigmask);
  63     for (sig = 1; sig < NSIG; sig++)
  64         sigaddset(&block_sigmask, sig);
  65 }
  66
  67 /* sigresume - deliver delayed signals and disable signal delay */
  68
  69 void    sigresume(void)
  70 {
  71     if (suspending != 0) {
  72         suspending = 0;
  73         if (sigprocmask(SIG_SETMASK, &saved_sigmask, (sigset_t *) 0) < 0)
  74             msg_fatal("sigresume: sigprocmask: %m");
  75     }
  76 }
  77
  78 /* sigdelay - save signal mask and block all signals */
  79
  80 void    sigdelay(void)
  81 {
  82     if (siginit_done == 0)
  83         siginit();
  84     if (suspending == 0) {
  85         suspending = 1;
  86         if (sigprocmask(SIG_BLOCK, &block_sigmask, &saved_sigmask) < 0)
  87             msg_fatal("sigdelay: sigprocmask: %m");
  88     }
  89 }
  90
  91 #ifdef TEST
  92
  93  /*
  94   * Test program - press Ctrl-C twice while signal delivery is delayed, and
  95   * see how many signals are delivered when signal delivery is resumed.
  96   */
  97
  98 #include <stdio.h>
  99 #include <unistd.h>
 100 #include <stdlib.h>
 101
 102 static void gotsig(int sig)
 103 {
 104     printf("Got signal %d\n", sig);
 105 }
 106
 107 int     main(int unused_argc, char **unused_argv)
 108 {
 109     signal(SIGINT, gotsig);
 110     signal(SIGQUIT, gotsig);
 111
 112     printf("Delaying signal delivery\n");
 113     sigdelay();
 114     sleep(5);
 115     printf("Resuming signal delivery\n");
 116     sigresume();
 117     exit(0);
 118 }
 119
 120 #endif