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

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      timed_wait 3
   6 /* SUMMARY
   7 /*      wait operations with timeout
   8 /* SYNOPSIS
   9 /*      #include <timed_wait.h>
  10 /*
  11 /*      int     timed_waitpid(pid, statusp, options, time_limit)
  12 /*      pid_t   pid;
  13 /*      WAIT_STATUS_T *statusp;
  14 /*      int     options;
  15 /*      int     time_limit;
  16 /* DESCRIPTION
  17 /*      \fItimed_waitpid\fR() waits at most \fItime_limit\fR seconds
  18 /*      for process termination.
  19 /*
  20 /*      Arguments:
  21 /* .IP "pid, statusp, options"
  22 /*      The process ID, status pointer and options passed to waitpid(3).
  23 /* .IP time_limit
  24 /*      The time in seconds that timed_waitpid() will wait.
  25 /*      This must be a number > 0.
  26 /* DIAGNOSTICS
  27 /*      Panic: interface violation.
  28 /*
  29 /*      When the time limit is exceeded, the result is -1 and errno
  30 /*      is set to ETIMEDOUT. Otherwise, the result value is the result
  31 /*      from the underlying waitpid() routine.
  32 /* BUGS
  33 /*      If there were a \fIportable\fR way to select() on process status
  34 /*      information, these routines would not have to use a steenkeeng
  35 /*      alarm() timer and signal() handler.
  36 /* LICENSE
  37 /* .ad
  38 /* .fi
  39 /*      The Secure Mailer license must be distributed with this software.
  40 /* AUTHOR(S)
  41 /*      Wietse Venema
  42 /*      IBM T.J. Watson Research
  43 /*      P.O. Box 704
  44 /*      Yorktown Heights, NY 10598, USA
  45 /*--*/
  46
  47 /* System library. */
  48
  49 #include <sys_defs.h>
  50 #include <sys/wait.h>
  51 #include <unistd.h>
  52 #include <signal.h>
  53 #include <errno.h>
  54
  55 /* Utility library. */
  56
  57 #include <msg.h>
  58 #include <posix_signals.h>
  59 #include <timed_wait.h>
  60
  61 /* Application-specific. */
  62
  63 static int timed_wait_expired;
  64
  65 /* timed_wait_alarm - timeout handler */
  66
  67 static void timed_wait_alarm(int unused_sig)
  68 {
  69
  70     /*
  71      * WARNING WARNING WARNING.
  72      *
  73      * This code runs at unpredictable moments, as a signal handler. This code
  74      * is here only so that we can break out of waitpid(). Don't put any code
  75      * here other than for setting a global flag.
  76      */
  77     timed_wait_expired = 1;
  78 }
  79
  80 /* timed_waitpid - waitpid with time limit */
  81
  82 int     timed_waitpid(pid_t pid, WAIT_STATUS_T *statusp, int options,
  83                               int time_limit)
  84 {
  85     const char *myname = "timed_waitpid";
  86     struct sigaction action;
  87     struct sigaction old_action;
  88     int     time_left;
  89     int     wpid;
  90
  91     /*
  92      * Sanity checks.
  93      */
  94     if (time_limit <= 0)
  95         msg_panic("%s: bad time limit: %d", myname, time_limit);
  96
  97     /*
  98      * Set up a timer.
  99      */
 100     sigemptyset(&action.sa_mask);
 101     action.sa_flags = 0;
 102     action.sa_handler = timed_wait_alarm;
 103     if (sigaction(SIGALRM, &action, &old_action) < 0)
 104         msg_fatal("%s: sigaction(SIGALRM): %m", myname);
 105     timed_wait_expired = 0;
 106     time_left = alarm(time_limit);
 107
 108     /*
 109      * Wait for only a limited amount of time.
 110      */
 111     if ((wpid = waitpid(pid, statusp, options)) < 0 && timed_wait_expired)
 112         errno = ETIMEDOUT;
 113
 114     /*
 115      * Cleanup.
 116      */
 117     alarm(0);
 118     if (sigaction(SIGALRM, &old_action, (struct sigaction *) 0) < 0)
 119         msg_fatal("%s: sigaction(SIGALRM): %m", myname);
 120     if (time_left)
 121         alarm(time_left);
 122
 123     return (wpid);
 124 }