sysdeps/unix/sysv/linux/sleep.c

   1 /* Implementation of the POSIX sleep function using nanosleep.
   2    Copyright (C) 1996, 1997, 1998, 1999 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <errno.h>
  22 #include <time.h>
  23 #include <signal.h>
  24 #include <unistd.h>
  25
  26 /* We are going to use the `nanosleep' syscall of the kernel.  But the
  27    kernel does not implement the sstupid SysV SIGCHLD vs. SIG_IGN
  28    behaviour for this syscall.  Therefore we have to emulate it here.  */
  29 unsigned int
  30 __sleep (unsigned int seconds)
  31 {
  32   struct timespec ts = { tv_sec: (long int) seconds, tv_nsec: 0 };
  33   sigset_t set, oset;
  34   unsigned int result;
  35
  36   /* This is not necessary but some buggy programs depend on this.  */
  37   if (seconds == 0)
  38     return 0;
  39
  40   /* Linux will wake up the system call, nanosleep, when SIGCHLD
  41      arrives even if SIGCHLD is ignored.  We have to deal with it
  42      in libc.  We block SIGCHLD first.  */
  43   if (__sigemptyset (&set) < 0
  44       || __sigaddset (&set, SIGCHLD) < 0
  45       || __sigprocmask (SIG_BLOCK, &set, &oset))
  46     return -1;
  47
  48   /* If SIGCHLD is already blocked, we don't have to do anything.  */
  49   if (!__sigismember (&oset, SIGCHLD))
  50     {
  51       int saved_errno;
  52       struct sigaction oact;
  53
  54       if (__sigemptyset (&set) < 0 || __sigaddset (&set, SIGCHLD) < 0)
  55         return -1;
  56
  57       /* We get the signal handler for SIGCHLD.  */
  58       if (__sigaction (SIGCHLD, (struct sigaction *) NULL, &oact) < 0)
  59         {
  60           saved_errno = errno;
  61           /* Restore the original signal mask.  */
  62           (void) __sigprocmask (SIG_SETMASK, &oset, (sigset_t *) NULL);
  63           __set_errno (saved_errno);
  64           return -1;
  65         }
  66
  67       if (oact.sa_handler == SIG_IGN)
  68         {
  69           /* We should leave SIGCHLD blocked.  */
  70           result = __nanosleep (&ts, &ts);
  71
  72           saved_errno = errno;
  73           /* Restore the original signal mask.  */
  74           (void) __sigprocmask (SIG_SETMASK, &oset, (sigset_t *) NULL);
  75           __set_errno (saved_errno);
  76         }
  77       else
  78         {
  79           /* We should unblock SIGCHLD.  Restore the original signal mask.  */
  80           (void) __sigprocmask (SIG_SETMASK, &oset, (sigset_t *) NULL);
  81           result = __nanosleep (&ts, &ts);
  82         }
  83     }
  84   else
  85     result = __nanosleep (&ts, &ts);
  86
  87   if (result != 0)
  88     /* Round remaining time.  */
  89     result = (unsigned int) ts.tv_sec + (ts.tv_nsec >= 500000000L);
  90
  91   return result;
  92 }
  93 weak_alias (__sleep, sleep)