glibc/sysdeps/unix/sysv/linux/sleep.c

/* Implementation of the POSIX sleep function using nanosleep.
   Copyright (C) 1996, 1997, 1998, 1999 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <errno.h>
#include <time.h>
#include <signal.h>
#include <unistd.h>

/* We are going to use the `nanosleep' syscall of the kernel.  But the
   kernel does not implement the sstupid SysV SIGCHLD vs. SIG_IGN
   behaviour for this syscall.  Therefore we have to emulate it here.  */
unsigned int
__sleep (unsigned int seconds)
{
  struct timespec ts = { .tv_sec = (long int) seconds, .tv_nsec = 0 };
  sigset_t set, oset;
  unsigned int result;

  /* This is not necessary but some buggy programs depend on this.  */
  if (seconds == 0)
    return 0;

  /* Linux will wake up the system call, nanosleep, when SIGCHLD
     arrives even if SIGCHLD is ignored.  We have to deal with it
     in libc.  We block SIGCHLD first.  */
  if (__sigemptyset (&set) < 0
      || __sigaddset (&set, SIGCHLD) < 0
      || __sigprocmask (SIG_BLOCK, &set, &oset))
    return -1;

  /* If SIGCHLD is already blocked, we don't have to do anything.  */
  if (!__sigismember (&oset, SIGCHLD))
    {
      int saved_errno;
      struct sigaction oact;

      if (__sigemptyset (&set) < 0 || __sigaddset (&set, SIGCHLD) < 0)
	return -1;

      /* We get the signal handler for SIGCHLD.  */
      if (__sigaction (SIGCHLD, (struct sigaction *) NULL, &oact) < 0)
	{
	  saved_errno = errno;
	  /* Restore the original signal mask.  */
	  (void) __sigprocmask (SIG_SETMASK, &oset, (sigset_t *) NULL);
	  __set_errno (saved_errno);
	  return -1;
	}

      if (oact.sa_handler == SIG_IGN)
	{
	  /* We should leave SIGCHLD blocked.  */
	  result = __nanosleep (&ts, &ts);

	  saved_errno = errno;
	  /* Restore the original signal mask.  */
	  (void) __sigprocmask (SIG_SETMASK, &oset, (sigset_t *) NULL);
	  __set_errno (saved_errno);
	}
      else
	{
	  /* We should unblock SIGCHLD.  Restore the original signal mask.  */
	  (void) __sigprocmask (SIG_SETMASK, &oset, (sigset_t *) NULL);
	  result = __nanosleep (&ts, &ts);
	}
    }
  else
    result = __nanosleep (&ts, &ts);

  if (result != 0)
    /* Round remaining time.  */
    result = (unsigned int) ts.tv_sec + (ts.tv_nsec >= 500000000L);

  return result;
}
weak_alias (__sleep, sleep)