view m4/pty_h.m4 @ 16869:38e6d30d7e4d

poll/select: prevent busy-waiting 2012-05-21 Paolo Bonzini <bonzini@gnu.org> poll/select: prevent busy-waiting. SwitchToThread() only gives away the rest of the current time slice to another thread in the current process. So if the thread that feeds the file decscriptor we're polling is not in the current process, we get busy-waiting. * lib/poll.c: Use SleepEx(1, TRUE) instead of SwitchToThread(). Patch from Theodore Leblond. * lib/select.c: Split polling out of the loop that sets the output fd_sets. Check for zero result and loop if the wait timeout is infinite.
author Paolo Bonzini <bonzini@gnu.org>
date Mon, 21 May 2012 09:52:42 +0200
parents 8250f2777afc
children e542fd46ad6f
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# pty_h.m4 serial 10
dnl Copyright (C) 2009-2012 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

# gl_PTY_H
# --------
# Set up the GNU-like <pty.h> replacement header.
AC_DEFUN_ONCE([gl_PTY_H],
[
  AC_REQUIRE([gl_PTY_H_DEFAULTS])

  # Make sure that pty.h provides forkpty, or setup the replacement.
  AC_CHECK_HEADERS_ONCE([pty.h])
  if test $ac_cv_header_pty_h != yes; then
    HAVE_PTY_H=0
    AC_CHECK_HEADERS([util.h libutil.h])
    if test $ac_cv_header_util_h = yes; then
      HAVE_UTIL_H=1
    fi
    if test $ac_cv_header_libutil_h = yes; then
      HAVE_LIBUTIL_H=1
    fi
  else # Have <pty.h>, assume forkpty is declared there.
    HAVE_PTY_H=1
  fi
  AC_SUBST([HAVE_PTY_H])
  dnl <pty.h> is always overridden, because of GNULIB_POSIXCHECK.
  gl_CHECK_NEXT_HEADERS([pty.h])

  dnl Check for declarations of anything we want to poison if the
  dnl corresponding gnulib module is not in use.
  gl_WARN_ON_USE_PREPARE([[
/* <sys/types.h> is a prerequisite of <libutil.h> on FreeBSD 8.0.  */
#include <sys/types.h>
#if HAVE_PTY_H
# include <pty.h>
#endif
#if HAVE_UTIL_H
# include <util.h>
#endif
#if HAVE_LIBUTIL_H
# include <libutil.h>
#endif
    ]], [forkpty openpty])
])

AC_DEFUN([gl_PTY_MODULE_INDICATOR],
[
  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
  AC_REQUIRE([gl_PTY_H_DEFAULTS])
  gl_MODULE_INDICATOR_SET_VARIABLE([$1])
  dnl Define it also as a C macro, for the benefit of the unit tests.
  gl_MODULE_INDICATOR_FOR_TESTS([$1])
])

AC_DEFUN([gl_PTY_H_DEFAULTS],
[
  GNULIB_FORKPTY=0;     AC_SUBST([GNULIB_FORKPTY])
  GNULIB_OPENPTY=0;     AC_SUBST([GNULIB_OPENPTY])
  dnl Assume proper GNU behavior unless another module says otherwise.
  HAVE_UTIL_H=0;        AC_SUBST([HAVE_UTIL_H])
  HAVE_LIBUTIL_H=0;     AC_SUBST([HAVE_LIBUTIL_H])
  HAVE_FORKPTY=1;       AC_SUBST([HAVE_FORKPTY])
  HAVE_OPENPTY=1;       AC_SUBST([HAVE_OPENPTY])
  REPLACE_FORKPTY=0;    AC_SUBST([REPLACE_FORKPTY])
  REPLACE_OPENPTY=0;    AC_SUBST([REPLACE_OPENPTY])
])