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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 683cbe4ca79d
children e542fd46ad6f
line wrap: on
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# warn-on-use.m4 serial 5
dnl Copyright (C) 2010-2012 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_WARN_ON_USE_PREPARE(INCLUDES, NAMES)
# ---------------------------------------
# For each whitespace-separated element in the list of NAMES, define
# HAVE_RAW_DECL_name if the function has a declaration among INCLUDES
# even after being undefined as a macro.
#
# See warn-on-use.h for some hints on how to poison function names, as
# well as ideas on poisoning global variables and macros.  NAMES may
# include global variables, but remember that only functions work with
# _GL_WARN_ON_USE.  Typically, INCLUDES only needs to list a single
# header, but if the replacement header pulls in other headers because
# some systems declare functions in the wrong header, then INCLUDES
# should do likewise.
#
# It is generally safe to assume declarations for functions declared
# in the intersection of C89 and C11 (such as printf) without
# needing gl_WARN_ON_USE_PREPARE.
AC_DEFUN([gl_WARN_ON_USE_PREPARE],
[
  m4_foreach_w([gl_decl], [$2],
    [AH_TEMPLATE([HAVE_RAW_DECL_]AS_TR_CPP(m4_defn([gl_decl])),
      [Define to 1 if ]m4_defn([gl_decl])[ is declared even after
       undefining macros.])])dnl
dnl FIXME: gl_Symbol must be used unquoted until we can assume
dnl autoconf 2.64 or newer.
  for gl_func in m4_flatten([$2]); do
    AS_VAR_PUSHDEF([gl_Symbol], [gl_cv_have_raw_decl_$gl_func])dnl
    AC_CACHE_CHECK([whether $gl_func is declared without a macro],
      gl_Symbol,
      [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([$1],
[@%:@undef $gl_func
  (void) $gl_func;])],
        [AS_VAR_SET(gl_Symbol, [yes])], [AS_VAR_SET(gl_Symbol, [no])])])
    AS_VAR_IF(gl_Symbol, [yes],
      [AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_RAW_DECL_$gl_func]), [1])
       dnl shortcut - if the raw declaration exists, then set a cache
       dnl variable to allow skipping any later AC_CHECK_DECL efforts
       eval ac_cv_have_decl_$gl_func=yes])
    AS_VAR_POPDEF([gl_Symbol])dnl
  done
])