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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 8250f2777afc
children e542fd46ad6f
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# unlocked-io.m4 serial 15

# Copyright (C) 1998-2006, 2009-2012 Free Software Foundation, Inc.
#
# This file is free software; the Free Software Foundation
# gives unlimited permission to copy and/or distribute it,
# with or without modifications, as long as this notice is preserved.

dnl From Jim Meyering.
dnl
dnl See if the glibc *_unlocked I/O macros or functions are available.
dnl Use only those *_unlocked macros or functions that are declared
dnl (because some of them were declared in Solaris 2.5.1 but were removed
dnl in Solaris 2.6, whereas we want binaries built on Solaris 2.5.1 to run
dnl on Solaris 2.6).

AC_DEFUN([gl_FUNC_GLIBC_UNLOCKED_IO],
[
  AC_DEFINE([USE_UNLOCKED_IO], [1],
    [Define to 1 if you want getc etc. to use unlocked I/O if available.
     Unlocked I/O can improve performance in unithreaded apps,
     but it is not safe for multithreaded apps.])

  dnl Persuade glibc and Solaris <stdio.h> to declare
  dnl fgets_unlocked(), fputs_unlocked() etc.
  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])

  AC_CHECK_DECLS_ONCE([clearerr_unlocked])
  AC_CHECK_DECLS_ONCE([feof_unlocked])
  AC_CHECK_DECLS_ONCE([ferror_unlocked])
  AC_CHECK_DECLS_ONCE([fflush_unlocked])
  AC_CHECK_DECLS_ONCE([fgets_unlocked])
  AC_CHECK_DECLS_ONCE([fputc_unlocked])
  AC_CHECK_DECLS_ONCE([fputs_unlocked])
  AC_CHECK_DECLS_ONCE([fread_unlocked])
  AC_CHECK_DECLS_ONCE([fwrite_unlocked])
  AC_CHECK_DECLS_ONCE([getc_unlocked])
  AC_CHECK_DECLS_ONCE([getchar_unlocked])
  AC_CHECK_DECLS_ONCE([putc_unlocked])
  AC_CHECK_DECLS_ONCE([putchar_unlocked])
])