core/idle.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2008 H. Peter Anvin - All Rights Reserved
   4  *   Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
   5  *
   6  *   This program is free software; you can redistribute it and/or modify
   7  *   it under the terms of the GNU General Public License as published by
   8  *   the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
   9  *   Boston MA 02110-1301, USA; either version 2 of the License, or
  10  *   (at your option) any later version; incorporated herein by reference.
  11  *
  12  * ----------------------------------------------------------------------- */
  13
  14 /*
  15  * idle.c:
  16  *
  17  * This function provided protected-mode access to the idle handling.
  18  * It needs to be carefully coordinated with idle.inc, which provides
  19  * idle services to real-mode code.
  20  */
  21
  22 #include "core.h"
  23 #include <x86/cpu.h>
  24
  25 #define TICKS_TO_IDLE   4       /* Also in idle.inc */
  26
  27 static jiffies_t _IdleTimer;
  28 __export uint16_t NoHalt = 0;
  29
  30 int (*idle_hook_func)(void);
  31
  32 void reset_idle(void)
  33 {
  34     _IdleTimer = jiffies();
  35     sti();      /* Guard against BIOS/PXE brokenness... */
  36 }
  37
  38 __export void __idle(void)
  39 {
  40     if (jiffies() - _IdleTimer < TICKS_TO_IDLE)
  41         return;
  42
  43     if (idle_hook_func && idle_hook_func())
  44         return;                 /* Nonzero return = do not idle */
  45
  46     sti();
  47     if (NoHalt)
  48         cpu_relax();
  49     else
  50         hlt();
  51 }