arch/i386/kernel/semaphore.c

   1 /*
   2  * i386 semaphore implementation.
   3  *
   4  * (C) Copyright 1999 Linus Torvalds
   5  *
   6  * Portions Copyright 1999 Red Hat, Inc.
   7  *
   8  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License
  10  *      as published by the Free Software Foundation; either version
  11  *      2 of the License, or (at your option) any later version.
  12  *
  13  * rw semaphores implemented November 1999 by Benjamin LaHaise <bcrl@kvack.org>
  14  */
  15 #include <asm/semaphore.h>
  16
  17 /*
  18  * The semaphore operations have a special calling sequence that
  19  * allow us to do a simpler in-line version of them. These routines
  20  * need to convert that sequence back into the C sequence when
  21  * there is contention on the semaphore.
  22  *
  23  * %eax contains the semaphore pointer on entry. Save the C-clobbered
  24  * registers (%eax, %edx and %ecx) except %eax whish is either a return
  25  * value or just clobbered..
  26  */
  27 asm(
  28 ".section .sched.text\n"
  29 ".align 4\n"
  30 ".globl __down_failed\n"
  31 "__down_failed:\n\t"
  32 #if defined(CONFIG_FRAME_POINTER)
  33         "pushl %ebp\n\t"
  34         "movl  %esp,%ebp\n\t"
  35 #endif
  36         "pushl %edx\n\t"
  37         "pushl %ecx\n\t"
  38         "call __down\n\t"
  39         "popl %ecx\n\t"
  40         "popl %edx\n\t"
  41 #if defined(CONFIG_FRAME_POINTER)
  42         "movl %ebp,%esp\n\t"
  43         "popl %ebp\n\t"
  44 #endif
  45         "ret"
  46 );
  47
  48 asm(
  49 ".section .sched.text\n"
  50 ".align 4\n"
  51 ".globl __down_failed_interruptible\n"
  52 "__down_failed_interruptible:\n\t"
  53 #if defined(CONFIG_FRAME_POINTER)
  54         "pushl %ebp\n\t"
  55         "movl  %esp,%ebp\n\t"
  56 #endif
  57         "pushl %edx\n\t"
  58         "pushl %ecx\n\t"
  59         "call __down_interruptible\n\t"
  60         "popl %ecx\n\t"
  61         "popl %edx\n\t"
  62 #if defined(CONFIG_FRAME_POINTER)
  63         "movl %ebp,%esp\n\t"
  64         "popl %ebp\n\t"
  65 #endif
  66         "ret"
  67 );
  68
  69 asm(
  70 ".section .sched.text\n"
  71 ".align 4\n"
  72 ".globl __down_failed_trylock\n"
  73 "__down_failed_trylock:\n\t"
  74 #if defined(CONFIG_FRAME_POINTER)
  75         "pushl %ebp\n\t"
  76         "movl  %esp,%ebp\n\t"
  77 #endif
  78         "pushl %edx\n\t"
  79         "pushl %ecx\n\t"
  80         "call __down_trylock\n\t"
  81         "popl %ecx\n\t"
  82         "popl %edx\n\t"
  83 #if defined(CONFIG_FRAME_POINTER)
  84         "movl %ebp,%esp\n\t"
  85         "popl %ebp\n\t"
  86 #endif
  87         "ret"
  88 );
  89
  90 asm(
  91 ".section .sched.text\n"
  92 ".align 4\n"
  93 ".globl __up_wakeup\n"
  94 "__up_wakeup:\n\t"
  95         "pushl %edx\n\t"
  96         "pushl %ecx\n\t"
  97         "call __up\n\t"
  98         "popl %ecx\n\t"
  99         "popl %edx\n\t"
 100         "ret"
 101 );
 102
 103 /*
 104  * rw spinlock fallbacks
 105  */
 106 #if defined(CONFIG_SMP)
 107 asm(
 108 ".section .sched.text\n"
 109 ".align 4\n"
 110 ".globl __write_lock_failed\n"
 111 "__write_lock_failed:\n\t"
 112         LOCK_PREFIX "addl       $" RW_LOCK_BIAS_STR ",(%eax)\n"
 113 "1:     rep; nop\n\t"
 114         "cmpl   $" RW_LOCK_BIAS_STR ",(%eax)\n\t"
 115         "jne    1b\n\t"
 116         LOCK_PREFIX "subl       $" RW_LOCK_BIAS_STR ",(%eax)\n\t"
 117         "jnz    __write_lock_failed\n\t"
 118         "ret"
 119 );
 120
 121 asm(
 122 ".section .sched.text\n"
 123 ".align 4\n"
 124 ".globl __read_lock_failed\n"
 125 "__read_lock_failed:\n\t"
 126         LOCK_PREFIX "incl       (%eax)\n"
 127 "1:     rep; nop\n\t"
 128         "cmpl   $1,(%eax)\n\t"
 129         "js     1b\n\t"
 130         LOCK_PREFIX "decl       (%eax)\n\t"
 131         "js     __read_lock_failed\n\t"
 132         "ret"
 133 );
 134 #endif