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 <linux/config.h>
  16 #include <asm/semaphore.h>
  17
  18 /*
  19  * The semaphore operations have a special calling sequence that
  20  * allow us to do a simpler in-line version of them. These routines
  21  * need to convert that sequence back into the C sequence when
  22  * there is contention on the semaphore.
  23  *
  24  * %eax contains the semaphore pointer on entry. Save the C-clobbered
  25  * registers (%eax, %edx and %ecx) except %eax whish is either a return
  26  * value or just clobbered..
  27  */
  28 asm(
  29 ".section .sched.text\n"
  30 ".align 4\n"
  31 ".globl __down_failed\n"
  32 "__down_failed:\n\t"
  33 #if defined(CONFIG_FRAME_POINTER)
  34         "pushl %ebp\n\t"
  35         "movl  %esp,%ebp\n\t"
  36 #endif
  37         "pushl %edx\n\t"
  38         "pushl %ecx\n\t"
  39         "call __down\n\t"
  40         "popl %ecx\n\t"
  41         "popl %edx\n\t"
  42 #if defined(CONFIG_FRAME_POINTER)
  43         "movl %ebp,%esp\n\t"
  44         "popl %ebp\n\t"
  45 #endif
  46         "ret"
  47 );
  48
  49 asm(
  50 ".section .sched.text\n"
  51 ".align 4\n"
  52 ".globl __down_failed_interruptible\n"
  53 "__down_failed_interruptible:\n\t"
  54 #if defined(CONFIG_FRAME_POINTER)
  55         "pushl %ebp\n\t"
  56         "movl  %esp,%ebp\n\t"
  57 #endif
  58         "pushl %edx\n\t"
  59         "pushl %ecx\n\t"
  60         "call __down_interruptible\n\t"
  61         "popl %ecx\n\t"
  62         "popl %edx\n\t"
  63 #if defined(CONFIG_FRAME_POINTER)
  64         "movl %ebp,%esp\n\t"
  65         "popl %ebp\n\t"
  66 #endif
  67         "ret"
  68 );
  69
  70 asm(
  71 ".section .sched.text\n"
  72 ".align 4\n"
  73 ".globl __down_failed_trylock\n"
  74 "__down_failed_trylock:\n\t"
  75 #if defined(CONFIG_FRAME_POINTER)
  76         "pushl %ebp\n\t"
  77         "movl  %esp,%ebp\n\t"
  78 #endif
  79         "pushl %edx\n\t"
  80         "pushl %ecx\n\t"
  81         "call __down_trylock\n\t"
  82         "popl %ecx\n\t"
  83         "popl %edx\n\t"
  84 #if defined(CONFIG_FRAME_POINTER)
  85         "movl %ebp,%esp\n\t"
  86         "popl %ebp\n\t"
  87 #endif
  88         "ret"
  89 );
  90
  91 asm(
  92 ".section .sched.text\n"
  93 ".align 4\n"
  94 ".globl __up_wakeup\n"
  95 "__up_wakeup:\n\t"
  96         "pushl %edx\n\t"
  97         "pushl %ecx\n\t"
  98         "call __up\n\t"
  99         "popl %ecx\n\t"
 100         "popl %edx\n\t"
 101         "ret"
 102 );
 103
 104 /*
 105  * rw spinlock fallbacks
 106  */
 107 #if defined(CONFIG_SMP)
 108 asm(
 109 ".section .sched.text\n"
 110 ".align 4\n"
 111 ".globl __write_lock_failed\n"
 112 "__write_lock_failed:\n\t"
 113         LOCK_PREFIX "addl       $" RW_LOCK_BIAS_STR ",(%eax)\n"
 114 "1:     rep; nop\n\t"
 115         "cmpl   $" RW_LOCK_BIAS_STR ",(%eax)\n\t"
 116         "jne    1b\n\t"
 117         LOCK_PREFIX "subl       $" RW_LOCK_BIAS_STR ",(%eax)\n\t"
 118         "jnz    __write_lock_failed\n\t"
 119         "ret"
 120 );
 121
 122 asm(
 123 ".section .sched.text\n"
 124 ".align 4\n"
 125 ".globl __read_lock_failed\n"
 126 "__read_lock_failed:\n\t"
 127         LOCK_PREFIX "incl       (%eax)\n"
 128 "1:     rep; nop\n\t"
 129         "cmpl   $1,(%eax)\n\t"
 130         "js     1b\n\t"
 131         LOCK_PREFIX "decl       (%eax)\n\t"
 132         "js     __read_lock_failed\n\t"
 133         "ret"
 134 );
 135 #endif