arch/x86/lib/semaphore_32.S

   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
  16 #include <linux/linkage.h>
  17 #include <asm/rwlock.h>
  18 #include <asm/alternative-asm.h>
  19 #include <asm/frame.h>
  20 #include <asm/dwarf2.h>
  21
  22 /*
  23  * The semaphore operations have a special calling sequence that
  24  * allow us to do a simpler in-line version of them. These routines
  25  * need to convert that sequence back into the C sequence when
  26  * there is contention on the semaphore.
  27  *
  28  * %eax contains the semaphore pointer on entry. Save the C-clobbered
  29  * registers (%eax, %edx and %ecx) except %eax whish is either a return
  30  * value or just clobbered..
  31  */
  32         .section .sched.text, "ax"
  33
  34 /*
  35  * rw spinlock fallbacks
  36  */
  37 #ifdef CONFIG_SMP
  38 ENTRY(__write_lock_failed)
  39         CFI_STARTPROC simple
  40         FRAME
  41 2:      LOCK_PREFIX
  42         addl    $ RW_LOCK_BIAS,(%eax)
  43 1:      rep; nop
  44         cmpl    $ RW_LOCK_BIAS,(%eax)
  45         jne     1b
  46         LOCK_PREFIX
  47         subl    $ RW_LOCK_BIAS,(%eax)
  48         jnz     2b
  49         ENDFRAME
  50         ret
  51         CFI_ENDPROC
  52         ENDPROC(__write_lock_failed)
  53
  54 ENTRY(__read_lock_failed)
  55         CFI_STARTPROC
  56         FRAME
  57 2:      LOCK_PREFIX
  58         incl    (%eax)
  59 1:      rep; nop
  60         cmpl    $1,(%eax)
  61         js      1b
  62         LOCK_PREFIX
  63         decl    (%eax)
  64         js      2b
  65         ENDFRAME
  66         ret
  67         CFI_ENDPROC
  68         ENDPROC(__read_lock_failed)
  69
  70 #endif
  71
  72 #ifdef CONFIG_RWSEM_XCHGADD_ALGORITHM
  73
  74 /* Fix up special calling conventions */
  75 ENTRY(call_rwsem_down_read_failed)
  76         CFI_STARTPROC
  77         push %ecx
  78         CFI_ADJUST_CFA_OFFSET 4
  79         CFI_REL_OFFSET ecx,0
  80         push %edx
  81         CFI_ADJUST_CFA_OFFSET 4
  82         CFI_REL_OFFSET edx,0
  83         call rwsem_down_read_failed
  84         pop %edx
  85         CFI_ADJUST_CFA_OFFSET -4
  86         pop %ecx
  87         CFI_ADJUST_CFA_OFFSET -4
  88         ret
  89         CFI_ENDPROC
  90         ENDPROC(call_rwsem_down_read_failed)
  91
  92 ENTRY(call_rwsem_down_write_failed)
  93         CFI_STARTPROC
  94         push %ecx
  95         CFI_ADJUST_CFA_OFFSET 4
  96         CFI_REL_OFFSET ecx,0
  97         calll rwsem_down_write_failed
  98         pop %ecx
  99         CFI_ADJUST_CFA_OFFSET -4
 100         ret
 101         CFI_ENDPROC
 102         ENDPROC(call_rwsem_down_write_failed)
 103
 104 ENTRY(call_rwsem_wake)
 105         CFI_STARTPROC
 106         decw %dx    /* do nothing if still outstanding active readers */
 107         jnz 1f
 108         push %ecx
 109         CFI_ADJUST_CFA_OFFSET 4
 110         CFI_REL_OFFSET ecx,0
 111         call rwsem_wake
 112         pop %ecx
 113         CFI_ADJUST_CFA_OFFSET -4
 114 1:      ret
 115         CFI_ENDPROC
 116         ENDPROC(call_rwsem_wake)
 117
 118 /* Fix up special calling conventions */
 119 ENTRY(call_rwsem_downgrade_wake)
 120         CFI_STARTPROC
 121         push %ecx
 122         CFI_ADJUST_CFA_OFFSET 4
 123         CFI_REL_OFFSET ecx,0
 124         push %edx
 125         CFI_ADJUST_CFA_OFFSET 4
 126         CFI_REL_OFFSET edx,0
 127         call rwsem_downgrade_wake
 128         pop %edx
 129         CFI_ADJUST_CFA_OFFSET -4
 130         pop %ecx
 131         CFI_ADJUST_CFA_OFFSET -4
 132         ret
 133         CFI_ENDPROC
 134         ENDPROC(call_rwsem_downgrade_wake)
 135
 136 #endif