iokit/IOKit/i386/IOSharedLockImp.h

   1 /*
   2  * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * Copyright (c) 1998 Apple Computer, Inc.  All rights reserved.
  27  *
  28  * HISTORY
  29  *
  30  */
  31
  32 /*      Copyright (c) 1992 NeXT Computer, Inc.  All rights reserved.
  33  *
  34  * EventShmemLock.h -   Shared memory area locks for use between the
  35  *                      WindowServer and the Event Driver.
  36  *
  37  *
  38  * HISTORY
  39  * 29 April 1992    Mike Paquette at NeXT
  40  *      Created.
  41  *
  42  * Multiprocessor locks used within the shared memory area between the
  43  * kernel and event system.  These must work in both user and kernel mode.
  44  * The locks are defined in an include file so they get exported to the local
  45  * include file area.
  46  *
  47  * This is basically a ripoff of the spin locks under the cthreads packages.
  48  */
  49
  50 #ifndef _IOKIT_IOSHAREDLOCKIMP_H
  51 #define _IOKIT_IOSHAREDLOCKIMP_H
  52
  53 #include <architecture/i386/asm_help.h>
  54
  55 // 'Till we're building in kernel
  56 .macro DISABLE_PREEMPTION
  57 #ifdef KERNEL
  58 #endif
  59 .endmacro
  60 .macro ENABLE_PREEMPTION
  61 #ifdef KERNEL
  62 #endif
  63 .endmacro
  64
  65 /*
  66  * void
  67  * ev_lock(p)
  68  *      int *p;
  69  *
  70  * Lock the lock pointed to by p.  Spin (possibly forever) until the next
  71  * lock is available.
  72  */
  73         TEXT
  74
  75 #ifndef KERNEL
  76 LEAF(_ev_lock, 0)
  77 LEAF(_IOSpinLock, 0)
  78         push    %eax
  79         push    %ecx
  80         movl    $1, %ecx
  81         movl    12(%esp), %eax
  82 _spin:
  83         xchgl   %ecx,0(%eax)
  84         cmp     $0, %ecx
  85         jne     _spin
  86         pop     %ecx
  87         pop     %eax
  88 END(_ev_lock)
  89 #endif
  90
  91 /*
  92  * void
  93  * ev_unlock(p)
  94  *      int *p;
  95  *
  96  * Unlock the lock pointed to by p.
  97  */
  98 LEAF(_ev_unlock, 0)
  99 LEAF(_IOSpinUnlock, 0)
 100         push    %eax
 101         movl    8(%esp),%eax
 102         movl    $0,0(%eax)
 103         ENABLE_PREEMPTION()
 104         pop     %eax
 105 END(_ev_unlock)
 106
 107
 108
 109 /*
 110  * int
 111  * ev_try_lock(p)
 112  *      int *p;
 113  *
 114  * Try to lock p.  Return zero if not successful.
 115  */
 116
 117 LEAF(_ev_try_lock, 0)
 118 LEAF(_IOTrySpinLock, 0)
 119         DISABLE_PREEMPTION()
 120         movl    4(%esp), %eax
 121    lock;bts     $0, 0(%eax)
 122         jb      1f
 123         movl    $1, %eax                /* yes */
 124         ret
 125 1:
 126         ENABLE_PREEMPTION()
 127         xorl    %eax, %eax              /* no */
 128 END(_ev_try_lock)
 129
 130
 131 #endif /* ! _IOKIT_IOSHAREDLOCKIMP_H */