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  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1998 Apple Computer, Inc.  All rights reserved.
  24  *
  25  * HISTORY
  26  *
  27  */
  28
  29 /*      Copyright (c) 1992 NeXT Computer, Inc.  All rights reserved.
  30  *
  31  * EventShmemLock.h -   Shared memory area locks for use between the
  32  *                      WindowServer and the Event Driver.
  33  *
  34  *
  35  * HISTORY
  36  * 29 April 1992    Mike Paquette at NeXT
  37  *      Created.
  38  *
  39  * Multiprocessor locks used within the shared memory area between the
  40  * kernel and event system.  These must work in both user and kernel mode.
  41  * The locks are defined in an include file so they get exported to the local
  42  * include file area.
  43  *
  44  * This is basically a ripoff of the spin locks under the cthreads packages.
  45  */
  46
  47 #ifndef _IOKIT_IOSHAREDLOCKIMP_H
  48 #define _IOKIT_IOSHAREDLOCKIMP_H
  49
  50 #include <architecture/i386/asm_help.h>
  51
  52 // 'Till we're building in kernel
  53 .macro DISABLE_PREEMPTION
  54 #ifdef KERNEL
  55 #endif
  56 .endmacro
  57 .macro ENABLE_PREEMPTION
  58 #ifdef KERNEL
  59 #endif
  60 .endmacro
  61
  62 /*
  63  * void
  64  * ev_lock(p)
  65  *      int *p;
  66  *
  67  * Lock the lock pointed to by p.  Spin (possibly forever) until the next
  68  * lock is available.
  69  */
  70         TEXT
  71
  72 #ifndef KERNEL
  73 LEAF(_ev_lock, 0)
  74 LEAF(_IOSpinLock, 0)
  75         push    %eax
  76         push    %ecx
  77         movl    $1, %ecx
  78         movl    12(%esp), %eax
  79 _spin:
  80         xchgl   %ecx,0(%eax)
  81         cmp     $0, %ecx
  82         jne     _spin
  83         pop     %ecx
  84         pop     %eax
  85 END(_ev_lock)
  86 #endif
  87
  88 /*
  89  * void
  90  * ev_unlock(p)
  91  *      int *p;
  92  *
  93  * Unlock the lock pointed to by p.
  94  */
  95 LEAF(_ev_unlock, 0)
  96 LEAF(_IOSpinUnlock, 0)
  97         push    %eax
  98         movl    8(%esp),%eax
  99         movl    $0,0(%eax)
 100         ENABLE_PREEMPTION()
 101         pop     %eax
 102 END(_ev_unlock)
 103
 104
 105
 106 /*
 107  * int
 108  * ev_try_lock(p)
 109  *      int *p;
 110  *
 111  * Try to lock p.  Return zero if not successful.
 112  */
 113
 114 LEAF(_ev_try_lock, 0)
 115 LEAF(_IOTrySpinLock, 0)
 116         DISABLE_PREEMPTION()
 117         movl    4(%esp), %eax
 118    lock;bts     $0, 0(%eax)
 119         jb      1f
 120         movl    $1, %eax                /* yes */
 121         ret
 122 1:
 123         ENABLE_PREEMPTION()
 124         xorl    %eax, %eax              /* no */
 125 END(_ev_try_lock)
 126
 127
 128 #endif /* ! _IOKIT_IOSHAREDLOCKIMP_H */