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         movl            4(%esp), %ecx
  79 0:
  80         xorl            %eax, %eax
  81         rep
  82         nop             /* pause for hyperthreaded CPU's */
  83         lock
  84         cmpxchgl        %ecx, (%ecx)
  85         jne             0b
  86         ret
  87 END(_ev_lock)
  88 #endif
  89
  90 /*
  91  * void
  92  * ev_unlock(p)
  93  *      int *p;
  94  *
  95  * Unlock the lock pointed to by p.
  96  */
  97 LEAF(_ev_unlock, 0)
  98 LEAF(_IOSpinUnlock, 0)
  99         movl            4(%esp), %ecx
 100         movl            $0, (%ecx)
 101         ENABLE_PREEMPTION()
 102         ret
 103 END(_ev_unlock)
 104
 105
 106
 107 /*
 108  * int
 109  * ev_try_lock(p)
 110  *      int *p;
 111  *
 112  * Try to lock p.  Return zero if not successful.
 113  */
 114
 115 LEAF(_ev_try_lock, 0)
 116 LEAF(_IOTrySpinLock, 0)
 117         DISABLE_PREEMPTION()
 118         movl            4(%esp), %ecx
 119         xorl            %eax, %eax
 120         lock
 121         cmpxchgl        %ecx, (%ecx)
 122         jne     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 */