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 /*
  53  * void
  54  * ev_lock(p)
  55  *      int *p;
  56  *
  57  * Lock the lock pointed to by p.  Spin (possibly forever) until the next
  58  * lock is available.
  59  */
  60         TEXT
  61
  62 #ifndef KERNEL
  63 LEAF(_ev_lock, 0)
  64 LEAF(_IOSpinLock, 0)
  65         movl            4(%esp), %ecx
  66 0:
  67         xorl            %eax, %eax
  68         rep
  69         nop             /* pause for hyperthreaded CPU's */
  70         lock
  71         cmpxchgl        %ecx, (%ecx)
  72         jne             0b
  73         ret
  74 END(_ev_lock)
  75 #endif
  76
  77 /*
  78  * void
  79  * ev_unlock(p)
  80  *      int *p;
  81  *
  82  * Unlock the lock pointed to by p.
  83  */
  84 LEAF(_ev_unlock, 0)
  85 LEAF(_IOSpinUnlock, 0)
  86         movl            4(%esp), %ecx
  87         movl            $0, (%ecx)
  88         ret
  89 END(_ev_unlock)
  90
  91
  92
  93 /*
  94  * int
  95  * ev_try_lock(p)
  96  *      int *p;
  97  *
  98  * Try to lock p.  Return zero if not successful.
  99  */
 100
 101 LEAF(_ev_try_lock, 0)
 102 LEAF(_IOTrySpinLock, 0)
 103         movl            4(%esp), %ecx
 104         xorl            %eax, %eax
 105         lock
 106         cmpxchgl        %ecx, (%ecx)
 107         jne     1f
 108         movl    $1, %eax                /* yes */
 109         ret
 110 1:
 111         xorl    %eax, %eax              /* no */
 112 END(_ev_try_lock)
 113
 114
 115 #endif /* ! _IOKIT_IOSHAREDLOCKIMP_H */