iokit/IOKit/ppc/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  * HISTORY
  35  * 30 Nov   1992    Ben Fathi (benf@next.com)
  36  *      Ported to m98k.
  37  *
  38  * 29 April 1992    Mike Paquette at NeXT
  39  *      Created.
  40  *
  41  * Multiprocessor locks used within the shared memory area between the
  42  * kernel and event system.  These must work in both user and kernel mode.
  43  * The locks are defined in an include file so they get exported to the local
  44  * include file area.
  45  */
  46
  47
  48 #ifndef _IOKIT_IOSHAREDLOCKIMP_H
  49 #define _IOKIT_IOSHAREDLOCKIMP_H
  50
  51 #include <architecture/ppc/asm_help.h>
  52
  53 // 'Till we're building in kernel
  54 .macro DISABLE_PREEMPTION
  55 #ifdef KERNEL
  56 #endif
  57 .endmacro
  58 .macro ENABLE_PREEMPTION
  59 #ifdef KERNEL
  60 #endif
  61 .endmacro
  62
  63 /*
  64  *      void
  65  *      ev_lock(p)
  66  *              register int *p;
  67  *
  68  *      Lock the lock pointed to by p.  Spin (possibly forever) until
  69  *              the lock is available.  Test and test and set logic used.
  70  */
  71         TEXT
  72
  73 #ifndef KERNEL
  74 LEAF(_ev_lock)
  75 LEAF(_IOSpinLock)
  76         li      a6,1            // lock value
  77         lwarx   a7,0,a0         // CEMV10
  78 9:
  79         sync
  80         lwarx   a7,0,a0         // read the lock
  81         cmpwi   cr0,a7,0        // is it busy?
  82         bne-    9b              // yes, spin
  83         sync
  84         stwcx.  a6,0,a0         // try to get the lock
  85         bne-    9b              // failed, try again
  86         isync
  87         blr                     // got it, return
  88 END(_ev_lock)
  89 #endif
  90
  91 /*
  92  *      void
  93  *      spin_unlock(p)
  94  *              int *p;
  95  *
  96  *      Unlock the lock pointed to by p.
  97  */
  98
  99 LEAF(_ev_unlock)
 100 LEAF(_IOSpinUnlock)
 101         sync
 102         li      a7,0
 103         stw     a7,0(a0)
 104         ENABLE_PREEMPTION()
 105         blr
 106 END(_ev_unlock)
 107
 108
 109 /*
 110  *      ev_try_lock(p)
 111  *              int *p;
 112  *
 113  *      Try to lock p.  Return TRUE if successful in obtaining lock.
 114  */
 115
 116 LEAF(_ev_try_lock)
 117 LEAF(_IOTrySpinLock)
 118         li      a6,1            // lock value
 119         DISABLE_PREEMPTION()
 120         lwarx   a7,0,a0         // CEMV10
 121 8:
 122         sync
 123         lwarx   a7,0,a0         // read the lock
 124         cmpwi   cr0,a7,0        // is it busy?
 125         bne-    9f              // yes, give up
 126         sync
 127         stwcx.  a6,0,a0         // try to get the lock
 128         bne-    8b              // failed, try again
 129         li      a0,1            // return TRUE
 130         isync
 131         blr
 132 9:
 133         ENABLE_PREEMPTION()
 134         li      a0,0            // return FALSE
 135         blr
 136 END(_ev_try_lock)
 137
 138 #endif /* ! _IOKIT_IOSHAREDLOCKIMP_H */