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Annotation of kernel/bsd/dev/ppc/EventShmemLock.h, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: 
        !            25: /*     Copyright (c) 1992 NeXT Computer, Inc.  All rights reserved. 
        !            26:  *
        !            27:  * EventShmemLock.h -  Shared memory area locks for use between the
        !            28:  *                     WindowServer and the Event Driver.
        !            29:  *
        !            30:  * HISTORY
        !            31:  * 30 Nov   1992    Ben Fathi ([email protected])
        !            32:  *      Ported to m98k.
        !            33:  *
        !            34:  * 29 April 1992    Mike Paquette at NeXT
        !            35:  *      Created. 
        !            36:  *
        !            37:  * Multiprocessor locks used within the shared memory area between the
        !            38:  * kernel and event system.  These must work in both user and kernel mode.
        !            39:  * The locks are defined in an include file so they get exported to the local
        !            40:  * include file area.
        !            41:  */
        !            42: #ifdef KERNEL_PRIVATE
        !            43: #import        <architecture/ppc/asm_help.h>
        !            44: #import        <architecture/ppc/pseudo_inst.h>
        !            45: 
        !            46: /*
        !            47:  *     void
        !            48:  *     ev_lock(p)
        !            49:  *             register int *p;
        !            50:  *
        !            51:  *     Lock the lock pointed to by p.  Spin (possibly forever) until
        !            52:  *             the lock is available.  Test and test and set logic used.
        !            53:  */
        !            54:        TEXT
        !            55: 
        !            56: LEAF(_ev_lock)
        !            57:        li      a6,1            // lock value
        !            58: 9:
        !            59:        sync
        !            60:        lwarx   a7,0,a0         // read the lock
        !            61:        cmpwi   cr0,a7,0        // is it busy?
        !            62:        bne-    9b              // yes, spin
        !            63:        sync
        !            64:        stwcx.  a6,0,a0         // try to get the lock
        !            65:        bne-    9b              // failed, try again
        !            66:        isync
        !            67:        blr                     // got it, return
        !            68: END(_ev_lock)
        !            69: 
        !            70: /*
        !            71:  *     void
        !            72:  *     spin_unlock(p)
        !            73:  *             int *p;
        !            74:  *
        !            75:  *     Unlock the lock pointed to by p.
        !            76:  */
        !            77: 
        !            78: LEAF(_ev_unlock)
        !            79:        sync
        !            80:        li      a7,0
        !            81:        stw     a7,0(a0)
        !            82:        blr
        !            83: END(_ev_unlock)
        !            84: 
        !            85: 
        !            86: /*
        !            87:  *     ev_try_lock(p)
        !            88:  *             int *p;
        !            89:  *
        !            90:  *     Try to lock p.  Return TRUE if successful in obtaining lock.
        !            91:  */
        !            92: 
        !            93: LEAF(_ev_try_lock)
        !            94:        li      a6,1            // lock value
        !            95: 8:
        !            96:        sync
        !            97:        lwarx   a7,0,a0         // read the lock
        !            98:        cmpwi   cr0,a7,0        // is it busy?
        !            99:        bne-    9f              // yes, give up
        !           100:        sync
        !           101:        stwcx.  a6,0,a0         // try to get the lock
        !           102:        bne-    8b              // failed, try again
        !           103:        li      a0,1            // return TRUE
        !           104:        isync
        !           105:        blr
        !           106: 9:
        !           107:        li      a0,0            // return FALSE
        !           108:        blr
        !           109: END(_ev_try_lock)
        !           110: #endif /* KERNEL_PRIVATE */

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