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Annotation of kernel/bsd/dev/ppc/EventShmemLock.h, revision 1.1.1.1

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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