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Annotation of XNU/iokit/IOKit/ppc/IOSharedLockImp.h, revision 1.1

1.1     ! root        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 ([email protected])
        !            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 */

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