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Annotation of XNU/iokit/IOKit/i386/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:  *
        !            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: // 'Till we're building in kernel
        !            53: .macro DISABLE_PREEMPTION
        !            54: #ifdef KERNEL
        !            55: #endif
        !            56: .endmacro
        !            57: .macro ENABLE_PREEMPTION
        !            58: #ifdef KERNEL
        !            59: #endif
        !            60: .endmacro
        !            61: 
        !            62: /* 
        !            63:  * void
        !            64:  * ev_lock(p)
        !            65:  *     int *p;
        !            66:  *
        !            67:  * Lock the lock pointed to by p.  Spin (possibly forever) until the next
        !            68:  * lock is available.
        !            69:  */
        !            70:        TEXT
        !            71: 
        !            72: #ifndef KERNEL
        !            73: LEAF(_ev_lock, 0)
        !            74: LEAF(_IOSpinLock, 0)
        !            75:        push    %eax
        !            76:        push    %ecx
        !            77:        movl    $1, %ecx
        !            78:        movl    12(%esp), %eax  
        !            79: _spin:
        !            80:        xchgl   %ecx,0(%eax)
        !            81:        cmp     $0, %ecx
        !            82:        jne     _spin
        !            83:        pop     %ecx
        !            84:        pop     %eax
        !            85: END(_ev_lock)
        !            86: #endif
        !            87: 
        !            88: /*
        !            89:  * void
        !            90:  * ev_unlock(p)
        !            91:  *     int *p;
        !            92:  *
        !            93:  * Unlock the lock pointed to by p.
        !            94:  */
        !            95: LEAF(_ev_unlock, 0)
        !            96: LEAF(_IOSpinUnlock, 0)
        !            97:        push    %eax
        !            98:        movl    8(%esp),%eax
        !            99:        movl    $0,0(%eax)
        !           100:        ENABLE_PREEMPTION()
        !           101:        pop     %eax
        !           102: END(_ev_unlock)
        !           103: 
        !           104: 
        !           105: 
        !           106: /*
        !           107:  * int
        !           108:  * ev_try_lock(p)
        !           109:  *     int *p;
        !           110:  *
        !           111:  * Try to lock p.  Return zero if not successful.
        !           112:  */
        !           113: 
        !           114: LEAF(_ev_try_lock, 0)
        !           115: LEAF(_IOTrySpinLock, 0)
        !           116:         DISABLE_PREEMPTION()
        !           117:        movl    4(%esp), %eax
        !           118:    lock;bts    $0, 0(%eax)
        !           119:        jb      1f
        !           120:        movl    $1, %eax                /* yes */
        !           121:        ret
        !           122: 1:
        !           123:        ENABLE_PREEMPTION()
        !           124:        xorl    %eax, %eax              /* no */
        !           125: END(_ev_try_lock)
        !           126: 
        !           127: 
        !           128: #endif /* ! _IOKIT_IOSHAREDLOCKIMP_H */

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