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Annotation of XNU/iokit/IOKit/i386/IOSharedLockImp.h, revision 1.1.1.1

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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