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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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