1 | /* |
2 | * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved. |
3 | * |
4 | * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ |
5 | * |
6 | * This file contains Original Code and/or Modifications of Original Code |
7 | * as defined in and that are subject to the Apple Public Source License |
8 | * Version 2.0 (the 'License'). You may not use this file except in |
9 | * compliance with the License. The rights granted to you under the License |
10 | * may not be used to create, or enable the creation or redistribution of, |
11 | * unlawful or unlicensed copies of an Apple operating system, or to |
12 | * circumvent, violate, or enable the circumvention or violation of, any |
13 | * terms of an Apple operating system software license agreement. |
14 | * |
15 | * Please obtain a copy of the License at |
16 | * http://www.opensource.apple.com/apsl/ and read it before using this file. |
17 | * |
18 | * The Original Code and all software distributed under the License are |
19 | * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER |
20 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, |
21 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, |
22 | * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. |
23 | * Please see the License for the specific language governing rights and |
24 | * limitations under the License. |
25 | * |
26 | * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ |
27 | */ |
28 | /* Copyright (c) 1997 Apple Computer, Inc. All rights reserved. |
29 | * Copyright (c) 1994-1996 NeXT Software, Inc. All rights reserved. |
30 | * |
31 | * AppleIOPSSafeCondLock.m. Lock object with exported condition variable, |
32 | * kernel version. |
33 | * |
34 | * HISTORY |
35 | * 1997-11- |
36 | * 01-Aug-91 Doug Mitchell at NeXT |
37 | * Created. |
38 | */ |
39 | |
40 | #include <IOKit/IOConditionLock.h> |
41 | |
42 | #define super OSObject |
43 | OSDefineMetaClassAndStructors(IOConditionLock, OSObject) |
44 | |
45 | bool IOConditionLock::initWithCondition(int inCondition, bool inIntr) |
46 | { |
47 | if (!super::init()) |
48 | return false; |
49 | |
50 | cond_interlock = IOLockAlloc(); |
51 | sleep_interlock = IOLockAlloc(); |
52 | |
53 | condition = inCondition; |
54 | want_lock = false; |
55 | waiting = false; |
56 | interruptible = (inIntr) ? THREAD_INTERRUPTIBLE : THREAD_UNINT; |
57 | |
58 | return cond_interlock && sleep_interlock; |
59 | } |
60 | |
61 | IOConditionLock *IOConditionLock::withCondition(int condition, bool intr) |
62 | { |
63 | IOConditionLock *me = new IOConditionLock; |
64 | |
65 | if (me && !me->initWithCondition(condition, intr)) { |
66 | me->release(); |
67 | return 0; |
68 | } |
69 | |
70 | return me; |
71 | } |
72 | void IOConditionLock::free() |
73 | { |
74 | if (cond_interlock) |
75 | IOLockFree(cond_interlock); |
76 | if (sleep_interlock) |
77 | IOLockFree(sleep_interlock); |
78 | super::free(); |
79 | } |
80 | |
81 | bool IOConditionLock::getInterruptible() const |
82 | { |
83 | return interruptible; |
84 | } |
85 | |
86 | int IOConditionLock:: getCondition() const |
87 | { |
88 | return condition; |
89 | } |
90 | |
91 | int IOConditionLock:: setCondition(int inCondition) |
92 | { |
93 | int old = condition; |
94 | |
95 | condition = inCondition; |
96 | thread_wakeup_one((void *) &condition); |
97 | |
98 | return old; |
99 | } |
100 | |
101 | void IOConditionLock::unlock() |
102 | { |
103 | IOTakeLock(sleep_interlock); |
104 | |
105 | thread_wakeup_one((void *) &condition); |
106 | |
107 | want_lock = false; |
108 | if (waiting) { |
109 | waiting = false; |
110 | IOLockWakeup(sleep_interlock, this, /* one-thread */ false); // Wakeup everybody |
111 | } |
112 | |
113 | IOUnlock(sleep_interlock); |
114 | } |
115 | |
116 | void IOConditionLock::unlockWith(int inCondition) |
117 | { |
118 | IOTakeLock(sleep_interlock); |
119 | IOTakeLock(cond_interlock); |
120 | |
121 | condition = inCondition; |
122 | |
123 | IOUnlock(cond_interlock); |
124 | IOUnlock(sleep_interlock); |
125 | |
126 | unlock(); |
127 | } |
128 | |
129 | bool IOConditionLock::tryLock() |
130 | { |
131 | bool result; |
132 | |
133 | IOTakeLock(sleep_interlock); |
134 | |
135 | result = !want_lock; |
136 | if (result) |
137 | want_lock = true; |
138 | |
139 | IOUnlock(sleep_interlock); |
140 | |
141 | return result; |
142 | } |
143 | |
144 | int IOConditionLock::lock() |
145 | { |
146 | int thread_res = THREAD_AWAKENED; |
147 | |
148 | IOTakeLock(sleep_interlock); |
149 | |
150 | /* Try to acquire the want_lock bit. */ |
151 | while (want_lock && thread_res == THREAD_AWAKENED) |
152 | { |
153 | waiting = true; |
154 | thread_res = IOLockSleep(sleep_interlock, (void *) this, interruptible); |
155 | } |
156 | if (thread_res == THREAD_AWAKENED) |
157 | want_lock = true; |
158 | |
159 | IOUnlock(sleep_interlock); |
160 | |
161 | return thread_res; |
162 | } |
163 | |
164 | int IOConditionLock::lockWhen(int inCondition) |
165 | { |
166 | int thread_res; |
167 | |
168 | do |
169 | { |
170 | /* First get the actual lock */ |
171 | thread_res = lock(); |
172 | if (thread_res != THREAD_AWAKENED) |
173 | break; // Failed to acquire lock |
174 | |
175 | if (inCondition == condition) |
176 | break; // Hold lock and condition is expected value |
177 | |
178 | /* |
179 | * Need to hold a IOTakeLock when we call thread_sleep(). |
180 | * Both _cond_interlock and want_lock must be held to |
181 | * change _condition. |
182 | */ |
183 | IOTakeLock(cond_interlock); |
184 | unlock(); // Release lock and sleep |
185 | |
186 | /* |
187 | * this is the critical section on a multi in which |
188 | * another thread could hold _sleep_interlock, but they |
189 | * can't change _condition. Holding _cond_interlock here |
190 | * (until after assert_wait() is called from |
191 | * thread_sleep()) ensures that we'll be notified |
192 | * of changes in _condition. |
193 | */ |
194 | assert_wait((void *) &condition, interruptible); /* assert event */ |
195 | IOUnlock(cond_interlock); /* release the lock */ |
196 | thread_res = thread_block(THREAD_CONTINUE_NULL); /* block ourselves */ |
197 | } while (thread_res == THREAD_AWAKENED); |
198 | |
199 | return thread_res; |
200 | } |
201 | |