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 |
46 | IOConditionLock::initWithCondition(int inCondition, bool inIntr) |
47 | { |
48 | if (!super::init()) { |
49 | return false; |
50 | } |
51 | |
52 | cond_interlock = IOLockAlloc(); |
53 | sleep_interlock = IOLockAlloc(); |
54 | |
55 | condition = inCondition; |
56 | want_lock = false; |
57 | waiting = false; |
58 | interruptible = (inIntr) ? THREAD_INTERRUPTIBLE : THREAD_UNINT; |
59 | |
60 | return cond_interlock && sleep_interlock; |
61 | } |
62 | |
63 | IOConditionLock * |
64 | IOConditionLock::withCondition(int condition, bool intr) |
65 | { |
66 | IOConditionLock *me = new IOConditionLock; |
67 | |
68 | if (me && !me->initWithCondition(inCondition: condition, inIntr: intr)) { |
69 | me->release(); |
70 | return NULL; |
71 | } |
72 | |
73 | return me; |
74 | } |
75 | void |
76 | IOConditionLock::free() |
77 | { |
78 | if (cond_interlock) { |
79 | IOLockFree(lock: cond_interlock); |
80 | } |
81 | if (sleep_interlock) { |
82 | IOLockFree(lock: sleep_interlock); |
83 | } |
84 | super::free(); |
85 | } |
86 | |
87 | bool |
88 | IOConditionLock::getInterruptible() const |
89 | { |
90 | return interruptible; |
91 | } |
92 | |
93 | int |
94 | IOConditionLock:: getCondition() const |
95 | { |
96 | return condition; |
97 | } |
98 | |
99 | int |
100 | IOConditionLock:: setCondition(int inCondition) |
101 | { |
102 | int old = condition; |
103 | |
104 | condition = inCondition; |
105 | thread_wakeup_one((void *) &condition); |
106 | |
107 | return old; |
108 | } |
109 | |
110 | void |
111 | IOConditionLock::unlock() |
112 | { |
113 | IOTakeLock(lock: sleep_interlock); |
114 | |
115 | thread_wakeup_one((void *) &condition); |
116 | |
117 | want_lock = false; |
118 | if (waiting) { |
119 | waiting = false; |
120 | IOLockWakeup(lock: sleep_interlock, event: this, /* one-thread */ oneThread: false); // Wakeup everybody |
121 | } |
122 | |
123 | IOUnlock(lock: sleep_interlock); |
124 | } |
125 | |
126 | void |
127 | IOConditionLock::unlockWith(int inCondition) |
128 | { |
129 | IOTakeLock(lock: sleep_interlock); |
130 | IOTakeLock(lock: cond_interlock); |
131 | |
132 | condition = inCondition; |
133 | |
134 | IOUnlock(lock: cond_interlock); |
135 | IOUnlock(lock: sleep_interlock); |
136 | |
137 | unlock(); |
138 | } |
139 | |
140 | bool |
141 | IOConditionLock::tryLock() |
142 | { |
143 | bool result; |
144 | |
145 | IOTakeLock(lock: sleep_interlock); |
146 | |
147 | result = !want_lock; |
148 | if (result) { |
149 | want_lock = true; |
150 | } |
151 | |
152 | IOUnlock(lock: sleep_interlock); |
153 | |
154 | return result; |
155 | } |
156 | |
157 | int |
158 | IOConditionLock::lock() |
159 | { |
160 | int thread_res = THREAD_AWAKENED; |
161 | |
162 | IOTakeLock(lock: sleep_interlock); |
163 | |
164 | /* Try to acquire the want_lock bit. */ |
165 | while (want_lock && thread_res == THREAD_AWAKENED) { |
166 | waiting = true; |
167 | thread_res = IOLockSleep(lock: sleep_interlock, event: (void *) this, interType: interruptible); |
168 | } |
169 | if (thread_res == THREAD_AWAKENED) { |
170 | want_lock = true; |
171 | } |
172 | |
173 | IOUnlock(lock: sleep_interlock); |
174 | |
175 | return thread_res; |
176 | } |
177 | |
178 | int |
179 | IOConditionLock::lockWhen(int inCondition) |
180 | { |
181 | int thread_res; |
182 | |
183 | do{ |
184 | /* First get the actual lock */ |
185 | thread_res = lock(); |
186 | if (thread_res != THREAD_AWAKENED) { |
187 | break; // Failed to acquire lock |
188 | } |
189 | if (inCondition == condition) { |
190 | break; // Hold lock and condition is expected value |
191 | } |
192 | /* |
193 | * Need to hold a IOTakeLock when we call thread_sleep(). |
194 | * Both _cond_interlock and want_lock must be held to |
195 | * change _condition. |
196 | */ |
197 | IOTakeLock(lock: cond_interlock); |
198 | unlock(); // Release lock and sleep |
199 | |
200 | /* |
201 | * this is the critical section on a multi in which |
202 | * another thread could hold _sleep_interlock, but they |
203 | * can't change _condition. Holding _cond_interlock here |
204 | * (until after assert_wait() is called from |
205 | * thread_sleep()) ensures that we'll be notified |
206 | * of changes in _condition. |
207 | */ |
208 | assert_wait(event: (void *) &condition, interruptible); /* assert event */ |
209 | IOUnlock(lock: cond_interlock); /* release the lock */ |
210 | thread_res = thread_block(THREAD_CONTINUE_NULL); /* block ourselves */ |
211 | } while (thread_res == THREAD_AWAKENED); |
212 | |
213 | return thread_res; |
214 | } |
215 | |