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Annotation of XNU/iokit/Kernel/IOConditionLock.cpp, 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: /* Copyright (c) 1997 Apple Computer, Inc.  All rights reserved.
        !            23:  * Copyright (c) 1994-1996 NeXT Software, Inc.  All rights reserved. 
        !            24:  *
        !            25:  * AppleIOPSSafeCondLock.m. Lock object with exported condition variable, 
        !            26:  *     kernel version.
        !            27:  *
        !            28:  * HISTORY
        !            29:  * 1997-11-
        !            30:  * 01-Aug-91    Doug Mitchell at NeXT
        !            31:  *      Created. 
        !            32:  */
        !            33: 
        !            34: #include <IOKit/IOConditionLock.h>
        !            35: 
        !            36: #define super OSObject
        !            37: OSDefineMetaClassAndStructors(IOConditionLock, OSObject)
        !            38: 
        !            39: bool IOConditionLock::initWithCondition(int inCondition, bool inIntr = true)
        !            40: {
        !            41:     if (!super::init())
        !            42:         return false;
        !            43: 
        !            44:     cond_interlock = IOLockAlloc();
        !            45:     sleep_interlock = IOLockAlloc();
        !            46: 
        !            47:     condition = inCondition;
        !            48:     want_lock    = false;
        !            49:     waiting      = false;
        !            50:     interruptible = (inIntr) ? THREAD_INTERRUPTIBLE : THREAD_UNINT;
        !            51: 
        !            52:     return cond_interlock && sleep_interlock;
        !            53: }
        !            54: 
        !            55: IOConditionLock *IOConditionLock::withCondition(int condition, bool intr = true)
        !            56: {
        !            57:     IOConditionLock *me = new IOConditionLock;
        !            58: 
        !            59:     if (me && !me->initWithCondition(condition, intr)) {
        !            60:         me->free();
        !            61:         return 0;
        !            62:     }
        !            63: 
        !            64:     return me;
        !            65: }
        !            66: void IOConditionLock::free()
        !            67: {
        !            68:     if (cond_interlock)
        !            69:         IOLockFree(cond_interlock);
        !            70:     if (sleep_interlock)
        !            71:         IOLockFree(sleep_interlock);
        !            72:     super::free();
        !            73: }
        !            74: 
        !            75: bool IOConditionLock::getInterruptible() const
        !            76: {
        !            77:     return interruptible;
        !            78: }
        !            79: 
        !            80: int IOConditionLock:: getCondition() const
        !            81: {
        !            82:     return condition;
        !            83: }
        !            84: 
        !            85: int IOConditionLock:: setCondition(int inCondition)
        !            86: {
        !            87:     int old = condition;
        !            88: 
        !            89:     condition = inCondition;
        !            90:     thread_wakeup_one((void *) &condition);
        !            91: 
        !            92:     return old;
        !            93: }
        !            94: 
        !            95: void IOConditionLock::unlock()
        !            96: {
        !            97:     IOTakeLock(sleep_interlock);
        !            98: 
        !            99:     thread_wakeup_one((void *) &condition);
        !           100: 
        !           101:     want_lock = false;
        !           102:     if (waiting) {
        !           103:        waiting = false;
        !           104:        thread_wakeup(this);    // Wakeup everybody
        !           105:     }
        !           106: 
        !           107:     IOUnlock(sleep_interlock);
        !           108: }
        !           109: 
        !           110: void IOConditionLock::unlockWith(int inCondition)
        !           111: {
        !           112:     IOTakeLock(sleep_interlock);
        !           113:     IOTakeLock(cond_interlock);
        !           114:     
        !           115:     condition = inCondition;
        !           116: 
        !           117:     IOUnlock(cond_interlock);
        !           118:     IOUnlock(sleep_interlock);
        !           119: 
        !           120:     unlock();
        !           121: }
        !           122: 
        !           123: bool IOConditionLock::tryLock()
        !           124: {
        !           125:     bool result;
        !           126: 
        !           127:     IOTakeLock(sleep_interlock);
        !           128: 
        !           129:     result = !want_lock;
        !           130:     if (result)
        !           131:        want_lock = true;
        !           132: 
        !           133:     IOUnlock(sleep_interlock);
        !           134: 
        !           135:     return result;
        !           136: }
        !           137: 
        !           138: int IOConditionLock::lock()
        !           139: {
        !           140:     int thread_res = THREAD_AWAKENED;
        !           141: 
        !           142:     IOTakeLock(sleep_interlock);
        !           143:     
        !           144:     /* Try to acquire the want_lock bit. */
        !           145:     while (want_lock && thread_res == THREAD_AWAKENED)
        !           146:     {
        !           147:        waiting = true;
        !           148: 
        !           149:         assert_wait((void *) this, interruptible);     /* assert event */
        !           150:        IOUnlock(sleep_interlock);                      /* release the lock */
        !           151:        thread_block((void (*)(void)) 0);               /* block ourselves */
        !           152: 
        !           153:         IOTakeLock(sleep_interlock);
        !           154:        thread_res = thread_wait_result();
        !           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_block((void (*)(void)) 0);               /* block ourselves */
        !           197: 
        !           198:        thread_res = thread_wait_result();
        !           199:     } while (thread_res == THREAD_AWAKENED);
        !           200:     
        !           201:     return thread_res;
        !           202: }

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