iokit/Kernel/IOConditionLock.cpp

   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         IOLockWakeup(sleep_interlock, this, /* one-thread */ false);    // 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         thread_res = IOLockSleep(sleep_interlock, (void *) this, interruptible);
 149     }
 150     if (thread_res == THREAD_AWAKENED)
 151         want_lock = true;
 152
 153     IOUnlock(sleep_interlock);
 154
 155     return thread_res;
 156 }
 157
 158 int IOConditionLock::lockWhen(int inCondition)
 159 {
 160     int thread_res;
 161
 162     do
 163     {
 164         /* First get the actual lock */
 165         thread_res = lock();
 166         if (thread_res != THREAD_AWAKENED)
 167             break;      // Failed to acquire lock
 168
 169         if (inCondition == condition)
 170             break;      // Hold lock and condition is expected value
 171
 172         /*
 173          * Need to hold a IOTakeLock when we call thread_sleep().
 174          * Both _cond_interlock and want_lock must be held to
 175          * change _condition.
 176          */
 177         IOTakeLock(cond_interlock);
 178         unlock();       // Release lock and sleep
 179
 180         /*
 181          * this is the critical section on a multi in which
 182          * another thread could hold _sleep_interlock, but they
 183          * can't change _condition. Holding _cond_interlock here
 184          * (until after assert_wait() is called from
 185          * thread_sleep()) ensures that we'll be notified
 186          * of changes in _condition.
 187          */
 188         assert_wait((void *) &condition, interruptible); /* assert event */
 189         IOUnlock(cond_interlock);                        /* release the lock */
 190         thread_res = thread_block(THREAD_CONTINUE_NULL); /* block ourselves */
 191     } while (thread_res == THREAD_AWAKENED);
 192
 193     return thread_res;
 194 }