实现锁和条件变量.doc

用Sleep来实现锁和条件变量/ Dummy functions - so we can compile our later assignments / Note - without a correct implementation of Condition:Wait(), / the test case in the network assignment wont work!Lock:Lock(char* debugName) name = debugName; lock = FALSE; holder = NULL; queue = new List;Lock:Lock() delete queue;void Lock:Acquire() ASSERT(!isHeldByCurrentThread(); /如果当前线程没有获得锁 IntStatus oldLevel = interrupt-SetLevel(IntOff);/ disable interruptswhile (lock) / lock not available queue-Append(void *)currentThread);/ so go to sleep currentThread-Sleep(); lock = TRUE;/ lock available, / consume its value holder = currentThread; (void) interrupt-SetLevel(oldLevel);/ re-enable interruptsvoid Lock:Release() Thread *thread; ASSERT(isHeldByCurrentThread(); /如果表达式为假，则终止程序运行 IntStatus oldLevel = interrupt-SetLevel(IntOff); thread = (Thread *)queue-Remove(); if (thread != NULL) / make thread ready, consuming the V immediately scheduler-ReadyToRun(thread); lock = FALSE; holder = NULL; (void) interrupt-SetLevel(oldLevel);bool Lock:isHeldByCurrentThread() return (holder = currentThread);Condition:Condition(char* debugName) name = debugName; queue = new List;Condition:Condition() delete queue;void Condition:Wait(Lock* conditionLock) ASSERT(conditionLock-isHeldByCurrentThread(); IntStatus oldLevel = interrupt-SetLevel(IntOff);/ disable interrupts conditionLock-Release(); queue-Append(void *)currentThread);/ so go to sleep currentThread-Sleep(); (void) interrupt-SetLevel(oldLevel);/ re-enable interrupts conditionLock-Acquire();void Condition:Signal(Lock* conditionLock) Thread *thread; ASSERT(conditionLock-isHeldByCurrentThread(); thread = (Thread *)queue-Remove(); if (thread != NULL) / make thread ready, consuming the V immediately scheduler-ReadyToRun(thread);void Condition:Broadcast(Lock* conditionLock) Thread *thread; ASSERT(conditionLock-isHeldByCurrentThread(); do thread = (Thread *)queue-Remove(); if (thread != NULL) / make thread ready, consuming the V immediately scheduler-ReadyToRun(thread); while(thread != NULL);用信号量来实现条件变量/ Dummy functions - so we can compile our later assignments / Note - without a correct implementation of Condition:Wait(), / the test case in the network assignment wont work!Lock:Lock(char* debugName) name = debugName; holder = NULL; semlock = new Semaphore(debugName, 1);Lock:Lock() delete semlock;void Lock:Acquire() ASSERT(!isHeldByCurrentThread(); semlock-P(); holder = currentThread;void Lock:Release() ASSERT(isHeldByCurrentThread(); holder = NULL; semlock-V();bool Lock:isHeldByCurrentThread() return (holder = currentThread);Condition:Condition(char* debugName) name = debugName; semcond = new Semaphore(debugName, 0); count = 0;Condition:Condition() delete semcond;void Condition:Wait(Lock* conditionLock) ASSERT(conditionLock-isHeldByCurrentThread(); count+; conditionLock-Release(); semcond-P(); conditionLock-Acquire();void Condition:Signal(Lock* conditionLock) ASSERT(conditionLock-isHeldByCurrentThread(); if