阻塞lock的基本流程
if(cas(0,acquire))
setExclusiveOwnerThread
else if(current==getExclusiveOnwerThread) {
setState(c+acquires)
}
addWaiter
park
........................
for(;;) {
p = node.predecessorif(p==head&&tryAcquire(arg)){
setHead(node)return
}park
}
阻塞release的基本流程
if(current!=getExclusiveOnwerThread){
IllegalMonitorStateException
}
if(c == 0){
setExclusive(null)
free = true
}
setState(c)
return free
unparkSuccessor(LockSupport.unpark(thread))
非阻塞lock的基本流程
if(cas(0,acquire))
setExclusiveOwnerThread true
else if(current==getExclusiveOwnerThread)
setState(c+acquire) true
false
非阻塞的release的基本流程
与阻塞的release流程相同
阻塞共享lock的基本流程
tryAcquireShared(acquires){
for(;;) {
remaining = state-acquires
if(remaining<0 || CAS(state,remaining))
return remaining
}
}
if(tryAcquireShared(arg)<0){
node = addWaiter(Node.SHARED)
for(;;) {
p = node.predecessorpropagate = tryAcquireShared(arg)if(p==head&&propagate>=0){
setHead(node)if(propagate>0||next==null||next.isShared())//如果还有剩余,继续唤醒接下来一个节点doReleaseShared()return
}park
}
}
阻塞共享release的基本流程
tryReleaseShared(acquires){
for(;;){if(cas(state,state+acquires))return true}
}
if(tryReleaseShared(acquires)) {
unparkSuccessor(h)
}
共享lock的基本模式
覆盖tryAcquireShared方法
for(;;) { if(state-acquire<0) { false } if(cas(state,state-acquires)) { true } }
共享lock的release的基本模式
覆盖tryReleaseShared方法
for(;;) { if(cas(state,state+acquires)) { true } }排它lock的基本模式
覆盖tryAcquire方法
if(state==0) { if(cas(state, state+acquire)) { setExclusiveOwnerThread(current) return true } } else if(current==getExclusiveOwnerThread) { if(cas(state, state+acquire)) { return true } } return flase排它lock的release基本模式
覆盖tryRelease方法
if(current != getExclusiveThread) { throw new IllegalMonitorStateException() } nextc = state-release if(nextc == 0) { setState(nextc) setExclusiveOwnerThread(current) return true } else { setState(nextc) return false }