NIO[SelectableChannel.register和Selector.select会有锁等待冲突]

阅读更多

 

结论： register得放在select之前进行

Thread Dump信息：

"Poller-1" prio=6 tid=0x040f0400 nid=0x408 runnable [0x044df000]

   java.lang.Thread.State: RUNNABLE

        at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)

        at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.j

ava:295)

        at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelector

Impl.java:277)

        at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:158)

        at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:87)

        - locked <0x23b7df70> (a sun.nio.ch.Util$2)

         - locked <0x23b7df60> (a java.util.Collections$UnmodifiableSet)

        - locked <0x23b7dd40> (a sun.nio.ch.WindowsSelectorImpl)

        at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:98)

        at com.zhh.nio.NioServer$Poller.run(NioServer.java:132)

        at java.lang.Thread.run(Thread.java:722)

"Poller-0" prio=6 tid=0x040f0000 nid=0x14e4 runnable [0x0439f000]

   java.lang.Thread.State: RUNNABLE

        at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)

        at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.j

ava:295)

        at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelector

Impl.java:277)

        at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:158)

        at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:87)

        - locked <0x23b77a98> (a sun.nio.ch.Util$2)

        - locked <0x23b77a20> (a java.util.Collections$UnmodifiableSet)

        - locked <0x23b76aa0> (a sun.nio.ch.WindowsSelectorImpl)

        at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:98)

        at com.zhh.nio.NioServer$Poller.run(NioServer.java:132)

        at java.lang.Thread.run(Thread.java:722)

"Acceptor" prio=6 tid=0x040ef800 nid=0x1250 waiting for monitor entry [0x03f1f00

0]

   java.lang.Thread.State: BLOCKED (on object monitor)

        at sun.nio.ch.SelectorImpl.register(SelectorImpl.java:133)

        -  waiting to lock <0x23b7df60> (a java.util.Collections$UnmodifiableSet)

        at java.nio.channels.spi.AbstractSelectableChannel.register(AbstractSele

ctableChannel.java:207)

        - locked <0x23b8da18> (a java.lang.Object)

        at java.nio.channels.SelectableChannel.register(SelectableChannel.java:2

77)

        at com.zhh.nio.NioSession.register(NioSession.java:50)

        at com.zhh.nio.NioServer$Poller.register(NioServer.java:123)

        at com.zhh.nio.NioServer.handleNewSession(NioServer.java:222)

        at com.zhh.nio.NioServer$Acceptor.run(NioServer.java:236)

        at java.lang.Thread.run(Thread.java:722)

Code层面：

select：

private int lockAndDoSelect(long timeout) throws IOException {

        synchronized (this) {

            if (!isOpen())

                throw new ClosedSelectorException();

             synchronized (publicKeys) {

                synchronized (publicSelectedKeys) {

                    return doSelect(timeout);

                }

            }

        }

    }

register：

 protected final SelectionKey register(AbstractSelectableChannel ch,

                                          int ops,

                                          Object attachment)

    {

        if (!(ch instanceof SelChImpl))

            throw new IllegalSelectorException();

        SelectionKeyImpl k = new SelectionKeyImpl((SelChImpl)ch, this);

        k.attach(attachment);

         synchronized (publicKeys) {

            implRegister(k);

        }

        k.interestOps(ops);

        return k;

    }