Name: nt126004			Date: 04/17/2003


FULL PRODUCT VERSION :
java version "1.4.2-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2-beta-b19)
Java HotSpot(TM) Client VM (build 1.4.2-beta-b19, mixed mode)

FULL OS VERSION :
Microsoft Windows 2000 [Version 5.00.2195]

A DESCRIPTION OF THE PROBLEM :
Blocking Selector stops Blocking occasionally.

It would appear that when wakeup() is called at a certain point then the selector.select() method starts returning instantly with no selected keys from then on.

This problem is difficult to consistantly reproduce hence it is difficult to track down the exact cause of the problem.

It is a very serious problem for anyone using blocking io as the cpu usage jumps to 100%.

As it is difficult to produce a small test case I have done some research to help find the bug:

* once the problem is occuring the following debug information is available:
keys == {key with interestOps == 1 fd == 1788}
cancelledKeys == {}
sourceFD == 1552
sinkFD == 1600
interruptTriggered == false
timeout == -1
threads == {}
2 channels
exceptIDs == {0, 0, 0, ...}
readIDs == {1, 1552, 1788, 0, 0, 0, ...}
writeIDs == {0, 1788, 0, 0, 0, ...}

* the trace through the code of WindowsSelectorImpl doSelect(long aTimout)
1) calls processDeregisterQueue();
2) calls adjustThreadsCount();
3) calls finishLock.reset();
4) calls startLock.startThreads();
5) calls begin();
6) calls subSelector.poll(); (this doesn't block, I guess this is the problem)
7) calls end();
8) calls resetWakeupSocket();
9) calls finishLock.checkForException();
10) calls processDeregisterQueue();
11) calls updateSelectedKeys();
12) returns 0

Note the same problem also exists in JDK1.4.1_02 (I though maybe the synchronization changes would have fixed it, however they didn't)
This is a replacement bug for review ID: 183301 (review id 183301 is no longer important)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Difficult to provide a test case due to the nature of the problem.
I have only been able to reproduce the problem when wakeup() has been called.
It is too difficult to establish at what point in select() the code is up to when wakeup() causes the problem.

EXPECTED VERSUS ACTUAL BEHAVIOR :
when no keys are ready to be selected select() to block again until keys become ready for selection or wakeup/interrupt is called.
select() returns no keys without blocking

REPRODUCIBILITY :
This bug can be reproduced occasionally.

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Difficult to make small test case, however we are able to reproduce the problem occasionally with our actual code, hence I can provide more debug info if what is provided in the desription is not enough.  This is a very serious problem for everone relying on select() to block, hence I will try to answer questions about this ASAP.
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(Review ID: 183670) 
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