RFR JDK-8162497 "Deadlock in obtainSendWindow"

[Sergey Kuksenko]

Hi,

Could you please review the following fix for JDK-8162497?

http://cr.openjdk.java.net/~skuksenko/jep110/8162497/webrev.00/

https://bugs.openjdk.java.net/browse/JDK-8162497

The issue:

Current implementation of "obtainSendWindow" and Stream "sendWindow" 
doesn't provide atomicity for "take" operation due to natural randomness 
of "wait/notifyAll" operations.
When multiple threads are trying to get a portion of sendWindow (calling 
"obtainSendWindow"), each thread may capture and hold amount of send 
window which is not enough to send its own data causing continue waiting 
and exhausting whole sending window. And all threads are blocked on 
obtainSendWindow.
At the same moment overall sending window is large enough to send data 
and server doesn't send WINDOW_UPDATE frame.

For example:
- 32 threads
- max data frame size is 16K.
- connection send window is 64K-1.
- each thread is trying to send more than 1 full size data frame.
At this situation each thread captures and holds ~1K-3K portion of 
sending window, full sending window is exhausted and each sending thread 
is waiting (forever) to reach 16K.


Thank you,

Sergey Kuksenko.