InterProcessReadWriteLock allows the write lock to be taken when the read one is not released

Hi,

I have the following piece of code

01. rwLock.readLock().acquire();
02.
03. if (data needs to be refreshed) {
04.  rwLock.readLock().release(); // releaseing read lock becore acquire write one
05.  rwLock.writeLock().acquire();
06.  if (data needs to be refreshed) { // check again
07.     try {
08.       // refresh data
09.       rwLock.readLock().acquire();
10.     } finally {
11.       rwLock.writeLock().release();
12.     }
13.  }
14.  try {
15.   // read data
16.  } finally {
17.      rwLock.readLock().release();
18.  }
19. }

this is the standard read/write lock syntax described here https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/locks/ReentrantReadWriteLock.html

I noticed that when 2 processes run that code, if they both try to execute

05. rwLock.writeLock().acquire();

as expected only one goes through, but as soon the process that went through releases the write lock

11. rwLock.writeLock().release();

then the other process is able to acquire it and goes to line 06! Even if the first process acquired a read lock just before:

09. rwLock.readLock().acquire();

I tested the same code using 2 threads on the same jvm rather than 2 processes and behaves the same.

Then I tested 2 threads using the non distributed ReentrantReadWriteLock provided with java, and that one behaves correctly not allowing the second thread to lock on the write lock until the first thread releases its read lock.