WriterPreferenceReadWriteLock (Web API 2021)

java.lang.Object
- com.microstrategy.utils.concurrent.WriterPreferenceReadWriteLock

All Implemented Interfaces:

ReadWriteLock

Direct Known Subclasses:

ReentrantWriterPreferenceReadWriteLock
```
public class WriterPreferenceReadWriteLock
extends java.lang.Object
implements ReadWriteLock
```
A ReadWriteLock that prefers waiting writers over waiting readers when there is contention. This class is adapted from the versions described in CPJ, improving on the ones there a bit by segregating reader and writer wait queues, which is typically more efficient.
The locks are NOT reentrant. In particular, even though it may appear to usually work OK, a thread holding a read lock should not attempt to re-acquire it. Doing so risks lockouts when there are also waiting writers.
[ Introduction to this package. ]

Since:

MicroStrategy Web 7.3.1 or earlier

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`protected class`	`WriterPreferenceReadWriteLock.ReaderLock`
`protected class`	`WriterPreferenceReadWriteLock.Signaller`	Reader and Writer requests are maintained in two different wait sets, by two different objects.
`protected class`	`WriterPreferenceReadWriteLock.WriterLock`

Field Summary

Fields
Modifier and Type	Field	Description
`protected long`	`activeReaders_`
`protected java.lang.Thread`	`activeWriter_`
`protected WriterPreferenceReadWriteLock.ReaderLock`	`readerLock_`
`protected long`	`waitingReaders_`
`protected long`	`waitingWriters_`
`protected WriterPreferenceReadWriteLock.WriterLock`	`writerLock_`

Constructor Summary

Constructors
Constructor Description

WriterPreferenceReadWriteLock()

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`protected boolean`	`allowReader()`	Override this method to change to reader preference *
`protected void`	`cancelledWaitingReader()`
`protected void`	`cancelledWaitingWriter()`
`protected WriterPreferenceReadWriteLock.Signaller`	`endRead()`	Called upon termination of a read.
`protected WriterPreferenceReadWriteLock.Signaller`	`endWrite()`	Called upon termination of a write.
`Sync`	`readLock()`	get the readLock *
`protected boolean`	`startRead()`
`protected boolean`	`startReadFromNewReader()`
`protected boolean`	`startReadFromWaitingReader()`
`protected boolean`	`startWrite()`
`protected boolean`	`startWriteFromNewWriter()`
`protected boolean`	`startWriteFromWaitingWriter()`
`Sync`	`writeLock()`	get the writeLock *

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

activeReaders_
```
protected long activeReaders_
```

activeWriter_

protected java.lang.Thread activeWriter_

waitingReaders_
```
protected long waitingReaders_
```

waitingWriters_
```
protected long waitingWriters_
```

readerLock_

protected final WriterPreferenceReadWriteLock.ReaderLock readerLock_

writerLock_

protected final WriterPreferenceReadWriteLock.WriterLock writerLock_

Constructor Detail
- WriterPreferenceReadWriteLock
```
public WriterPreferenceReadWriteLock()
```

Method Detail
- writeLock
```
public Sync writeLock()
```
  Description copied from interface: ReadWriteLock
  
  get the writeLock *
  
  Specified by:
  
  writeLock in interface ReadWriteLock
- readLock
```
public Sync readLock()
```
  Description copied from interface: ReadWriteLock
  
  get the readLock *
  
  Specified by:
  
  readLock in interface ReadWriteLock
- cancelledWaitingReader
```
protected void cancelledWaitingReader()
```
- cancelledWaitingWriter
```
protected void cancelledWaitingWriter()
```
- allowReader
```
protected boolean allowReader()
```
  Override this method to change to reader preference *
- startRead
```
protected boolean startRead()
```
- startWrite
```
protected boolean startWrite()
```
- startReadFromNewReader
```
protected boolean startReadFromNewReader()
```
- startWriteFromNewWriter
```
protected boolean startWriteFromNewWriter()
```
- startReadFromWaitingReader
```
protected boolean startReadFromWaitingReader()
```
- startWriteFromWaitingWriter
```
protected boolean startWriteFromWaitingWriter()
```
- endRead
```
protected WriterPreferenceReadWriteLock.Signaller endRead()
```
  Called upon termination of a read. Returns the object to signal to wake up a waiter, or null if no such
- endWrite
```
protected WriterPreferenceReadWriteLock.Signaller endWrite()
```
  Called upon termination of a write. Returns the object to signal to wake up a waiter, or null if no such