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クラス org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock

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説明

Reader/Writer lock with write priority.

If a reader holds the lock, all incoming readers are allowed to acquire the lock until a write arrives. A writer must wait for all current readers to release the lock before acquiring it.
When a writer has the lock, everybody else is blocked.
When a writer release the lock, there is a writer priority so if another writer is waiting it will have the lock even if it arrived later than readers. Writers are prioritary against readers but all writers get the lock in a FIFO order.

作者:
Emmanuel Cecchet
バージョン:
1.0

ReadPrioritaryFIFOWriteLock.java の 44 行で定義されています。

Public メソッド

 ReadPrioritaryFIFOWriteLock ()
void acquireRead () throws InterruptedException
synchronized void releaseRead ()
void acquireWrite () throws InterruptedException
synchronized void releaseWrite ()
final synchronized boolean isReadLocked ()
final synchronized boolean isWriteLocked ()

Private 変数

int activeReaders
boolean activeWriter
int waitingReaders
int waitingWriters
Object readSync
ArrayList writeWaitingQueue

コンストラクタとデストラクタ

org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.ReadPrioritaryFIFOWriteLock (   ) 
 

Creates a new ReadPrioritaryFIFOWriteLock instance. ReadPrioritaryFIFOWriteLock.java の 64 行で定義されています。

参照先 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeReaders, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeWriter, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.readSync, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.waitingReaders, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.waitingWriters, と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.writeWaitingQueue.

00065   {
00066     activeReaders = 0;
00067     activeWriter = false;
00068     waitingReaders = 0;
00069     waitingWriters = 0;
00070     readSync = new Object();
00071     writeWaitingQueue = new ArrayList();
00072   }

メソッド

void org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireRead (   )  throws InterruptedException
 

Acquires the lock for a read.

例外:
InterruptedException if wait failed (the lock should remain in a correct state)
ReadPrioritaryFIFOWriteLock.java の 80 行で定義されています。

参照先 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeReaders, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeWriter, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.readSync, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.waitingReaders, と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.waitingWriters.

00081   {
00082     synchronized (this)
00083     {
00084       if ((waitingWriters == 0) && !activeWriter)
00085       { // No active or pending writer
00086         activeReaders++;
00087         return;
00088       }
00089     }
00090 
00091     // Beyond this point, we have to wait
00092     synchronized (readSync)
00093     {
00094       // It becomes a little bit tricky here but a writer could have
00095       // released the lock between the first test at the beginning of
00096       // this function and this point. Therefore we have to recheck if
00097       // the lock is not completely idle else we'll never wake up !
00098       synchronized (this)
00099       {
00100         if (!activeWriter)
00101         { // No active or pending writer
00102           activeReaders++;
00103           return;
00104         }
00105       }
00106 
00107       waitingReaders++;
00108       try
00109       {
00110         readSync.wait();
00111       }
00112       catch (InterruptedException ie)
00113       {
00114         waitingReaders--; // roll back state
00115         throw ie;
00116       }
00117       waitingReaders--;
00118     }
00119     synchronized (this)
00120     {
00121       activeReaders++;
00122     }
00123   }

void org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireWrite (   )  throws InterruptedException
 

Acquires the lock for a write.

例外:
InterruptedException if wait failed (the lock should remain in a correct state)
ReadPrioritaryFIFOWriteLock.java の 149 行で定義されています。

参照先 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeReaders, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeWriter, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseWrite(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.waitingWriters, と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.writeWaitingQueue.

参照元 org.objectweb.cjdbc.controller.loadbalancer.raidb2.RAIDb2ec.disableBackend(), org.objectweb.cjdbc.controller.loadbalancer.raidb1.RAIDb1ec.disableBackend(), org.objectweb.cjdbc.controller.loadbalancer.raidb2.RAIDb2ec.enableBackend(), と org.objectweb.cjdbc.controller.loadbalancer.raidb1.RAIDb1ec.enableBackend().

00150   {
00151     synchronized (Thread.currentThread())
00152     {
00153       synchronized (this)
00154       {
00155         if ((activeReaders == 0) && !activeWriter)
00156         {
00157           activeWriter = true;
00158           return;
00159         }
00160         else
00161         {
00162           waitingWriters++;
00163           writeWaitingQueue.add(Thread.currentThread());
00164         }
00165       }
00166       try
00167       {
00168         Thread.currentThread().wait();
00169       }
00170       catch (InterruptedException ie)
00171       {
00172         releaseWrite();
00173         throw ie;
00174       }
00175     }
00176   }

final synchronized boolean org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.isReadLocked (   ) 
 

Tests if the lock is currently held by at least one reader.

戻り値:
true if the lock is held by a reader
ReadPrioritaryFIFOWriteLock.java の 211 行で定義されています。

参照先 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeReaders.

00212   {
00213     return activeReaders > 0;
00214   }

final synchronized boolean org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.isWriteLocked (   ) 
 

Tests if the lock is currently held by a writer.

戻り値:
true if the lock is held by a writer
ReadPrioritaryFIFOWriteLock.java の 221 行で定義されています。

参照先 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeWriter.

00222   {
00223     return activeWriter;
00224   }

synchronized void org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseRead (   ) 
 

Releases a lock previously acquired for reading. ReadPrioritaryFIFOWriteLock.java の 128 行で定義されています。

参照先 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeReaders, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeWriter, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.waitingWriters, と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.writeWaitingQueue.

00129   {
00130     activeReaders--;
00131     if ((activeReaders == 0) && (waitingWriters > 0))
00132     { // Wake up first waiting write if any
00133       Object ww = writeWaitingQueue.remove(0);
00134       synchronized (ww)
00135       {
00136         ww.notify();
00137         activeWriter = true;
00138         waitingWriters--;
00139       }
00140     }
00141   }

synchronized void org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseWrite (   ) 
 

Releases a lock previously acquired for writing. ReadPrioritaryFIFOWriteLock.java の 181 行で定義されています。

参照先 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeWriter, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.readSync, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.waitingReaders, org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.waitingWriters, と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.writeWaitingQueue.

参照元 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireWrite(), org.objectweb.cjdbc.controller.loadbalancer.raidb2.RAIDb2ec.disableBackend(), org.objectweb.cjdbc.controller.loadbalancer.raidb1.RAIDb1ec.disableBackend(), org.objectweb.cjdbc.controller.loadbalancer.raidb2.RAIDb2ec.enableBackend(), と org.objectweb.cjdbc.controller.loadbalancer.raidb1.RAIDb1ec.enableBackend().

00182   {
00183     activeWriter = false;
00184 
00185     // Writer priority
00186     if (waitingWriters > 0)
00187     { // Wake up first waiting write if any
00188       Object ww = writeWaitingQueue.remove(0);
00189       synchronized (ww)
00190       {
00191         ww.notify();
00192         activeWriter = true;
00193         waitingWriters--;
00194       }
00195     }
00196 
00197     // Wake up readers
00198     else
00199       synchronized (readSync)
00200       {
00201         if (waitingReaders > 0)
00202           readSync.notifyAll();
00203       }
00204   }

変数

int org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeReaders [private]
 

Threads executing read. ReadPrioritaryFIFOWriteLock.java の 47 行で定義されています。

参照元 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireRead(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireWrite(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.isReadLocked(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.ReadPrioritaryFIFOWriteLock(), と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseRead().

boolean org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.activeWriter [private]
 

Is there an active writer? ReadPrioritaryFIFOWriteLock.java の 50 行で定義されています。

参照元 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireRead(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireWrite(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.isWriteLocked(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.ReadPrioritaryFIFOWriteLock(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseRead(), と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseWrite().

Object org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.readSync [private]
 

ReadPrioritaryFIFOWriteLock.java の 58 行で定義されています。

参照元 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireRead(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.ReadPrioritaryFIFOWriteLock(), と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseWrite().

int org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.waitingReaders [private]
 

Threads not yet in read. ReadPrioritaryFIFOWriteLock.java の 53 行で定義されています。

参照元 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireRead(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.ReadPrioritaryFIFOWriteLock(), と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseWrite().

int org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.waitingWriters [private]
 

Threads not yet in write. ReadPrioritaryFIFOWriteLock.java の 56 行で定義されています。

参照元 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireRead(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireWrite(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.ReadPrioritaryFIFOWriteLock(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseRead(), と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseWrite().

ArrayList org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.writeWaitingQueue [private]
 

ReadPrioritaryFIFOWriteLock.java の 59 行で定義されています。

参照元 org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.acquireWrite(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.ReadPrioritaryFIFOWriteLock(), org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseRead(), と org.objectweb.cjdbc.common.util.ReadPrioritaryFIFOWriteLock.releaseWrite().

このクラスの説明は次のファイルから生成されました:
CJDBCversion1.0.4に対してTue Oct 12 15:16:19 2004に生成されました。 doxygen 1.3.8