Wiktor N created JCS-144:
----------------------------
Summary: BlockDiskCache hangs on SEVERE: Region [TMS] Failure
getting from disk--IOException
Key: JCS-144
URL: https://issues.apache.org/jira/browse/JCS-144
Project: Commons JCS
Issue Type: Bug
Components: Indexed Disk Cache
Affects Versions: jcs-2.0-alpha-2
Environment: version 1.7.0_75, vendor Oracle Corporation
Reporter: Wiktor N
If I get a failure reading an object from cache, the thread locks, with
following stack trace:
"AWT-EventQueue-0" prio=6 tid=0x00000000112aa000 nid=0x1444 waiting on
condition [0x0000000013dc9000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000007cbf84b00> (a
java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:867)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1197)
at
java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock(ReentrantReadWriteLock.java:945)
at
org.apache.commons.jcs.auxiliary.disk.block.BlockDiskCache.reset(BlockDiskCache.java:643)
at
org.apache.commons.jcs.auxiliary.disk.block.BlockDiskCache.processGet(BlockDiskCache.java:343)
at
org.apache.commons.jcs.auxiliary.AbstractAuxiliaryCacheEventLogging.getWithEventLogging(AbstractAuxiliaryCacheEventLogging.java:109)
at
org.apache.commons.jcs.auxiliary.disk.AbstractDiskCache.doGet(AbstractDiskCache.java:771)
at
org.apache.commons.jcs.auxiliary.disk.AbstractDiskCache.get(AbstractDiskCache.java:279)
at
org.apache.commons.jcs.engine.control.CompositeCache.get(CompositeCache.java:550)
- locked <0x00000007cbf62c00> (a
org.apache.commons.jcs.engine.control.CompositeCache)
at
org.apache.commons.jcs.engine.control.CompositeCache.get(CompositeCache.java:455)
at
org.apache.commons.jcs.access.CacheAccess.getCacheElement(CacheAccess.java:125)
Looing at the code in BlockDiskCache I see, that we first acquire read lock in
processGet, and then try to acquire write lock in reset(). According to API
spec:
http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/locks/ReentrantReadWriteLock.html
It is unsupported to upgrade an lock from read to write ("Additionally, a
writer can acquire the read lock, but not vice-versa").
Either read lock should be dropped early on exception or different lock
mechanism should be used
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