PK99787; 6.1.0.27: dynacache clear causes dead lock

Download Description

PK99787 resolves the following problem:

ERROR DESCRIPTION:
After approximately 36 hours running, an internal test case died because all WebContainer threads were hanging. Analyzing the threaddump showed a deadlock of two threads which blocked all other WebContainer threads.

These are the stacktraces:

Thread Name WebContainer : 1057
State Deadlock/Blocked
Monitor Owns Monitor Lock on
com/ibm/ws/cache/Cache@00007FFD04508B60/00007FFD04508B78
Waiting for Monitor Lock on
com/ibm/ws/cache/Cache@00007FFD05715A88/00007FFD05715AA0
Java Stack at
com/ibm/ws/cache/Cache.batchUpdate(Cache.java:1274(Compiled
Code))
at com/ibm/ws/cache/BatchUpdateDaemon.wakeUp(Batch
UpdateDaemon.java:353(Compiled Code))
at com/ibm/ws/cache/BatchUpdateDaemon.cache
Command_Clear(BatchUpdateDaemon.java:108(Compiled Code))
at com/ibm/ws/cache/Cache.clear(Cache.java:1581(Compiled Code))


Thread Name WebContainer : 1125
State Deadlock/Blocked
Monitor Owns Monitor Lock on
com/ibm/ws/cache/Cache@00007FFD05715A88/00007FFD05715AA0
Waiting for Monitor Lock on
com/ibm/ws/cache/Cache@00007FFD04508B60/00007FFD04508B78
Java Stack at
com/ibm/ws/cache/Cache.batchUpdate(Cache.java:1259(Compiled
Code))
at com/ibm/ws/cache/BatchUpdateDaemon.wakeUp(Batch
UpdateDaemon.java:353(Compiled Code))
at com/ibm/ws/cache/BatchUpdateDaemon.cache
Command_Clear(BatchUpdateDaemon.java:108(Compiled Code))
at com/ibm/ws/cache/Cache.clear(Cache.java:1581(Compiled Code))

LOCAL FIX:
None

PROBLEM SUMMARY

USERS AFFECTED:
All users of IBM WebSphere Application Server V6.1 and V7.0 using dynacache.

PROBLEM DESCRIPTION:
Performance of dynacache clear operations in high volume environments deadlocks.

RECOMMENDATION:
None

In order to protect the cache instance dynacache uses synchronized methods to allow synchronous access to clear operations. This synchronization is excessive and may cause a deadlock during a stress situation.

PROBLEM CONCLUSION:
Excessive synchronization has been eliminated to allow clear operations to perform without a deadlock.

The fix for this APAR is currently targeted for inclusion in Fix Packs 6.1.0.33 and 7.0.0.9. Refer to the Recommended Updates page for delivery information:
http://www.ibm.com/support/docview.wss?uid=swg27004980

Change History
Last Updated: 13 May 2010

• 13 May 2010: Added additional iFix for 6.1.0.31