[GitHub] [geode] agingade commented on a change in pull request #5823: GEODE-8771: invalidate should acquire the lock before initIndex

[GitBox <gi...@apache.org>]

agingade commented on a change in pull request #5823:
URL: https://github.com/apache/geode/pull/5823#discussion_r539645325



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File path: geode-core/src/main/java/org/apache/geode/internal/cache/AbstractRegionMap.java
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@@ -1282,14 +1282,18 @@ public boolean invalidate(EntryEventImpl event, boolean invokeCallbacks, boolean
     DiskRegion dr = owner.getDiskRegion();
     boolean ownerIsInitialized = owner.isInitialized();
 
+    // lock before waitForIndexInit so that we should wait
+    // till a concurrent clear to finish
+    lockForCacheModification(owner, event);

Review comment:
       @jchen21 
   There is locking mechanism to co-ordinate between cache modification (index maintenance) and index initialization. During index initialization all the cache operations are blocked.
   As part of index management; clear invokes index re-initialization. 
   Also, during clear no cache operations are allowed; this is co-ordinated through lockForCacheModification (version lock).
   The hang is observed due to:
   Thread1 calling update, which blocks index initialization.
   Thread2 calling clear, takes the cache modification lock, this blocks all cache operation; and clear triggers index re-initialization; this is now blocked for thread1 to finish update. But thread1 is waiting for cache modification lock which is held by thread2; resulting in dead-lock.
   
   




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