IssueTracker

Android's ConcurrentHashMap in API level 21 / 22 has the same problem that was detected in the OpenJDK Java 8 ea builds before b120 (it was fixed in b120 in Dec. 2013).


Please refer to the OpenJKD bug description


https://bugs.openjdk.java.net/browse/JDK-8028564

and

http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jdk7/java/util/concurrent/ConcurrentHashMap.java?r1=1.35&r2=1.36



Basically, multithreaded put(), putIfAbsent(), putAll(), ... operations can fail to add a key/value pair if there are hash collisions on the added keys and the underlying datastructure needs to be resized at the time of the concurrent puts.

This is no wonder since Android API 21/22 uses the same CHM implementation that was used until OpenJDK 8 ea b120 (where the bug was fixed).


I could reproduce this bug on both API 21 and API 22 on a TrekStor SurfTab xintron i 7.0 (Intel st70408_4_coho). Fortunately it is quite easy to reproduce, using eiher the test that is provided in the JDK-8028564 link or the quite similar ConcurrentAssociateTest that was added as regression test. Both tests use Java 8 APIs, but it should be straightforward to do without on Android.

My version of the test (attached) closely follows the original ConcurrentAssociateTest, but you'd have to use a 3rd party library that emulates the Java 8 API to run it: https://sourceforge.net/projects/streamsupport/


Note that I'll be away on leave from tomorrow so I won't be able to respond to furter inquiry for the next 10 days.