RFR: 8175010: ImageReader is not thread-safe

Claes Redestad claes.redestad at oracle.com
Wed Feb 15 13:22:17 UTC 2017


a few intermittent but rare test failures[1] that has appeared
since the latest jake integration, and since one of the changes
in there was to make initialization of the system ImageReader
lazy there appears to be cases where ImageReaders are not
safely published:

- Ensure ImageReader::open is called only once per Path in
ImageReaderFactory by using CHM.computeIfAbsent
- Ensure ImageReader.reader is safely published to a
final field and signal close using a volatile boolean instead

webrev: http://cr.openjdk.java.net/~redestad/8175010/webrev.02/
bug: https://bugs.openjdk.java.net/browse/JDK-8175010

Testing shows no issues (which admittedly doesn't mean we're
actually solving the root cause for JDK-8174817), and performance
numbers from adding a volatile read indicate that any overhead
is lost in the noise on ImageReader-heavy workloads.



[1] https://bugs.openjdk.java.net/browse/JDK-8174817

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