RFR (XS) 8047212: fix race between ObjectMonitor alloc and verification code (original) (raw)
Daniel D. Daugherty daniel.daugherty at oracle.com
Tue Oct 20 21:15:12 UTC 2015
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Greetings,
I've updated the fix based on feedback from Carsten V and David H.
Webrev URL: http://cr.openjdk.java.net/~dcubed/8047212-webrev/1-jdk9-hs-rt/
Changes relative to round 0:
- only src/share/vm/runtime/synchronizer.cpp has changed
- reads of gBlockList now use OrderAccess::load_ptr_acquire()
code style cleanups:
- only cleaned up the functions that I touched to make the OrderAccess::load_ptr_acquire() changes
- changed implied booleans into real boolean expressions
- moved some locals to narrower context
- added/removed some blank lines
- made casts consistent with the majority style in this file
I'm repeating all of the same testing that I did for round 0. The round 1 bits have not yet made it through JPRT-west, but the jobs are mostly done.
Thanks, in advance, for any comments, questions or suggestions.
Dan
On 10/19/15, 9:02 PM, Daniel D. Daugherty wrote:
Greetings,
I have a fix for a long standing race between the lock-free ObjectMonitor verification code and the normal (locked) ObjectMonitor block allocation code path. For this fix, I would like at least a Runtime team reviewer and a Serviceability team reviewer. Thanks! JDK-8047212 runtime/ParallelClassLoading/bootstrap/random/inner-complex assert(ObjectSynchronizer::verifyobjmonisinpool(inf)) failed: monitor is invalid https://bugs.openjdk.java.net/browse/JDK-8047212 Webrev URL: http://cr.openjdk.java.net/~dcubed/8047212-webrev/0-jdk9-hs-rt/ Testing: Aurora Adhoc RT-SVC nightly batch 4 inner-complex fastdebug parallel runs for 4+ days and 600K iterations without seeing this failure; the experiment is still running; final results to be reported at the end of the review cycle JPRT -testset hotspot This fix: - makes ObjectMonitor::gBlockList volatile - uses "OrderAccess::releasestoreptr(&gBlockList, temp)" to make sure the new block updates happen before gBlockList is changed to refer to the new block - add SA support for a "static pointer volatile" field like: static ObjectMonitor * volatile gBlockList; See the following link for a nice description of what "volatile" means in the different positions on a variable/parameter decl line: http://www.embedded.com/electronics-blogs/beginner-s-corner/4023801/Introduction-to-the-Volatile-Keyword
Thanks, in advance, for any comments, questions or suggestions. Dan
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