RFR (XS) 8047212: fix race between ObjectMonitor alloc and verification code (original) (raw)
Carsten Varming varming at gmail.com
Tue Oct 20 04:09:44 UTC 2015
- Previous message: RFR (XS) 8047212: fix race between ObjectMonitor alloc and verification code
- Next message: RFR (XS) 8047212: fix race between ObjectMonitor alloc and verification code
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
Dear Dan,
I thought acquire/release semantics mandated that the release should be paired with an acquire. In this case, the first line in verify_objmon_isinpool should be changed from "PaddedEnd * block = (PaddedEnd *)gBlockList" to use a load_acquire. Actually, it seems like there are a lot of reads of gBlockList that should be replaced with a load_acquire in synchronizer.cpp.
Otherwise the change looks great.
Carsten (not a reviewer).
On Mon, Oct 19, 2015 at 8:02 PM, Daniel D. Daugherty < daniel.daugherty at oracle.com> 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
- Previous message: RFR (XS) 8047212: fix race between ObjectMonitor alloc and verification code
- Next message: RFR (XS) 8047212: fix race between ObjectMonitor alloc and verification code
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]