8212205 (XS) VM asserts after CDS archive has been unmapped (original) (raw)

Harold David Seigel harold.seigel at oracle.com
Thu Oct 25 18:34:28 UTC 2018

HI Ioi,

This looks good.

What regression tests were run?

Thanks, Harold

On 10/25/2018 2:22 PM, Ioi Lam wrote:

https://bugs.openjdk.java.net/browse/JDK-8212205 http://cr.openjdk.java.net/~iklam/jdk12/8212205-crash-after-cds-unmap.v01/

This is a silly bug but it happens only rarely, when address space randomization causes insufficient memory to be reservable at addresses required by CDS. In this case, the CDS archive is unmapped, but we forget to clean up sharedmetaspace{base,top}. As a result, the JVM will misidentify metaspace objects allocated in certain address ranges to be "shared", in the following function: class MetaspaceObj { bool isshared() const { return (((void*)this) < sharedmetaspacetop && ((void*)this) >= sharedmetaspacebase); } } The fix is to reset those pointers after CDS has been unmapped. Thanks - Ioi

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