RFR 8029178: Parallel class loading test anonymous-simple gets SIGSEGV in Metaspace:,:contains (original) (raw)

Jon Masamitsu jon.masamitsu at oracle.com
Fri Jan 3 10:09:38 PST 2014

Coleen,

http://cr.openjdk.java.net/~coleenp/8029178/src/share/vm/memory/metachunk.hpp.frames.html

146 bool contains(const void* ptr) { return bottom() < ptr && ptr <= _top; }

I think bottom() points to the first chunk. Also _top points to the start of the unallocated space (next place where a chunk will be allocated). So I would think this should be

bool contains(const void* ptr) { return bottom() <=ptr && ptr < _top; }

http://cr.openjdk.java.net/~coleenp/8029178/src/share/vm/memory/metaspace.cpp.frames.html

Don't you need some locking to protect the "chunks_in_use()" lists?

2382 bool SpaceManager::contains(const void *ptr) { 2383 for (ChunkIndex i = ZeroIndex; i < NumberOfInUseLists; i = next_chunk_index(i)) 2384 { 2385 Metachunk* curr = chunks_in_use(i); 2386 while (curr != NULL) { 2387 if (curr->contains(ptr)) return true; 2388 curr = curr->next(); 2389 } 2390 } 2391 return false; 2392 } 2393

Jon

On 1/2/2014 9:25 AM, Coleen Phillmore wrote:

Summary: Metaspace::contains cannot look at purged metaspaces while CMS concurrently deallocates them.

Removed 2 calls to ismetaspaceobject where the object may be in a deallocated metaspace. Removed walking virtual space lists for determining contains because the virtual space list can change concurrently with the walk. CLDG::contains is slower but no slowdowns with testing were observed. Tested by SQE testbase tests, jtreg tests. Functional testing by parallel class loading tests and nsk/coverage/arguments/arguments008 (ie. calls Method::isvalidmethod) open webrev at http://cr.openjdk.java.net/~coleenp/8029178/ bug link https://bugs.openjdk.java.net/browse/JDK-8029178 Thanks, Coleen

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