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

[Jon Masamitsu]

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 is_metaspace_object 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::is_valid_method)
>
> open webrev at http://cr.openjdk.java.net/~coleenp/8029178/
> bug link https://bugs.openjdk.java.net/browse/JDK-8029178
>
> Thanks,
> Coleen