RFR(S): 8035841: assert(dp_src->tag() == dp_dst->tag()) failed: should be same tags 1 != 0 at ciMethodData.cpp:90

[Roland Westrelin]

In ciMethodData.cpp: when the ciMethodData is loaded, the code walks over the traps in the extra data to translate their Method into a ciMethod. There can be new traps added as this is happening so the code that walks over the traps should iterate over the ciMethodData copy of the profile data. Because of concurrent updates, the assert is incorrect.

In methodData.cpp: I had to remove the asserts because they are incorrect in case of concurrent updates as well. Also, the test that checks whether there is room for a speculative trap is broken in case of concurrent updates: the intent of next_extra(dp) is to check the next cell but if dp is allocated to a speculative trap concurrently it checks 2 cells from the current cell. Also, next_extra(dp)->tag() != DataLayout::no_tag doesn’t mean there’s no more space because it may have been allocated to some other trap concurrently and there may be more free space after.

http://cr.openjdk.java.net/~roland/8035841/webrev.00/

Roland.