The call cache changes when the call site becomes polymophic and can
result in the generated code falsely assuming cd->cc->cme is not NULL.
Here is a crasher:
def body(thing)
thing.strip
end
str = ""
10.times { body(str) }
body(0) rescue p 'not found'
body(str)
opt_send_without_block needs it. Ideally we would use this example
only when an instruction in the compiled sequence needs `ec`. We can
worry about that later.
To reduce the number of locking for encoding manipulation,
enc_table::list is splited to ::default_list and ::additional_list.
::default_list is pre-allocated and no need locking to access to
the ::default_list. If additional encoding space is needed, use
::additional_list and this list need to use locking.
However, most of case, ::default_list is enough.
According to the log of ac803ab55d, I
found that a thread terminates silently due to "recycled object" of
id2ref:
```
"/home/chkbuild/chkbuild/tmp/build/20201017T033002Z/ruby/lib/drb/drb.rb:366:in `_id2ref'"
"/home/chkbuild/chkbuild/tmp/build/20201017T033002Z/ruby/lib/drb/drb.rb:366:in `to_obj'"
"/home/chkbuild/chkbuild/tmp/build/20201017T033002Z/ruby/lib/drb/drb.rb:1528:in `to_obj'"
"/home/chkbuild/chkbuild/tmp/build/20201017T033002Z/ruby/lib/drb/drb.rb:1847:in `to_obj'"
"/home/chkbuild/chkbuild/tmp/build/20201017T033002Z/ruby/lib/drb/drb.rb:1136:in `method_missing'"
"/home/chkbuild/chkbuild/tmp/build/20201017T033002Z/ruby/test/rinda/test_rinda.rb:652:in `block in do_reply'"
```
https://rubyci.org/logs/rubyci.s3.amazonaws.com/rhel8/ruby-master/log/20201017T033002Z.log.html.gz
I believe that this unintentional thread termination has caused
intermittent timeout failure of `TestRingServer#test_do_reply`.
The root cause of the "recycled object" issue is a bug of
`TestRingServer#test_do_reply`. It creates a callback Proc object but
does not hold the reference to the object:
```
callback = DRb::DRbObject.new callback
```
The original "callback" object is GC'ed unintentionally.
I could consistently reproduce this issue on my machine by adding
`GC.stress = true` at the first of `_test_do_reply` method body.
This change uses another local variable name, "callback_orig", to keep
the original Proc object.
iv_index_tbl manages instance variable indexes (ID -> index).
This data structure should be synchronized with other ractors
so introduce some VM locks.
This patch also introduced atomic ivar cache used by
set/getinlinecache instructions. To make updating ivar cache (IVC),
we changed iv_index_tbl data structure to manage (ID -> entry)
and an entry points serial and index. IVC points to this entry so
that cache update becomes atomically.
Buggy native extensions could have mark functions that cause stack
overflow. When a stack overflow happens during GC, Ruby used to recover
by raising an exception, which runs the interpreter. It's not safe to
run the interpreter during GC since the GC is in an inconsistent state.
This could cause object allocation during GC, for example.
Instead of running the interpreter and potentially causing a crash down
the line, fail fast and abort.
