On Saturday, 12 October 2013 at 06:16:24 UTC, Rainer Schuetze
wrote:
in pseudo-assembly missing null-checks:
Thread1 (R = P) Thread2 (S = R)
mov ecx,[R]
; thread suspended
You need an sequentially consistent write. You also need to
increment the refcount BEFORE ! This codegen is incorrect.
mov eax,[P]
inc [eax].refcnt
Same here.
mov ebx,[R]
mov [R],eax
dec [ebx].refcnt ; refcnt of O now 0
jnz done
call delete_ebx
; thread resumed
inc [ecx].refcnt
done:
The increment on [ecx].refcnt modifies garbage.
This can be done atomically (even with eventually consistent
increment, don't need full sequential consistency here, you still
need fully sequential consistent decrement).
