memory conditions. Without this fix a DNS cache DB or
ADB could incorrectly stay in an over memory state,
effectively refusing further caching, which
subsequently made a BIND 9 caching server unworkable.
This fix prevents this problem from happening by
polling the state of the memory context, rather than
making a copy of the state, which appeared to cause
a race. This is a "workaround" in that it doesn't
solve the possible race per se, but several experiments
proved this change solves the symptom. Also, the
polling overhead hasn't been reported to be an issue.
This bug should only affect a caching server that
specifies a finite max-cache-size. It's also quite
likely that the bug happens only when enabling threads,
but it's not confirmed yet. [RT #21818]
85b94d05c0