BUG/MEDIUM: memory_pool: Update the seq number in pool_flush().

In pool_flush(), we can't just set the free_list to NULL, or we may suffer
the ABA problem. Instead, use a double-width CAS and update the sequence
number.

This should be backported to 2.1, 2.0 and 1.9.
This may, or may not, be related to github issue #476.
1 file changed