Howard Chu authored Jan 27, 2015 and Quanah Gibson-Mount committed Jan 27, 2015

Remove assert. This is merely a cache of parent DNs, failure to
insert doesn't affect outcome.

Copied from 58ddb552.

Leonid Yuriev authored Oct 17, 2014 and Hallvard Furuseth committed Jan 14, 2015

Inconsistent reading & SIGSEGV due to the race condition.

Leonid Yuriev authored Oct 17, 2014 and Hallvard Furuseth committed Jan 14, 2015

Globally shared fields of meta-data were not 'volatile'.
Code from 9a80a8a8,
except the unportable __synchronize().