libyang  2.0.194
libyang is YANG data modelling language parser and toolkit written (and providing API) in C.
Threading Limitations

Context

It is safe to read from ly_ctx structure concurrently and use its dictionary, which is protected by a lock. Thread-safe functions include any ones working with data trees (only context dictionary is accessed) and all the ly_ctx_get_*() functions. Generally, they are the functions with const context parameter.

Data Trees

Data trees are not internally synchronized so the general safe practice of a single writer or several concurrent readers should be followed. Specifically, only the functions with non-const lyd_node parameters modify the node(s) and no concurrent execution of such functions should be allowed on a single data tree or subtrees of one.