Tries to become the owner of the specified context,
as with MainContext.acquire. But if another thread
is the owner, atomically drop mutex and wait on cond until
that owner releases ownership or until cond is signaled, then
try again (once) to become the owner.
Tries to become the owner of the specified context, as with MainContext.acquire. But if another thread is the owner, atomically drop mutex and wait on cond until that owner releases ownership or until cond is signaled, then try again (once) to become the owner.