Abstract. Atomicsectionscanbeimplementedusinglockinference. For lock inference to be practically useful, it is crucial that large libraries be analysed. However, libraries are challenging for static analysis, due to their cyclomatic complexity. Existing approaches either ignore libraries, require library implementers to annotate which locks to take or only consider accesses performed upto one level deep in library call chains. Thus, some library accesses may go unprotected, leading to atomicity violations that atomic sections are supposed to eliminate. We presentalock inference approach for Javathatanalyses library methods in full. We achieve this by (i) formulating lock inference as an Interprocedural Distributive Environment dataflow problem, (ii) using a graph representation for summary information and (iii) applying a number of optimisations to our implementation to reduce space-time requirements and locks inferred. We demonstrate the scalability of our approach by analysing the entire GNU Classpath library comprising 122KLOC.