Managing instructions on a processor includes: executing threads having access to a stored library of operations. For a first thread executing on the first processor core, for each instruction included in the first thread and identified as being associated with a lock operation corresponding to a particular lock, the managing includes determining if the particular lock has already been acquired for another thread executing on a processor core other than the first processor core, and if so, continuing to perform the lock operation for multiple attempts using a hardware lock operation different from the lock operation in the stored library, and if not, acquiring the particular lock for the first thread. The hardware lock operation performs a modified atomic operation that changes a result of the hardware lock operation for failed attempts to acquire the particular lock relative to a result of the lock operation in the stored library.