Lock Order

NOTE(LOCK_ORDER(LockNameList))

This annotation, which is allowed either outside or inside a function definition, specifies the order in which locks should be acquired. It is similar to the assert order and order subcommands. See Appendix A, LockLint Command Reference.

To avoid deadlocks, LockLint assumes that whenever multiple locks must be held at once they are always acquired in a well-known order. If LockLint has been informed of such ordering using this annotation, an informative message is produced whenever the order is violated.

This annotation may be used multiple times, and the semantics will be combined appropriately. For example, given the annotations

NOTE(LOCK_ORDER(a b c))

NOTE(LOCK_ORDER(b d))

LockLint will deduce the ordering:

NOTE(LOCK_ORDER(a d))

It is not possible to deduce anything about the order of c with respect to d in this example.

If a cycle exists in the ordering, an appropriate error message will be generated.