[$] A perf ABI fix
It is often said that the kernel developers are committed to avoiding ABI
breaks at almost any cost. But ABI problems can, at times, be hard to
avoid. Some have argued that the perf events interface is particularly
subject to incompatible ABI changes because the perf tool is part
of the
kernel tree itself; since perf can evolve with the kernel, there
is a possibility that
developers might not even notice a break. So the recent discovery of a
perf ABI issue is worth looking at as an
example of how compatibility problems are handled in that code.