On 29/11/2023 06:02, Ian Rogers wrote: > perf_cpu_map__nr's behavior around an empty CPU map is strange as it > returns that there is 1 CPU. Changing code that may rely on this > behavior is hard, we can at least document the behavior. > > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx> > --- > tools/lib/perf/include/perf/cpumap.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/tools/lib/perf/include/perf/cpumap.h b/tools/lib/perf/include/perf/cpumap.h > index 523e4348fc96..90457d17fb2f 100644 > --- a/tools/lib/perf/include/perf/cpumap.h > +++ b/tools/lib/perf/include/perf/cpumap.h > @@ -44,7 +44,18 @@ LIBPERF_API struct perf_cpu_map *perf_cpu_map__merge(struct perf_cpu_map *orig, > LIBPERF_API struct perf_cpu_map *perf_cpu_map__intersect(struct perf_cpu_map *orig, > struct perf_cpu_map *other); > LIBPERF_API void perf_cpu_map__put(struct perf_cpu_map *map); > +/** > + * perf_cpu_map__cpu - get the CPU value at the given index. Returns -1 if index > + * is invalid. > + */ > LIBPERF_API struct perf_cpu perf_cpu_map__cpu(const struct perf_cpu_map *cpus, int idx); > +/** > + * perf_cpu_map__nr - for an empty map returns 1, as perf_cpu_map__cpu returns a > + * cpu of -1 for an invalid index, this makes an empty map > + * look like it contains the "any CPU"/dummy value. Otherwise > + * the result is the number CPUs in the map plus one if the > + * "any CPU"/dummy value is present. Hmmm... I'm not sure whether to laugh or cry at that API. Reviewed-by: James Clark <james.clark@xxxxxxx> > + */ > LIBPERF_API int perf_cpu_map__nr(const struct perf_cpu_map *cpus); > /** > * perf_cpu_map__has_any_cpu_or_is_empty - is map either empty or has the "any CPU"/dummy value.
