Allow computation of thread map index from a PID. Note, with a
perf_cpu_map the sorted nature allows for a binary search to compute
the index which isn't currently possible with a perf_thread_map as
they aren't guaranteed sorted.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/lib/perf/include/perf/threadmap.h |  1 +
 tools/lib/perf/threadmap.c              | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/tools/lib/perf/include/perf/threadmap.h b/tools/lib/perf/include/perf/threadmap.h
index 8b40e7777cea..44deb815b817 100644
--- a/tools/lib/perf/include/perf/threadmap.h
+++ b/tools/lib/perf/include/perf/threadmap.h
@@ -14,6 +14,7 @@ LIBPERF_API void perf_thread_map__set_pid(struct perf_thread_map *map, int idx,
 LIBPERF_API char *perf_thread_map__comm(struct perf_thread_map *map, int idx);
 LIBPERF_API int perf_thread_map__nr(struct perf_thread_map *threads);
 LIBPERF_API pid_t perf_thread_map__pid(struct perf_thread_map *map, int idx);
+LIBPERF_API int perf_thread_map__idx(struct perf_thread_map *map, pid_t pid);
 
 LIBPERF_API struct perf_thread_map *perf_thread_map__get(struct perf_thread_map *map);
 LIBPERF_API void perf_thread_map__put(struct perf_thread_map *map);
diff --git a/tools/lib/perf/threadmap.c b/tools/lib/perf/threadmap.c
index 3ca9ba4987fc..db431b036f57 100644
--- a/tools/lib/perf/threadmap.c
+++ b/tools/lib/perf/threadmap.c
@@ -104,3 +104,15 @@ pid_t perf_thread_map__pid(struct perf_thread_map *map, int idx)
 
 	return map->map[idx].pid;
 }
+
+int perf_thread_map__idx(struct perf_thread_map *threads, pid_t pid)
+{
+	if (!threads)
+		return pid == -1 ? 0 : -1;
+
+	for (int i = 0; i < threads->nr; ++i) {
+		if (threads->map[i].pid == pid)
+			return i;
+	}
+	return -1;
+}
-- 
2.49.0.1101.gccaa498523-goog