perf tools: Add read_all_cgroups() and __cgroup_find()

The read_all_cgroups() is to build a tree of cgroups in the system and
users can look up a cgroup using __cgroup_find().

Committer notes:

Had to do this to cover that #else block:

  -static inline u64 __read_cgroup_id(const char *path) { return -1ULL; }
  +static inline u64 __read_cgroup_id(const char *path __maybe_unused) { return -1ULL; }

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230906174903.346486-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/tools/perf/util/cgroup.h b/tools/perf/util/cgroup.h
index 12256b78608c..beb6fe1012ed 100644
--- a/tools/perf/util/cgroup.h
+++ b/tools/perf/util/cgroup.h
@@ -37,6 +37,7 @@ int parse_cgroups(const struct option *opt, const char *str, int unset);
 struct cgroup *cgroup__findnew(struct perf_env *env, uint64_t id,
 			       const char *path);
 struct cgroup *cgroup__find(struct perf_env *env, uint64_t id);
+struct cgroup *__cgroup__find(struct rb_root *root, uint64_t id);
 
 void perf_env__purge_cgroups(struct perf_env *env);
 
@@ -49,6 +50,9 @@ static inline int read_cgroup_id(struct cgroup *cgrp __maybe_unused)
 }
 #endif  /* HAVE_FILE_HANDLE */
 
+/* read all cgroups in the system and save them in the rbtree */
+void read_all_cgroups(struct rb_root *root);
+
 int cgroup_is_v2(const char *subsys);
 
 #endif /* __CGROUP_H__ */