perf: allow command to attach local data to thread/evsel structs

[David Ahern <dsahern@gmail.com>]

This is an API I have been using for some 'local' commands that process
perf events. It allows the commands to attach data to events and threads
and avoid local caching and lookups.


diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 326b8e4..866de40 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -66,6 +66,12 @@ struct perf_evsel {
        void        *data;
    } handler;
    bool            supported;
+
+   /*
+    * can be used by commands that process samples
+    * for storing local, event-based data
+    */
+   void *private;
 };

 struct cpu_map;
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 70c2c13..9f62859 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -16,6 +16,12 @@ struct thread {
    bool            comm_set;
    char            *comm;
    int         comm_len;
+
+    /*
+    * can be used by commands that process samples
+    * for storing local, thread-based data
+    */
+   void *private;
 };

 struct machine;

One wrinkle is that for the thread-based one the thread__delete(),
thread__fork() and thread__set_comm() functions would free the
allocations if set -- or a handler is needed to free private structs to
handle layered mallocs.

Any objections to pushing this kind of open-ended API into perf?

David