[tip:perf/core] perf hists: Do not link a pair if already linked

[tip-bot for Arnaldo Carvalho de Melo]

Commit-ID:  7d1a5efa20dbfea97cb93b99c67ce5cd5c4a4dbc
Gitweb:     https://git.kernel.org/tip/7d1a5efa20dbfea97cb93b99c67ce5cd5c4a4dbc
Author:     Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Wed, 7 Aug 2019 10:45:30 -0300
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Mon, 12 Aug 2019 16:26:02 -0300

perf hists: Do not link a pair if already linked

When we have multiple events in a group we link hist_entries in the
non-leader evsel hists to the one in the leader that points to the same
sorting criteria, in hists__match().

For 'perf report' we do this just once and then print the results, but
for 'perf top' we need to look if this was already done in the previous
refresh of the screen, so check for that and don't try to link again.

This is part of having 'perf top' using the hists browser for showing
multiple events in multiple columns.

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Link: https://lkml.kernel.org/n/tip-iwvb37rgb7upswhruwpcdnhw@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/hist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 4297f56b1e05..d923a5bb7b48 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -2453,7 +2453,7 @@ void hists__match(struct hists *leader, struct hists *other)
 		pos  = rb_entry(nd, struct hist_entry, rb_node_in);
 		pair = hists__find_entry(other, pos);
 
-		if (pair)
+		if (pair && list_empty(&pair->pairs.node))
 			hist_entry__add_pair(pair, pos);
 	}
 }