From 5141d7350d3d8a12f1f76b1015b937f14d2b97e2 Mon Sep 17 00:00:00 2001 From: Wang Nan Date: Fri, 5 Feb 2016 14:01:30 +0000 Subject: [PATCH] perf data: Fix releasing event_class A new patch in libbabeltrace [1] reveals a object leak problem in 'perf data' CTF support: perf code never releases the event_class which is allocated in add_event() and stored in evsel's private field. If libbabeltrace has the above patch applied, leaking event_class prevents the writer from being destroyed and flushing metadata. For example: $ perf record ls perf.data [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.012 MB perf.data (12 samples) ] $ perf data convert --to-ctf ./out.ctf [ perf data convert: Converted 'perf.data' into CTF data './out.ctf' ] [ perf data convert: Converted and wrote 0.000 MB (12 samples) ] $ cat ./out.ctf/metadata $ ls -l ./out.ctf/metadata -rw-r----- 1 w00229757 mm 0 Jan 27 10:49 ./out.ctf/metadata The correct result should be: ... $ cat ./out.ctf/metadata /* CTF 1.8 */ trace { [SNIP] $ ls -l ./out.ctf/metadata -rw-r----- 1 w00229757 mm 2446 Jan 27 10:52 ./out.ctf/metadata The full story is: Patch [1] of babeltrace redesigns its reference counting scheme. In that patch: * writer <- trace (bt_ctf_writer_create) * trace <- stream_class (bt_ctf_trace_add_stream_class) * stream_class <- event_class (bt_ctf_stream_class_add_event_class) ('<-' means 'is a parent of') Holding of event_class causes reference count of corresponding 'writer' to increase through parent chain. Perf expects that 'writer' is released (so metadata is flushed) through bt_ctf_writer_put() in ctf_writer__cleanup(). However, since it never releases event_class, the reference of 'writer' won't be dropped, so bt_ctf_writer_put() won't lead to the release of writer. Before this CTF patch, !(writer <- trace). Even with event_class leaking, the writer ends up being released. [1] https://github.com/efficios/babeltrace/commit/e6a8e8e4744633807083a077ff9f101eb97d9801 Signed-off-by: Wang Nan Acked-by: Jiri Olsa Cc: Adrian Hunter Cc: Alexei Starovoitov Cc: Brendan Gregg Cc: Cody P Schafer Cc: He Kuang Cc: Jeremie Galarneau Cc: Kirill Smelkov Cc: Li Zefan Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Zefan Li Cc: pi3orama@163.com Link: http://lkml.kernel.org/r/1454680939-24963-6-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/data-convert-bt.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c index 34cd1e4039d3..b722e57d5a87 100644 --- a/tools/perf/util/data-convert-bt.c +++ b/tools/perf/util/data-convert-bt.c @@ -858,6 +858,23 @@ static int setup_events(struct ctf_writer *cw, struct perf_session *session) return 0; } +static void cleanup_events(struct perf_session *session) +{ + struct perf_evlist *evlist = session->evlist; + struct perf_evsel *evsel; + + evlist__for_each(evlist, evsel) { + struct evsel_priv *priv; + + priv = evsel->priv; + bt_ctf_event_class_put(priv->event_class); + zfree(&evsel->priv); + } + + perf_evlist__delete(evlist); + session->evlist = NULL; +} + static int setup_streams(struct ctf_writer *cw, struct perf_session *session) { struct ctf_stream **stream; @@ -1171,6 +1188,7 @@ int bt_convert__perf2ctf(const char *input, const char *path, bool force) (double) c.events_size / 1024.0 / 1024.0, c.events_count); + cleanup_events(session); perf_session__delete(session); ctf_writer__cleanup(cw); -- GitLab