linux-kernel - [PATCH] perf python: Do not force closing original perf descriptor in evlist.get

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Date:   Wed, 26 Dec 2018 12:21:21 +0100
From:   Jiri Olsa <jolsa@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ondřej Lysoněk <olysonek@...hat.com>
Subject: [PATCH] perf python: Do not force closing original perf descriptor in evlist.get_pollfd

Ondřej reported that when compiled with python3, the python
extension regress in evlist.get_pollfd function behaviour.

The evlist.get_pollfd creates file objects from evlist's fds
and returns them in the list. The python3 version also sets
them to 'close the original descriptor' when the object die
(is closed), by passing True via 'closefd' arg in PyFile_FromFd
call.

The python's closefd doc says:
  If closefd is False, the underlying file descriptor will be kept open
  when the file is closed.

That's why following line in python3 closes all evlist fds:
  evlist.get_pollfd()

the returned list is immediately destroyed and that takes
down the original events fds.

Passing closefd as False to PyFile_FromFd to fix this.

Reported-by: Ondřej Lysoněk <olysonek@...hat.com>
Link: http://lkml.kernel.org/n/tip-ru9hmsaliew8p01kr0050mvg@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/perf/util/python.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
index 47628e85c5eb..dda0ac978b1e 100644
--- a/tools/perf/util/python.c
+++ b/tools/perf/util/python.c
@@ -939,7 +939,8 @@ static PyObject *pyrf_evlist__get_pollfd(struct pyrf_evlist *pevlist,

 		file = PyFile_FromFile(fp, "perf", "r", NULL);
 #else
-		file = PyFile_FromFd(evlist->pollfd.entries[i].fd, "perf", "r", -1, NULL, NULL, NULL, 1);
+		file = PyFile_FromFd(evlist->pollfd.entries[i].fd, "perf", "r", -1,
+				     NULL, NULL, NULL, 0);
 #endif
 		if (file == NULL)
 			goto free_list;
-- 
2.17.2