[PATCH 4.4 41/57] perf thread_map: Use readdir() instead of deprecated readdir_r()

From: Greg Kroah-Hartman
Date: Thu Jul 13 2017 - 11:50:35 EST

4.4-stable review patch. If anyone has any objections, please let me know.


From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

commit 3354cf71104de49326d19d2f9bdb1f66eea52ef4 upstream.

The readdir() function is thread safe as long as just one thread uses a
DIR, which is the case in thread_map, so, to avoid breaking the build
with glibc-2.23.90 (upcoming 2.24), use it instead of readdir_r().

See: http://man7.org/linux/man-pages/man3/readdir.3.html

"However, in modern implementations (including the glibc implementation),
concurrent calls to readdir() that specify different directory streams
are thread-safe. In cases where multiple threads must read from the
same directory stream, using readdir() with external synchronization is
still preferable to the use of the deprecated readdir_r(3) function."

Noticed while building on a Fedora Rawhide docker container.

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-del8h2a0f40z75j4r42l96l0@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

tools/perf/util/thread_map.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/tools/perf/util/thread_map.c
+++ b/tools/perf/util/thread_map.c
@@ -93,7 +93,7 @@ struct thread_map *thread_map__new_by_ui
DIR *proc;
int max_threads = 32, items, i;
char path[NAME_MAX + 1 + 6];
- struct dirent dirent, *next, **namelist = NULL;
+ struct dirent *dirent, **namelist = NULL;
struct thread_map *threads = thread_map__alloc(max_threads);

if (threads == NULL)
@@ -106,16 +106,16 @@ struct thread_map *thread_map__new_by_ui
threads->nr = 0;
atomic_set(&threads->refcnt, 1);

- while (!readdir_r(proc, &dirent, &next) && next) {
+ while ((dirent = readdir(proc)) != NULL) {
char *end;
bool grow = false;
struct stat st;
- pid_t pid = strtol(dirent.d_name, &end, 10);
+ pid_t pid = strtol(dirent->d_name, &end, 10);

if (*end) /* only interested in proper numerical dirents */

- snprintf(path, sizeof(path), "/proc/%s", dirent.d_name);
+ snprintf(path, sizeof(path), "/proc/%s", dirent->d_name);

if (stat(path, &st) != 0)