[PATCH 3.16 356/366] perf tools: Use readdir() instead of deprecated readdir_r()

Ben Hutchings
2018-11-11T20:30:47Z

From: Arnaldo Carvalho de Melo <acme@redhat.com>

commit 7093b4c963cc4e344e490c774924a180602a7092 upstream.

The readdir() function is thread safe as long as just one thread uses a
DIR, which is the case when synthesizing events for pre-existing threads
by traversing /proc, 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 /tmp/build/perf/util/event.o
util/event.c: In function '__event__synthesize_thread':
util/event.c:466:2: error: 'readdir_r' is deprecated [-Werror=deprecated-declarations]
while (!readdir_r(tasks, &dirent, &next) && next) {
^~~~~
In file included from /usr/include/features.h:368:0,
from /usr/include/stdint.h:25,
from /usr/lib/gcc/x86_64-redhat-linux/6.0.0/include/stdint.h:9,
from /git/linux/tools/include/linux/types.h:6,
from util/event.c:1:
/usr/include/dirent.h:189:12: note: declared here

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-i1vj7nyjp2p750rirxgrfd3c@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
tools/perf/util/event.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -331,7 +331,7 @@ static int __event__synthesize_thread(un
{
char filename[PATH_MAX];
DIR *tasks;
- struct dirent dirent, *next;
+ struct dirent *dirent;
pid_t tgid;

/* special case: only send one comm event using passed in pid */
@@ -358,12 +358,12 @@ static int __event__synthesize_thread(un
return 0;
}

- while (!readdir_r(tasks, &dirent, &next) && next) {
+ while ((dirent = readdir(tasks)) != NULL) {
char *end;
int rc = 0;
pid_t _pid;

- _pid = strtol(dirent.d_name, &end, 10);
+ _pid = strtol(dirent->d_name, &end, 10);
if (*end)
continue;

@@ -464,7 +464,7 @@ int perf_event__synthesize_threads(struc
{
DIR *proc;
char proc_path[PATH_MAX];
- struct dirent dirent, *next;
+ struct dirent *dirent;
union perf_event *comm_event, *mmap_event, *fork_event;
int err = -1;

@@ -489,9 +489,9 @@ int perf_event__synthesize_threads(struc
if (proc == NULL)
goto out_free_fork;

- while (!readdir_r(proc, &dirent, &next) && next) {
+ while ((dirent = readdir(proc)) != NULL) {
char *end;
- 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 */
continue;