[PATCH v5 1/8] perf thread_map: Skip exited threads when scanning /proc

Ian Rogers
2024-02-16T23:55:15Z

Scanning /proc is inherently racy. Scanning /proc/pid/task within that
is also racy as the pid can terminate. Rather than failing in
__thread_map__new_all_cpus, skip pids for such failures.

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/thread_map.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/thread_map.c b/tools/perf/util/thread_map.c
index ea3b431b9783..b5f12390c355 100644
--- a/tools/perf/util/thread_map.c
+++ b/tools/perf/util/thread_map.c
@@ -109,9 +109,10 @@ static struct perf_thread_map *__thread_map__new_all_cpus(uid_t uid)

snprintf(path, sizeof(path), "/proc/%d/task", pid);
items = scandir(path, &namelist, filter, NULL);
- if (items <= 0)
- goto out_free_closedir;
-
+ if (items <= 0) {
+ pr_debug("scandir for %d returned empty, skipping\n", pid);
+ continue;
+ }
while (threads->nr + items >= max_threads) {
max_threads *= 2;
grow = true;
@@ -152,8 +153,6 @@ static struct perf_thread_map *__thread_map__new_all_cpus(uid_t uid)
for (i = 0; i < items; i++)
zfree(&namelist[i]);
free(namelist);
-
-out_free_closedir:
zfree(&threads);
goto out_closedir;
}
--
2.44.0.rc0.258.g7320e95886-goog