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perf thread_map: Skip exited threads when scanning /proc

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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>
Cc: James Clark <james.clark@arm.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Bill Wendling <morbo@google.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: llvm@lists.linux.dev
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240221034155.1500118-2-irogers@google.com
This commit is contained in:
Ian Rogers 2024-02-20 19:41:48 -08:00 committed by Namhyung Kim
parent b6968f9b50
commit 510e528786
1 changed files with 4 additions and 5 deletions
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9
tools/perf/util/thread_map.c
View file

@ -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;
}