linux-kernel - [PATCH v1 5/5] perf test: In forked mode add check that fds aren't leaked

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Message-ID: <20250624190326.2038704-6-irogers@google.com>
Date: Tue, 24 Jun 2025 12:03:25 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@...aro.org>, 
	Howard Chu <howardchu95@...il.com>, Charlie Jenkins <charlie@...osinc.com>, 
	Thomas Richter <tmricht@...ux.ibm.com>, Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, 
	Stephen Brennan <stephen.s.brennan@...cle.com>, 
	Jean-Philippe Romain <jean-philippe.romain@...s.st.com>, Junhao He <hejunhao3@...wei.com>, 
	"Dr. David Alan Gilbert" <linux@...blig.org>, Dmitry Vyukov <dvyukov@...gle.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v1 5/5] perf test: In forked mode add check that fds aren't leaked

When a test is forked no file descriptors should be open, however,
parent ones may have been inherited - in particular those of the pipes
of other forked child test processes. Add a loop to clean-up/close
those file descriptors prior to running the test. At the end of the
test assert that no additional file descriptors are present as this
would indicate a file descriptor leak.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/tests/builtin-test.c | 69 +++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index 45d3d8b3317a..4061d5d969aa 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -4,6 +4,7 @@
  *
  * Builtin regression testing command: ever growing number of sanity tests
  */
+#include <ctype.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <poll.h>
@@ -155,6 +156,71 @@ static struct test_workload *workloads[] = {
 #define test_suite__for_each_test_case(suite, idx)			\
 	for (idx = 0; (suite)->test_cases && (suite)->test_cases[idx].name != NULL; idx++)
 
+static void close_parent_fds(void)
+{
+	DIR *dir = opendir("/proc/self/fd");
+	struct dirent *ent;
+
+	while ((ent = readdir(dir))) {
+		char *end;
+		long fd;
+
+		if (ent->d_type != DT_LNK)
+			continue;
+
+		if (!isdigit(ent->d_name[0]))
+			continue;
+
+		fd = strtol(ent->d_name, &end, 10);
+		if (*end)
+			continue;
+
+		if (fd <= 3 || fd == dirfd(dir))
+			continue;
+
+		close(fd);
+	}
+	closedir(dir);
+}
+
+static void check_leaks(void)
+{
+	DIR *dir = opendir("/proc/self/fd");
+	struct dirent *ent;
+	int leaks = 0;
+
+	while ((ent = readdir(dir))) {
+		char path[PATH_MAX];
+		char *end;
+		long fd;
+		ssize_t len;
+
+		if (ent->d_type != DT_LNK)
+			continue;
+
+		if (!isdigit(ent->d_name[0]))
+			continue;
+
+		fd = strtol(ent->d_name, &end, 10);
+		if (*end)
+			continue;
+
+		if (fd <= 3 || fd == dirfd(dir))
+			continue;
+
+		leaks++;
+		len = readlinkat(dirfd(dir), ent->d_name, path, sizeof(path));
+		if (len > 0 && (size_t)len < sizeof(path))
+			path[len] = '\0';
+		else
+			strncpy(path, ent->d_name, sizeof(path));
+		pr_err("Leak of file descriptor %s that opened: '%s'\n", ent->d_name, path);
+	}
+	closedir(dir);
+	if (leaks)
+		abort();
+}
+
 static int test_suite__num_test_cases(const struct test_suite *t)
 {
 	int num;
@@ -242,6 +308,8 @@ static int run_test_child(struct child_process *process)
 	struct child_test *child = container_of(process, struct child_test, process);
 	int err;
 
+	close_parent_fds();
+
 	err = sigsetjmp(run_test_jmp_buf, 1);
 	if (err) {
 		fprintf(stderr, "\n---- unexpected signal (%d) ----\n", err);
@@ -257,6 +325,7 @@ static int run_test_child(struct child_process *process)
 	err = test_function(child->test, child->test_case_num)(child->test, child->test_case_num);
 	pr_debug("---- end(%d) ----\n", err);
 
+	check_leaks();
 err_out:
 	fflush(NULL);
 	for (size_t i = 0; i < ARRAY_SIZE(signals); i++)
-- 
2.50.0.714.g196bf9f422-goog