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Message-Id: <20240207203134.69976-7-sj@kernel.org>
Date: Wed, 7 Feb 2024 12:31:32 -0800
From: SeongJae Park <sj@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: SeongJae Park <sj@...nel.org>,
Shuah Khan <shuah@...nel.org>,
damon@...ts.linux.dev,
linux-mm@...ck.org,
linux-kselftest@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 6/8] selftests/damon: add a test for a race between target_ids_read() and dbgfs_before_terminate()
commit 34796417964b ("mm/damon/dbgfs: protect targets destructions with
kdamond_lock") fixed a race of DAMON debugfs interface. Specifically,
the race was happening between target_ids_read() and
dbgfs_before_terminate(). Add a test for the issue to prevent the
problem from accidentally recurring.
Signed-off-by: SeongJae Park <sj@...nel.org>
---
tools/testing/selftests/damon/.gitignore | 1 +
tools/testing/selftests/damon/Makefile | 2 +
...fs_target_ids_read_before_terminate_race.c | 80 +++++++++++++++++++
...s_target_ids_read_before_terminate_race.sh | 14 ++++
4 files changed, 97 insertions(+)
create mode 100644 tools/testing/selftests/damon/debugfs_target_ids_read_before_terminate_race.c
create mode 100755 tools/testing/selftests/damon/debugfs_target_ids_read_before_terminate_race.sh
diff --git a/tools/testing/selftests/damon/.gitignore b/tools/testing/selftests/damon/.gitignore
index c6c2965a6607..7d6c6e062be7 100644
--- a/tools/testing/selftests/damon/.gitignore
+++ b/tools/testing/selftests/damon/.gitignore
@@ -1,2 +1,3 @@
# SPDX-License-Identifier: GPL-2.0-only
huge_count_read_write
+debugfs_target_ids_read_before_terminate_race
diff --git a/tools/testing/selftests/damon/Makefile b/tools/testing/selftests/damon/Makefile
index b545fedafb3b..8a3a8df003db 100644
--- a/tools/testing/selftests/damon/Makefile
+++ b/tools/testing/selftests/damon/Makefile
@@ -2,6 +2,7 @@
# Makefile for damon selftests
TEST_GEN_FILES += huge_count_read_write
+TEST_GEN_FILES += debugfs_target_ids_read_before_terminate_race
TEST_GEN_FILES += access_memory
TEST_FILES = _chk_dependency.sh _debugfs_common.sh
@@ -9,6 +10,7 @@ TEST_PROGS = debugfs_attrs.sh debugfs_schemes.sh debugfs_target_ids.sh
TEST_PROGS += debugfs_empty_targets.sh debugfs_huge_count_read_write.sh
TEST_PROGS += debugfs_duplicate_context_creation.sh
TEST_PROGS += debugfs_rm_non_contexts.sh
+TEST_PROGS += debugfs_target_ids_read_before_terminate_race.sh
TEST_PROGS += sysfs.sh sysfs_update_removed_scheme_dir.sh
TEST_PROGS += sysfs_update_schemes_tried_regions_hang.py
TEST_PROGS += sysfs_update_schemes_tried_regions_wss_estimation.py
diff --git a/tools/testing/selftests/damon/debugfs_target_ids_read_before_terminate_race.c b/tools/testing/selftests/damon/debugfs_target_ids_read_before_terminate_race.c
new file mode 100644
index 000000000000..b06f52a8ce2d
--- /dev/null
+++ b/tools/testing/selftests/damon/debugfs_target_ids_read_before_terminate_race.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Author: SeongJae Park <sj@...nel.org>
+ */
+#define _GNU_SOURCE
+
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <time.h>
+#include <unistd.h>
+
+#define DBGFS_MONITOR_ON "/sys/kernel/debug/damon/monitor_on_DEPRECATED"
+#define DBGFS_TARGET_IDS "/sys/kernel/debug/damon/target_ids"
+
+static void turn_damon_on_exit(void)
+{
+ int target_ids_fd = open(DBGFS_TARGET_IDS, O_RDWR);
+ int monitor_on_fd = open(DBGFS_MONITOR_ON, O_RDWR);
+ char pid_str[128];
+
+ snprintf(pid_str, sizeof(pid_str), "%d", getpid());
+ write(target_ids_fd, pid_str, sizeof(pid_str));
+ write(monitor_on_fd, "on\n", 3);
+ close(target_ids_fd);
+ close(monitor_on_fd);
+ usleep(1000);
+ exit(0);
+}
+
+static void try_race(void)
+{
+ int target_ids_fd = open(DBGFS_TARGET_IDS, O_RDWR);
+ int pid = fork();
+ int buf[256];
+
+ if (pid < 0) {
+ fprintf(stderr, "fork() failed\n");
+ exit(1);
+ }
+ if (pid == 0)
+ turn_damon_on_exit();
+ while (true) {
+ int status;
+
+ read(target_ids_fd, buf, sizeof(buf));
+ if (waitpid(-1, &status, WNOHANG) == pid)
+ break;
+ }
+ close(target_ids_fd);
+}
+
+static inline uint64_t ts_to_ms(struct timespec *ts)
+{
+ return (uint64_t)ts->tv_sec * 1000 + (uint64_t)ts->tv_nsec / 1000000;
+}
+
+int main(int argc, char *argv[])
+{
+ struct timespec start_time, now;
+ int runtime_ms;
+
+ if (argc != 2) {
+ fprintf(stderr, "Usage: %s <runtime in ms>\n", argv[0]);
+ exit(1);
+ }
+ runtime_ms = atoi(argv[1]);
+ clock_gettime(CLOCK_MONOTONIC, &start_time);
+ while (true) {
+ try_race();
+ clock_gettime(CLOCK_MONOTONIC, &now);
+ if (ts_to_ms(&now) - ts_to_ms(&start_time) > runtime_ms)
+ break;
+ }
+ return 0;
+}
diff --git a/tools/testing/selftests/damon/debugfs_target_ids_read_before_terminate_race.sh b/tools/testing/selftests/damon/debugfs_target_ids_read_before_terminate_race.sh
new file mode 100755
index 000000000000..fc793c4c9aea
--- /dev/null
+++ b/tools/testing/selftests/damon/debugfs_target_ids_read_before_terminate_race.sh
@@ -0,0 +1,14 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+dmesg -C
+
+./debugfs_target_ids_read_before_terminate_race 5000
+
+if dmesg | grep -q dbgfs_target_ids_read
+then
+ dmesg
+ exit 1
+else
+ exit 0
+fi
--
2.39.2
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