The patch titled
Subject: selftests/damon: add a test for a race between target_ids_read() and dbgfs_before_terminate()
has been added to the -mm mm-unstable branch. Its filename is
selftests-damon-add-a-test-for-a-race-between-target_ids_read-and-dbgfs_before_terminate.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-damon-add-a-test-for-a-race-between-target_ids_read-and-dbgfs_before_terminate.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: SeongJae Park <sj@xxxxxxxxxx>
Subject: selftests/damon: add a test for a race between target_ids_read() and dbgfs_before_terminate()
Date: Wed, 7 Feb 2024 12:31:32 -0800
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.
Link: https://lkml.kernel.org/r/20240207203134.69976-7-sj@xxxxxxxxxx
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/damon/.gitignore | 1
tools/testing/selftests/damon/Makefile | 2
tools/testing/selftests/damon/debugfs_target_ids_read_before_terminate_race.c | 80 ++++++++++
tools/testing/selftests/damon/debugfs_target_ids_read_before_terminate_race.sh | 14 +
4 files changed, 97 insertions(+)
--- /dev/null
+++ a/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@xxxxxxxxxx>
+ */
+#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;
+}
--- /dev/null
+++ a/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
--- a/tools/testing/selftests/damon/.gitignore~selftests-damon-add-a-test-for-a-race-between-target_ids_read-and-dbgfs_before_terminate
+++ a/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
--- a/tools/testing/selftests/damon/Makefile~selftests-damon-add-a-test-for-a-race-between-target_ids_read-and-dbgfs_before_terminate
+++ a/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_sc
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
_
Patches currently in -mm which might be from sj@xxxxxxxxxx are
mm-damon-sysfs-schemes-fix-wrong-damos-tried-regions-update-timeout-setup.patch
mm-damon-core-check-apply-interval-in-damon_do_apply_schemes.patch
docs-admin-guide-mm-damon-usage-use-sysfs-interface-for-tracepoints-example.patch
mm-damon-rename-config_damon_dbgfs-to-damon_dbgfs_deprecated.patch
mm-damon-dbgfs-implement-deprecation-notice-file.patch
mm-damon-dbgfs-make-debugfs-interface-deprecation-message-a-macro.patch
docs-admin-guide-mm-damon-usage-document-deprecated-file-of-damon-debugfs-interface.patch
selftets-damon-prepare-for-monitor_on-file-renaming.patch
mm-damon-dbgfs-rename-monitor_on-file-to-monitor_on_deprecated.patch
docs-admin-guide-mm-damon-usage-update-for-monitor_on-renaming.patch
docs-translations-damon-usage-update-for-monitor_on-renaming.patch
mm-damon-sysfs-handle-state-file-inputs-for-every-sampling-interval-if-possible.patch
selftests-damon-_damon_sysfs-support-damos-quota.patch
selftests-damon-_damon_sysfs-support-damos-stats.patch
selftests-damon-_damon_sysfs-support-damos-apply-interval.patch
selftests-damon-add-a-test-for-damos-quota.patch
selftests-damon-add-a-test-for-damos-apply-intervals.patch
selftests-damon-add-a-test-for-a-race-between-target_ids_read-and-dbgfs_before_terminate.patch
selftests-damon-add-a-test-for-the-pid-leak-of-dbgfs_target_ids_write.patch
selftests-damon-_chk_dependency-get-debugfs-mount-point-from-proc-mounts.patch
