selftests/damon: add a test for a race between target_ids_read() and dbgfs_before_ter...

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@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/damon/.gitignore b/tools/testing/selftests/damon/.gitignore
index c6c2965a660754e9d0acc8aeb676272a374bc4d0..7d6c6e062be7f74cd998d9f99104a0f51a8a8d94 100644 (file)
--- 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 b545fedafb3b9fc184b7526465fe5d04f67e3725..8a3a8df003dbb85cb88cea65ac31ed4e7ed9fb87 100644 (file)
--- 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 (file)
index 0000000..b06f52a
--- /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@kernel.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 100644 (file)
index 0000000..fc793c4
--- /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