tristate "Hung task detector test code"
depends on DETECT_HUNG_TASK && DEBUG_FS
help
- Build a module which provide a simple debugfs file. If user reads
- the file, it will sleep long time (256 seconds) with holding a
- mutex. Thus if there are 2 or more processes read this file, it
- will be detected by the hung_task watchdog.
+ Build a module that provides debugfs files (e.g., mutex, semaphore,
+ etc.) under <debugfs>/hung_task. If user reads one of these files,
+ it will sleep long time (256 seconds) with holding a lock. Thus,
+ if 2 or more processes read the same file concurrently, it will
+ be detected by the hung_task watchdog.
source "samples/rust/Kconfig"
+++ /dev/null
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * hung_task_mutex.c - Sample code which causes hung task by mutex
- *
- * Usage: load this module and read `<debugfs>/hung_task/mutex`
- * by 2 or more processes.
- *
- * This is for testing kernel hung_task error message.
- * Note that this will make your system freeze and maybe
- * cause panic. So do not use this except for the test.
- */
-
-#include <linux/debugfs.h>
-#include <linux/delay.h>
-#include <linux/fs.h>
-#include <linux/module.h>
-#include <linux/mutex.h>
-
-#define HUNG_TASK_DIR "hung_task"
-#define HUNG_TASK_FILE "mutex"
-#define SLEEP_SECOND 256
-
-static const char dummy_string[] = "This is a dummy string.";
-static DEFINE_MUTEX(dummy_mutex);
-static struct dentry *hung_task_dir;
-
-static ssize_t read_dummy(struct file *file, char __user *user_buf,
- size_t count, loff_t *ppos)
-{
- /* If the second task waits on the lock, it is uninterruptible sleep. */
- guard(mutex)(&dummy_mutex);
-
- /* When the first task sleep here, it is interruptible. */
- msleep_interruptible(SLEEP_SECOND * 1000);
-
- return simple_read_from_buffer(user_buf, count, ppos,
- dummy_string, sizeof(dummy_string));
-}
-
-static const struct file_operations hung_task_fops = {
- .read = read_dummy,
-};
-
-static int __init hung_task_sample_init(void)
-{
- hung_task_dir = debugfs_create_dir(HUNG_TASK_DIR, NULL);
- if (IS_ERR(hung_task_dir))
- return PTR_ERR(hung_task_dir);
-
- debugfs_create_file(HUNG_TASK_FILE, 0400, hung_task_dir,
- NULL, &hung_task_fops);
-
- return 0;
-}
-
-static void __exit hung_task_sample_exit(void)
-{
- debugfs_remove_recursive(hung_task_dir);
-}
-
-module_init(hung_task_sample_init);
-module_exit(hung_task_sample_exit);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Masami Hiramatsu");
-MODULE_DESCRIPTION("Simple sleep under mutex file for testing hung task");
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * hung_task_tests.c - Sample code for testing hung tasks with mutex,
+ * semaphore, etc.
+ *
+ * Usage: Load this module and read `<debugfs>/hung_task/mutex`,
+ * `<debugfs>/hung_task/semaphore`, etc., with 2 or more processes.
+ *
+ * This is for testing kernel hung_task error messages with various locking
+ * mechanisms (e.g., mutex, semaphore, etc.). Note that this may freeze
+ * your system or cause a panic. Use only for testing purposes.
+ */
+
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/semaphore.h>
+
+#define HUNG_TASK_DIR "hung_task"
+#define HUNG_TASK_MUTEX_FILE "mutex"
+#define HUNG_TASK_SEM_FILE "semaphore"
+#define SLEEP_SECOND 256
+
+static const char dummy_string[] = "This is a dummy string.";
+static DEFINE_MUTEX(dummy_mutex);
+static DEFINE_SEMAPHORE(dummy_sem, 1);
+static struct dentry *hung_task_dir;
+
+/* Mutex-based read function */
+static ssize_t read_dummy_mutex(struct file *file, char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ /* Second task waits on mutex, entering uninterruptible sleep */
+ guard(mutex)(&dummy_mutex);
+
+ /* First task sleeps here, interruptible */
+ msleep_interruptible(SLEEP_SECOND * 1000);
+
+ return simple_read_from_buffer(user_buf, count, ppos, dummy_string,
+ sizeof(dummy_string));
+}
+
+/* Semaphore-based read function */
+static ssize_t read_dummy_semaphore(struct file *file, char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ /* Second task waits on semaphore, entering uninterruptible sleep */
+ down(&dummy_sem);
+
+ /* First task sleeps here, interruptible */
+ msleep_interruptible(SLEEP_SECOND * 1000);
+
+ up(&dummy_sem);
+
+ return simple_read_from_buffer(user_buf, count, ppos, dummy_string,
+ sizeof(dummy_string));
+}
+
+/* File operations for mutex */
+static const struct file_operations hung_task_mutex_fops = {
+ .read = read_dummy_mutex,
+};
+
+/* File operations for semaphore */
+static const struct file_operations hung_task_sem_fops = {
+ .read = read_dummy_semaphore,
+};
+
+static int __init hung_task_tests_init(void)
+{
+ hung_task_dir = debugfs_create_dir(HUNG_TASK_DIR, NULL);
+ if (IS_ERR(hung_task_dir))
+ return PTR_ERR(hung_task_dir);
+
+ /* Create debugfs files for mutex and semaphore tests */
+ debugfs_create_file(HUNG_TASK_MUTEX_FILE, 0400, hung_task_dir, NULL,
+ &hung_task_mutex_fops);
+ debugfs_create_file(HUNG_TASK_SEM_FILE, 0400, hung_task_dir, NULL,
+ &hung_task_sem_fops);
+
+ return 0;
+}
+
+static void __exit hung_task_tests_exit(void)
+{
+ debugfs_remove_recursive(hung_task_dir);
+}
+
+module_init(hung_task_tests_init);
+module_exit(hung_task_tests_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Masami Hiramatsu <mhiramat@kernel.org>");
+MODULE_AUTHOR("Zi Li <amaindex@outlook.com>");
+MODULE_DESCRIPTION("Simple sleep under lock files for testing hung task");
projects / thirdparty / kernel / linux.git / commitdiff
