mirror of https://github.com/torvalds/linux.git
98 lines
2.8 KiB
C
98 lines
2.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* hung_task_tests.c - Sample code for testing hung tasks with mutex,
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* semaphore, etc.
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*
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* Usage: Load this module and read `<debugfs>/hung_task/mutex`,
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* `<debugfs>/hung_task/semaphore`, etc., with 2 or more processes.
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*
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* This is for testing kernel hung_task error messages with various locking
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* mechanisms (e.g., mutex, semaphore, etc.). Note that this may freeze
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* your system or cause a panic. Use only for testing purposes.
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*/
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#include <linux/debugfs.h>
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#include <linux/delay.h>
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#include <linux/fs.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/semaphore.h>
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#define HUNG_TASK_DIR "hung_task"
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#define HUNG_TASK_MUTEX_FILE "mutex"
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#define HUNG_TASK_SEM_FILE "semaphore"
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#define SLEEP_SECOND 256
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static const char dummy_string[] = "This is a dummy string.";
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static DEFINE_MUTEX(dummy_mutex);
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static DEFINE_SEMAPHORE(dummy_sem, 1);
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static struct dentry *hung_task_dir;
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/* Mutex-based read function */
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static ssize_t read_dummy_mutex(struct file *file, char __user *user_buf,
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size_t count, loff_t *ppos)
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{
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/* Second task waits on mutex, entering uninterruptible sleep */
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guard(mutex)(&dummy_mutex);
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/* First task sleeps here, interruptible */
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msleep_interruptible(SLEEP_SECOND * 1000);
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return simple_read_from_buffer(user_buf, count, ppos, dummy_string,
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sizeof(dummy_string));
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}
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/* Semaphore-based read function */
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static ssize_t read_dummy_semaphore(struct file *file, char __user *user_buf,
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size_t count, loff_t *ppos)
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{
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/* Second task waits on semaphore, entering uninterruptible sleep */
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down(&dummy_sem);
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/* First task sleeps here, interruptible */
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msleep_interruptible(SLEEP_SECOND * 1000);
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up(&dummy_sem);
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return simple_read_from_buffer(user_buf, count, ppos, dummy_string,
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sizeof(dummy_string));
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}
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/* File operations for mutex */
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static const struct file_operations hung_task_mutex_fops = {
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.read = read_dummy_mutex,
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};
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/* File operations for semaphore */
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static const struct file_operations hung_task_sem_fops = {
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.read = read_dummy_semaphore,
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};
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static int __init hung_task_tests_init(void)
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{
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hung_task_dir = debugfs_create_dir(HUNG_TASK_DIR, NULL);
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if (IS_ERR(hung_task_dir))
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return PTR_ERR(hung_task_dir);
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/* Create debugfs files for mutex and semaphore tests */
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debugfs_create_file(HUNG_TASK_MUTEX_FILE, 0400, hung_task_dir, NULL,
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&hung_task_mutex_fops);
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debugfs_create_file(HUNG_TASK_SEM_FILE, 0400, hung_task_dir, NULL,
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&hung_task_sem_fops);
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return 0;
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}
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static void __exit hung_task_tests_exit(void)
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{
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debugfs_remove_recursive(hung_task_dir);
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}
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module_init(hung_task_tests_init);
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module_exit(hung_task_tests_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Masami Hiramatsu <mhiramat@kernel.org>");
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MODULE_AUTHOR("Zi Li <amaindex@outlook.com>");
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MODULE_DESCRIPTION("Simple sleep under lock files for testing hung task");
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