mirror of https://github.com/torvalds/linux.git
67 lines
1.8 KiB
C
67 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* hung_task_mutex.c - Sample code which causes hung task by mutex
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*
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* Usage: load this module and read `<debugfs>/hung_task/mutex`
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* by 2 or more processes.
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*
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* This is for testing kernel hung_task error message.
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* Note that this will make your system freeze and maybe
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* cause panic. So do not use this except for the test.
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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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#define HUNG_TASK_DIR "hung_task"
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#define HUNG_TASK_FILE "mutex"
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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 struct dentry *hung_task_dir;
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static ssize_t read_dummy(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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/* If the second task waits on the lock, it is uninterruptible sleep. */
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guard(mutex)(&dummy_mutex);
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/* When the first task sleep here, it is interruptible. */
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msleep_interruptible(SLEEP_SECOND * 1000);
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return simple_read_from_buffer(user_buf, count, ppos,
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dummy_string, sizeof(dummy_string));
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}
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static const struct file_operations hung_task_fops = {
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.read = read_dummy,
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};
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static int __init hung_task_sample_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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debugfs_create_file(HUNG_TASK_FILE, 0400, hung_task_dir,
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NULL, &hung_task_fops);
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return 0;
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}
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static void __exit hung_task_sample_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_sample_init);
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module_exit(hung_task_sample_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Masami Hiramatsu");
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MODULE_DESCRIPTION("Simple sleep under mutex file for testing hung task");
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