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f96e8577 JFG |
1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* | |
3 | * Preempt / IRQ disable delay thread to test latency tracers | |
4 | * | |
5 | * Copyright (C) 2018 Joel Fernandes (Google) <joel@joelfernandes.org> | |
6 | */ | |
7 | ||
8 | #include <linux/delay.h> | |
9 | #include <linux/interrupt.h> | |
10 | #include <linux/irq.h> | |
11 | #include <linux/kernel.h> | |
12 | #include <linux/kthread.h> | |
13 | #include <linux/ktime.h> | |
14 | #include <linux/module.h> | |
15 | #include <linux/printk.h> | |
16 | #include <linux/string.h> | |
17 | ||
18 | static ulong delay = 100; | |
19 | static char test_mode[10] = "irq"; | |
20 | ||
21 | module_param_named(delay, delay, ulong, S_IRUGO); | |
22 | module_param_string(test_mode, test_mode, 10, S_IRUGO); | |
23 | MODULE_PARM_DESC(delay, "Period in microseconds (100 uS default)"); | |
24 | MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt or irq (default irq)"); | |
25 | ||
26 | static void busy_wait(ulong time) | |
27 | { | |
28 | ktime_t start, end; | |
29 | start = ktime_get(); | |
30 | do { | |
31 | end = ktime_get(); | |
32 | if (kthread_should_stop()) | |
33 | break; | |
34 | } while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000)); | |
35 | } | |
36 | ||
37 | int preemptirq_delay_run(void *data) | |
38 | { | |
39 | unsigned long flags; | |
40 | ||
41 | if (!strcmp(test_mode, "irq")) { | |
42 | local_irq_save(flags); | |
43 | busy_wait(delay); | |
44 | local_irq_restore(flags); | |
45 | } else if (!strcmp(test_mode, "preempt")) { | |
46 | preempt_disable(); | |
47 | busy_wait(delay); | |
48 | preempt_enable(); | |
49 | } | |
50 | ||
51 | return 0; | |
52 | } | |
53 | ||
54 | static int __init preemptirq_delay_init(void) | |
55 | { | |
56 | char task_name[50]; | |
57 | struct task_struct *test_task; | |
58 | ||
59 | snprintf(task_name, sizeof(task_name), "%s_test", test_mode); | |
60 | ||
61 | test_task = kthread_run(preemptirq_delay_run, NULL, task_name); | |
62 | return PTR_ERR_OR_ZERO(test_task); | |
63 | } | |
64 | ||
65 | static void __exit preemptirq_delay_exit(void) | |
66 | { | |
67 | return; | |
68 | } | |
69 | ||
70 | module_init(preemptirq_delay_init) | |
71 | module_exit(preemptirq_delay_exit) | |
72 | MODULE_LICENSE("GPL v2"); |