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/trace_clock.h>
9#include <linux/delay.h>
10#include <linux/interrupt.h>
11#include <linux/irq.h>
12#include <linux/kernel.h>
13#include <linux/kobject.h>
14#include <linux/kthread.h>
15#include <linux/module.h>
16#include <linux/printk.h>
17#include <linux/string.h>
18#include <linux/sysfs.h>
19#include <linux/completion.h>
20
21static ulong delay = 100;
22static char test_mode[12] = "irq";
23static uint burst_size = 1;
24static int  cpu_affinity = -1;
25
26module_param_named(delay, delay, ulong, 0444);
27module_param_string(test_mode, test_mode, 12, 0444);
28module_param_named(burst_size, burst_size, uint, 0444);
29module_param_named(cpu_affinity, cpu_affinity, int, 0444);
30MODULE_PARM_DESC(delay, "Period in microseconds (100 us default)");
31MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt, irq, or alternate (default irq)");
32MODULE_PARM_DESC(burst_size, "The size of a burst (default 1)");
33MODULE_PARM_DESC(cpu_affinity, "Cpu num test is running on");
34
35static struct completion done;
36
37#define MIN(x, y) ((x) < (y) ? (x) : (y))
38
39static void busy_wait(ulong time)
40{
41	u64 start, end;
42
43	start = trace_clock_local();
44
45	do {
46		end = trace_clock_local();
47		if (kthread_should_stop())
48			break;
49	} while ((end - start) < (time * 1000));
50}
51
52static __always_inline void irqoff_test(void)
53{
54	unsigned long flags;
55
56	local_irq_save(flags);
57	busy_wait(delay);
58	local_irq_restore(flags);
59}
60
61static __always_inline void preemptoff_test(void)
62{
63	preempt_disable();
64	busy_wait(delay);
65	preempt_enable();
66}
67
68static void execute_preemptirqtest(int idx)
69{
70	if (!strcmp(test_mode, "irq"))
71		irqoff_test();
72	else if (!strcmp(test_mode, "preempt"))
73		preemptoff_test();
74	else if (!strcmp(test_mode, "alternate")) {
75		if (idx % 2 == 0)
76			irqoff_test();
77		else
78			preemptoff_test();
79	}
80}
81
82#define DECLARE_TESTFN(POSTFIX)				\
83	static void preemptirqtest_##POSTFIX(int idx)	\
84	{						\
85		execute_preemptirqtest(idx);		\
86	}						\
87
88/*
89 * We create 10 different functions, so that we can get 10 different
90 * backtraces.
91 */
92DECLARE_TESTFN(0)
93DECLARE_TESTFN(1)
94DECLARE_TESTFN(2)
95DECLARE_TESTFN(3)
96DECLARE_TESTFN(4)
97DECLARE_TESTFN(5)
98DECLARE_TESTFN(6)
99DECLARE_TESTFN(7)
100DECLARE_TESTFN(8)
101DECLARE_TESTFN(9)
102
103static void (*testfuncs[])(int)  = {
104	preemptirqtest_0,
105	preemptirqtest_1,
106	preemptirqtest_2,
107	preemptirqtest_3,
108	preemptirqtest_4,
109	preemptirqtest_5,
110	preemptirqtest_6,
111	preemptirqtest_7,
112	preemptirqtest_8,
113	preemptirqtest_9,
114};
115
116#define NR_TEST_FUNCS ARRAY_SIZE(testfuncs)
117
118static int preemptirq_delay_run(void *data)
119{
120	int i;
121	int s = MIN(burst_size, NR_TEST_FUNCS);
122	struct cpumask cpu_mask;
123
124	if (cpu_affinity > -1) {
125		cpumask_clear(&cpu_mask);
126		cpumask_set_cpu(cpu_affinity, &cpu_mask);
127		if (set_cpus_allowed_ptr(current, &cpu_mask))
128			pr_err("cpu_affinity:%d, failed\n", cpu_affinity);
129	}
130
131	for (i = 0; i < s; i++)
132		(testfuncs[i])(i);
133
134	complete(&done);
135
136	set_current_state(TASK_INTERRUPTIBLE);
137	while (!kthread_should_stop()) {
138		schedule();
139		set_current_state(TASK_INTERRUPTIBLE);
140	}
141
142	__set_current_state(TASK_RUNNING);
143
144	return 0;
145}
146
147static int preemptirq_run_test(void)
148{
149	struct task_struct *task;
150	char task_name[50];
151
152	init_completion(&done);
153
154	snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
155	task =  kthread_run(preemptirq_delay_run, NULL, task_name);
156	if (IS_ERR(task))
157		return PTR_ERR(task);
158	if (task) {
159		wait_for_completion(&done);
160		kthread_stop(task);
161	}
162	return 0;
163}
164
165
166static ssize_t trigger_store(struct kobject *kobj, struct kobj_attribute *attr,
167			 const char *buf, size_t count)
168{
169	ssize_t ret;
170
171	ret = preemptirq_run_test();
172	if (ret)
173		return ret;
174	return count;
175}
176
177static struct kobj_attribute trigger_attribute =
178	__ATTR(trigger, 0200, NULL, trigger_store);
179
180static struct attribute *attrs[] = {
181	&trigger_attribute.attr,
182	NULL,
183};
184
185static struct attribute_group attr_group = {
186	.attrs = attrs,
187};
188
189static struct kobject *preemptirq_delay_kobj;
190
191static int __init preemptirq_delay_init(void)
192{
193	int retval;
194
195	retval = preemptirq_run_test();
196	if (retval != 0)
197		return retval;
198
199	preemptirq_delay_kobj = kobject_create_and_add("preemptirq_delay_test",
200						       kernel_kobj);
201	if (!preemptirq_delay_kobj)
202		return -ENOMEM;
203
204	retval = sysfs_create_group(preemptirq_delay_kobj, &attr_group);
205	if (retval)
206		kobject_put(preemptirq_delay_kobj);
207
208	return retval;
209}
210
211static void __exit preemptirq_delay_exit(void)
212{
213	kobject_put(preemptirq_delay_kobj);
214}
215
216module_init(preemptirq_delay_init)
217module_exit(preemptirq_delay_exit)
218MODULE_LICENSE("GPL v2");
219