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