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