1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
|
// SPDX-License-Identifier: GPL-2.0
/*
* Preempt / IRQ disable delay thread to test latency tracers
*
* Copyright (C) 2018 Joel Fernandes (Google) <joel@joelfernandes.org>
*/
#include <linux/trace_clock.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/kobject.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/printk.h>
#include <linux/string.h>
#include <linux/sysfs.h>
#include <linux/completion.h>
static ulong delay = 100;
static char test_mode[12] = "irq";
static uint burst_size = 1;
static int cpu_affinity = -1;
module_param_named(delay, delay, ulong, 0444);
module_param_string(test_mode, test_mode, 12, 0444);
module_param_named(burst_size, burst_size, uint, 0444);
module_param_named(cpu_affinity, cpu_affinity, int, 0444);
MODULE_PARM_DESC(delay, "Period in microseconds (100 us default)");
MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt, irq, or alternate (default irq)");
MODULE_PARM_DESC(burst_size, "The size of a burst (default 1)");
MODULE_PARM_DESC(cpu_affinity, "Cpu num test is running on");
static struct completion done;
#define MIN(x, y) ((x) < (y) ? (x) : (y))
static void busy_wait(ulong time)
{
u64 start, end;
start = trace_clock_local();
do {
end = trace_clock_local();
if (kthread_should_stop())
break;
} while ((end - start) < (time * 1000));
}
static __always_inline void irqoff_test(void)
{
unsigned long flags;
local_irq_save(flags);
busy_wait(delay);
local_irq_restore(flags);
}
static __always_inline void preemptoff_test(void)
{
preempt_disable();
busy_wait(delay);
preempt_enable();
}
static void execute_preemptirqtest(int idx)
{
if (!strcmp(test_mode, "irq"))
irqoff_test();
else if (!strcmp(test_mode, "preempt"))
preemptoff_test();
else if (!strcmp(test_mode, "alternate")) {
if (idx % 2 == 0)
irqoff_test();
else
preemptoff_test();
}
}
#define DECLARE_TESTFN(POSTFIX) \
static void preemptirqtest_##POSTFIX(int idx) \
{ \
execute_preemptirqtest(idx); \
} \
/*
* We create 10 different functions, so that we can get 10 different
* backtraces.
*/
DECLARE_TESTFN(0)
DECLARE_TESTFN(1)
DECLARE_TESTFN(2)
DECLARE_TESTFN(3)
DECLARE_TESTFN(4)
DECLARE_TESTFN(5)
DECLARE_TESTFN(6)
DECLARE_TESTFN(7)
DECLARE_TESTFN(8)
DECLARE_TESTFN(9)
static void (*testfuncs[])(int) = {
preemptirqtest_0,
preemptirqtest_1,
preemptirqtest_2,
preemptirqtest_3,
preemptirqtest_4,
preemptirqtest_5,
preemptirqtest_6,
preemptirqtest_7,
preemptirqtest_8,
preemptirqtest_9,
};
#define NR_TEST_FUNCS ARRAY_SIZE(testfuncs)
static int preemptirq_delay_run(void *data)
{
int i;
int s = MIN(burst_size, NR_TEST_FUNCS);
struct cpumask cpu_mask;
if (cpu_affinity > -1) {
cpumask_clear(&cpu_mask);
cpumask_set_cpu(cpu_affinity, &cpu_mask);
if (set_cpus_allowed_ptr(current, &cpu_mask))
pr_err("cpu_affinity:%d, failed\n", cpu_affinity);
}
for (i = 0; i < s; i++)
(testfuncs[i])(i);
complete(&done);
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
schedule();
set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
return 0;
}
static int preemptirq_run_test(void)
{
struct task_struct *task;
char task_name[50];
init_completion(&done);
snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
task = kthread_run(preemptirq_delay_run, NULL, task_name);
if (IS_ERR(task))
return PTR_ERR(task);
if (task) {
wait_for_completion(&done);
kthread_stop(task);
}
return 0;
}
static ssize_t trigger_store(struct kobject *kobj, struct kobj_attribute *attr,
const char *buf, size_t count)
{
ssize_t ret;
ret = preemptirq_run_test();
if (ret)
return ret;
return count;
}
static struct kobj_attribute trigger_attribute =
__ATTR(trigger, 0200, NULL, trigger_store);
static struct attribute *attrs[] = {
&trigger_attribute.attr,
NULL,
};
static struct attribute_group attr_group = {
.attrs = attrs,
};
static struct kobject *preemptirq_delay_kobj;
static int __init preemptirq_delay_init(void)
{
int retval;
retval = preemptirq_run_test();
if (retval != 0)
return retval;
preemptirq_delay_kobj = kobject_create_and_add("preemptirq_delay_test",
kernel_kobj);
if (!preemptirq_delay_kobj)
return -ENOMEM;
retval = sysfs_create_group(preemptirq_delay_kobj, &attr_group);
if (retval)
kobject_put(preemptirq_delay_kobj);
return retval;
}
static void __exit preemptirq_delay_exit(void)
{
kobject_put(preemptirq_delay_kobj);
}
module_init(preemptirq_delay_init)
module_exit(preemptirq_delay_exit)
MODULE_DESCRIPTION("Preempt / IRQ disable delay thread to test latency tracers");
MODULE_LICENSE("GPL v2");
|