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// 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>
static ulong delay = 100;
static char test_mode[12] = "irq";
static uint burst_size = 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_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)");
#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);
for (i = 0; i < s; i++)
(testfuncs[i])(i);
return 0;
}
static struct task_struct *preemptirq_start_test(void)
{
char task_name[50];
snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
return kthread_run(preemptirq_delay_run, NULL, task_name);
}
static ssize_t trigger_store(struct kobject *kobj, struct kobj_attribute *attr,
const char *buf, size_t count)
{
preemptirq_start_test();
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)
{
struct task_struct *test_task;
int retval;
test_task = preemptirq_start_test();
retval = PTR_ERR_OR_ZERO(test_task);
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_LICENSE("GPL v2");
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