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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/delay.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/ktime.h>
#include <linux/module.h>
#include <linux/printk.h>
#include <linux/string.h>
static ulong delay = 100;
static char test_mode[10] = "irq";
module_param_named(delay, delay, ulong, S_IRUGO);
module_param_string(test_mode, test_mode, 10, S_IRUGO);
MODULE_PARM_DESC(delay, "Period in microseconds (100 uS default)");
MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt or irq (default irq)");
static void busy_wait(ulong time)
{
ktime_t start, end;
start = ktime_get();
do {
end = ktime_get();
if (kthread_should_stop())
break;
} while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000));
}
static int preemptirq_delay_run(void *data)
{
unsigned long flags;
if (!strcmp(test_mode, "irq")) {
local_irq_save(flags);
busy_wait(delay);
local_irq_restore(flags);
} else if (!strcmp(test_mode, "preempt")) {
preempt_disable();
busy_wait(delay);
preempt_enable();
}
return 0;
}
static int __init preemptirq_delay_init(void)
{
char task_name[50];
struct task_struct *test_task;
snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
test_task = kthread_run(preemptirq_delay_run, NULL, task_name);
return PTR_ERR_OR_ZERO(test_task);
}
static void __exit preemptirq_delay_exit(void)
{
return;
}
module_init(preemptirq_delay_init)
module_exit(preemptirq_delay_exit)
MODULE_LICENSE("GPL v2");
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