// SPDX-License-Identifier: GPL-2.0
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/*
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* Preempt / IRQ disable delay thread to test latency tracers
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*
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* Copyright (C) 2018 Joel Fernandes (Google) <joel@joelfernandes.org>
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*/
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#include <linux/trace_clock.h>
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#include <linux/delay.h>
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#include <linux/interrupt.h>
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#include <linux/irq.h>
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#include <linux/kernel.h>
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#include <linux/kthread.h>
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#include <linux/module.h>
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#include <linux/printk.h>
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#include <linux/string.h>
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static ulong delay = 100;
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static char test_mode[10] = "irq";
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module_param_named(delay, delay, ulong, S_IRUGO);
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module_param_string(test_mode, test_mode, 10, S_IRUGO);
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MODULE_PARM_DESC(delay, "Period in microseconds (100 uS default)");
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MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt or irq (default irq)");
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static void busy_wait(ulong time)
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{
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u64 start, end;
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start = trace_clock_local();
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do {
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end = trace_clock_local();
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if (kthread_should_stop())
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break;
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} while ((end - start) < (time * 1000));
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}
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static int preemptirq_delay_run(void *data)
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{
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unsigned long flags;
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if (!strcmp(test_mode, "irq")) {
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local_irq_save(flags);
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busy_wait(delay);
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local_irq_restore(flags);
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} else if (!strcmp(test_mode, "preempt")) {
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preempt_disable();
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busy_wait(delay);
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preempt_enable();
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}
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return 0;
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}
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static int __init preemptirq_delay_init(void)
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{
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char task_name[50];
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struct task_struct *test_task;
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snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
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test_task = kthread_run(preemptirq_delay_run, NULL, task_name);
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return PTR_ERR_OR_ZERO(test_task);
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}
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static void __exit preemptirq_delay_exit(void)
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{
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return;
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}
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module_init(preemptirq_delay_init)
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module_exit(preemptirq_delay_exit)
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MODULE_LICENSE("GPL v2");
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