// 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/kthread.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) { u64 start, end; start = trace_clock_local(); do { end = trace_clock_local(); if (kthread_should_stop()) break; } while ((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");