// 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/kobject.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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#include <linux/sysfs.h>
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#include <linux/completion.h>
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static ulong delay = 100;
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static char test_mode[12] = "irq";
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static uint burst_size = 1;
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module_param_named(delay, delay, ulong, 0444);
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module_param_string(test_mode, test_mode, 12, 0444);
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module_param_named(burst_size, burst_size, uint, 0444);
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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, irq, or alternate (default irq)");
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MODULE_PARM_DESC(burst_size, "The size of a burst (default 1)");
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static struct completion done;
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#define MIN(x, y) ((x) < (y) ? (x) : (y))
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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 __always_inline void irqoff_test(void)
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{
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unsigned long flags;
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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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}
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static __always_inline void preemptoff_test(void)
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{
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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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static void execute_preemptirqtest(int idx)
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{
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if (!strcmp(test_mode, "irq"))
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irqoff_test();
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else if (!strcmp(test_mode, "preempt"))
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preemptoff_test();
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else if (!strcmp(test_mode, "alternate")) {
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if (idx % 2 == 0)
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irqoff_test();
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else
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preemptoff_test();
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}
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}
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#define DECLARE_TESTFN(POSTFIX) \
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static void preemptirqtest_##POSTFIX(int idx) \
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{ \
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execute_preemptirqtest(idx); \
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} \
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/*
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* We create 10 different functions, so that we can get 10 different
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* backtraces.
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*/
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DECLARE_TESTFN(0)
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DECLARE_TESTFN(1)
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DECLARE_TESTFN(2)
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DECLARE_TESTFN(3)
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DECLARE_TESTFN(4)
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DECLARE_TESTFN(5)
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DECLARE_TESTFN(6)
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DECLARE_TESTFN(7)
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DECLARE_TESTFN(8)
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DECLARE_TESTFN(9)
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static void (*testfuncs[])(int) = {
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preemptirqtest_0,
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preemptirqtest_1,
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preemptirqtest_2,
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preemptirqtest_3,
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preemptirqtest_4,
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preemptirqtest_5,
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preemptirqtest_6,
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preemptirqtest_7,
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preemptirqtest_8,
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preemptirqtest_9,
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};
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#define NR_TEST_FUNCS ARRAY_SIZE(testfuncs)
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static int preemptirq_delay_run(void *data)
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{
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int i;
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int s = MIN(burst_size, NR_TEST_FUNCS);
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for (i = 0; i < s; i++)
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(testfuncs[i])(i);
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complete(&done);
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set_current_state(TASK_INTERRUPTIBLE);
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while (!kthread_should_stop()) {
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schedule();
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set_current_state(TASK_INTERRUPTIBLE);
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}
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__set_current_state(TASK_RUNNING);
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return 0;
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}
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static int preemptirq_run_test(void)
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{
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struct task_struct *task;
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char task_name[50];
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init_completion(&done);
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snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
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task = kthread_run(preemptirq_delay_run, NULL, task_name);
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if (IS_ERR(task))
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return PTR_ERR(task);
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if (task) {
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wait_for_completion(&done);
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kthread_stop(task);
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}
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return 0;
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}
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static ssize_t trigger_store(struct kobject *kobj, struct kobj_attribute *attr,
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const char *buf, size_t count)
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{
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ssize_t ret;
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ret = preemptirq_run_test();
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if (ret)
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return ret;
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return count;
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}
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static struct kobj_attribute trigger_attribute =
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__ATTR(trigger, 0200, NULL, trigger_store);
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static struct attribute *attrs[] = {
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&trigger_attribute.attr,
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NULL,
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};
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static struct attribute_group attr_group = {
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.attrs = attrs,
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};
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static struct kobject *preemptirq_delay_kobj;
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static int __init preemptirq_delay_init(void)
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{
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int retval;
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retval = preemptirq_run_test();
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if (retval != 0)
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return retval;
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preemptirq_delay_kobj = kobject_create_and_add("preemptirq_delay_test",
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kernel_kobj);
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if (!preemptirq_delay_kobj)
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return -ENOMEM;
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retval = sysfs_create_group(preemptirq_delay_kobj, &attr_group);
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if (retval)
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kobject_put(preemptirq_delay_kobj);
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return retval;
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}
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static void __exit preemptirq_delay_exit(void)
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{
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kobject_put(preemptirq_delay_kobj);
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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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