kernel/trace/preemptirq_delay_test.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Preempt / IRQ disable delay thread to test latency tracers
0004  *
0005  * Copyright (C) 2018 Joel Fernandes (Google) <joel@joelfernandes.org>
0006  */
0007
0008 #include <linux/trace_clock.h>
0009 #include <linux/delay.h>
0010 #include <linux/interrupt.h>
0011 #include <linux/irq.h>
0012 #include <linux/kernel.h>
0013 #include <linux/kobject.h>
0014 #include <linux/kthread.h>
0015 #include <linux/module.h>
0016 #include <linux/printk.h>
0017 #include <linux/string.h>
0018 #include <linux/sysfs.h>
0019 #include <linux/completion.h>
0020
0021 static ulong delay = 100;
0022 static char test_mode[12] = "irq";
0023 static uint burst_size = 1;
0024 static int  cpu_affinity = -1;
0025
0026 module_param_named(delay, delay, ulong, 0444);
0027 module_param_string(test_mode, test_mode, 12, 0444);
0028 module_param_named(burst_size, burst_size, uint, 0444);
0029 module_param_named(cpu_affinity, cpu_affinity, int, 0444);
0030 MODULE_PARM_DESC(delay, "Period in microseconds (100 us default)");
0031 MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt, irq, or alternate (default irq)");
0032 MODULE_PARM_DESC(burst_size, "The size of a burst (default 1)");
0033 MODULE_PARM_DESC(cpu_affinity, "Cpu num test is running on");
0034
0035 static struct completion done;
0036
0037 #define MIN(x, y) ((x) < (y) ? (x) : (y))
0038
0039 static void busy_wait(ulong time)
0040 {
0041     u64 start, end;
0042
0043     start = trace_clock_local();
0044
0045     do {
0046         end = trace_clock_local();
0047         if (kthread_should_stop())
0048             break;
0049     } while ((end - start) < (time * 1000));
0050 }
0051
0052 static __always_inline void irqoff_test(void)
0053 {
0054     unsigned long flags;
0055
0056     local_irq_save(flags);
0057     busy_wait(delay);
0058     local_irq_restore(flags);
0059 }
0060
0061 static __always_inline void preemptoff_test(void)
0062 {
0063     preempt_disable();
0064     busy_wait(delay);
0065     preempt_enable();
0066 }
0067
0068 static void execute_preemptirqtest(int idx)
0069 {
0070     if (!strcmp(test_mode, "irq"))
0071         irqoff_test();
0072     else if (!strcmp(test_mode, "preempt"))
0073         preemptoff_test();
0074     else if (!strcmp(test_mode, "alternate")) {
0075         if (idx % 2 == 0)
0076             irqoff_test();
0077         else
0078             preemptoff_test();
0079     }
0080 }
0081
0082 #define DECLARE_TESTFN(POSTFIX)             \
0083     static void preemptirqtest_##POSTFIX(int idx)   \
0084     {                       \
0085         execute_preemptirqtest(idx);        \
0086     }                       \
0087
0088 /*
0089  * We create 10 different functions, so that we can get 10 different
0090  * backtraces.
0091  */
0092 DECLARE_TESTFN(0)
0093 DECLARE_TESTFN(1)
0094 DECLARE_TESTFN(2)
0095 DECLARE_TESTFN(3)
0096 DECLARE_TESTFN(4)
0097 DECLARE_TESTFN(5)
0098 DECLARE_TESTFN(6)
0099 DECLARE_TESTFN(7)
0100 DECLARE_TESTFN(8)
0101 DECLARE_TESTFN(9)
0102
0103 static void (*testfuncs[])(int)  = {
0104     preemptirqtest_0,
0105     preemptirqtest_1,
0106     preemptirqtest_2,
0107     preemptirqtest_3,
0108     preemptirqtest_4,
0109     preemptirqtest_5,
0110     preemptirqtest_6,
0111     preemptirqtest_7,
0112     preemptirqtest_8,
0113     preemptirqtest_9,
0114 };
0115
0116 #define NR_TEST_FUNCS ARRAY_SIZE(testfuncs)
0117
0118 static int preemptirq_delay_run(void *data)
0119 {
0120     int i;
0121     int s = MIN(burst_size, NR_TEST_FUNCS);
0122     struct cpumask cpu_mask;
0123
0124     if (cpu_affinity > -1) {
0125         cpumask_clear(&cpu_mask);
0126         cpumask_set_cpu(cpu_affinity, &cpu_mask);
0127         if (set_cpus_allowed_ptr(current, &cpu_mask))
0128             pr_err("cpu_affinity:%d, failed\n", cpu_affinity);
0129     }
0130
0131     for (i = 0; i < s; i++)
0132         (testfuncs[i])(i);
0133
0134     complete(&done);
0135
0136     set_current_state(TASK_INTERRUPTIBLE);
0137     while (!kthread_should_stop()) {
0138         schedule();
0139         set_current_state(TASK_INTERRUPTIBLE);
0140     }
0141
0142     __set_current_state(TASK_RUNNING);
0143
0144     return 0;
0145 }
0146
0147 static int preemptirq_run_test(void)
0148 {
0149     struct task_struct *task;
0150     char task_name[50];
0151
0152     init_completion(&done);
0153
0154     snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
0155     task =  kthread_run(preemptirq_delay_run, NULL, task_name);
0156     if (IS_ERR(task))
0157         return PTR_ERR(task);
0158     if (task) {
0159         wait_for_completion(&done);
0160         kthread_stop(task);
0161     }
0162     return 0;
0163 }
0164
0165
0166 static ssize_t trigger_store(struct kobject *kobj, struct kobj_attribute *attr,
0167              const char *buf, size_t count)
0168 {
0169     ssize_t ret;
0170
0171     ret = preemptirq_run_test();
0172     if (ret)
0173         return ret;
0174     return count;
0175 }
0176
0177 static struct kobj_attribute trigger_attribute =
0178     __ATTR(trigger, 0200, NULL, trigger_store);
0179
0180 static struct attribute *attrs[] = {
0181     &trigger_attribute.attr,
0182     NULL,
0183 };
0184
0185 static struct attribute_group attr_group = {
0186     .attrs = attrs,
0187 };
0188
0189 static struct kobject *preemptirq_delay_kobj;
0190
0191 static int __init preemptirq_delay_init(void)
0192 {
0193     int retval;
0194
0195     retval = preemptirq_run_test();
0196     if (retval != 0)
0197         return retval;
0198
0199     preemptirq_delay_kobj = kobject_create_and_add("preemptirq_delay_test",
0200                                kernel_kobj);
0201     if (!preemptirq_delay_kobj)
0202         return -ENOMEM;
0203
0204     retval = sysfs_create_group(preemptirq_delay_kobj, &attr_group);
0205     if (retval)
0206         kobject_put(preemptirq_delay_kobj);
0207
0208     return retval;
0209 }
0210
0211 static void __exit preemptirq_delay_exit(void)
0212 {
0213     kobject_put(preemptirq_delay_kobj);
0214 }
0215
0216 module_init(preemptirq_delay_init)
0217 module_exit(preemptirq_delay_exit)
0218 MODULE_LICENSE("GPL v2");