kernel/trace/preemptirq_delay_test.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Preempt / IRQ disable delay thread to test latency tracers
   4  *
   5  * Copyright (C) 2018 Joel Fernandes (Google) <joel@joelfernandes.org>
   6  */
   7
   8 #include <linux/trace_clock.h>
   9 #include <linux/delay.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/irq.h>
  12 #include <linux/kernel.h>
  13 #include <linux/kobject.h>
  14 #include <linux/kthread.h>
  15 #include <linux/module.h>
  16 #include <linux/printk.h>
  17 #include <linux/string.h>
  18 #include <linux/sysfs.h>
  19 #include <linux/completion.h>
  20
  21 static ulong delay = 100;
  22 static char test_mode[12] = "irq";
  23 static uint burst_size = 1;
  24 static int  cpu_affinity = -1;
  25
  26 module_param_named(delay, delay, ulong, 0444);
  27 module_param_string(test_mode, test_mode, 12, 0444);
  28 module_param_named(burst_size, burst_size, uint, 0444);
  29 module_param_named(cpu_affinity, cpu_affinity, int, 0444);
  30 MODULE_PARM_DESC(delay, "Period in microseconds (100 us default)");
  31 MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt, irq, or alternate (default irq)");
  32 MODULE_PARM_DESC(burst_size, "The size of a burst (default 1)");
  33 MODULE_PARM_DESC(cpu_affinity, "Cpu num test is running on");
  34
  35 static struct completion done;
  36
  37 #define MIN(x, y) ((x) < (y) ? (x) : (y))
  38
  39 static void busy_wait(ulong time)
  40 {
  41         u64 start, end;
  42
  43         start = trace_clock_local();
  44
  45         do {
  46                 end = trace_clock_local();
  47                 if (kthread_should_stop())
  48                         break;
  49         } while ((end - start) < (time * 1000));
  50 }
  51
  52 static __always_inline void irqoff_test(void)
  53 {
  54         unsigned long flags;
  55
  56         local_irq_save(flags);
  57         busy_wait(delay);
  58         local_irq_restore(flags);
  59 }
  60
  61 static __always_inline void preemptoff_test(void)
  62 {
  63         preempt_disable();
  64         busy_wait(delay);
  65         preempt_enable();
  66 }
  67
  68 static void execute_preemptirqtest(int idx)
  69 {
  70         if (!strcmp(test_mode, "irq"))
  71                 irqoff_test();
  72         else if (!strcmp(test_mode, "preempt"))
  73                 preemptoff_test();
  74         else if (!strcmp(test_mode, "alternate")) {
  75                 if (idx % 2 == 0)
  76                         irqoff_test();
  77                 else
  78                         preemptoff_test();
  79         }
  80 }
  81
  82 #define DECLARE_TESTFN(POSTFIX)                         \
  83         static void preemptirqtest_##POSTFIX(int idx)   \
  84         {                                               \
  85                 execute_preemptirqtest(idx);            \
  86         }                                               \
  87
  88 /*
  89  * We create 10 different functions, so that we can get 10 different
  90  * backtraces.
  91  */
  92 DECLARE_TESTFN(0)
  93 DECLARE_TESTFN(1)
  94 DECLARE_TESTFN(2)
  95 DECLARE_TESTFN(3)
  96 DECLARE_TESTFN(4)
  97 DECLARE_TESTFN(5)
  98 DECLARE_TESTFN(6)
  99 DECLARE_TESTFN(7)
 100 DECLARE_TESTFN(8)
 101 DECLARE_TESTFN(9)
 102
 103 static void (*testfuncs[])(int)  = {
 104         preemptirqtest_0,
 105         preemptirqtest_1,
 106         preemptirqtest_2,
 107         preemptirqtest_3,
 108         preemptirqtest_4,
 109         preemptirqtest_5,
 110         preemptirqtest_6,
 111         preemptirqtest_7,
 112         preemptirqtest_8,
 113         preemptirqtest_9,
 114 };
 115
 116 #define NR_TEST_FUNCS ARRAY_SIZE(testfuncs)
 117
 118 static int preemptirq_delay_run(void *data)
 119 {
 120         int i;
 121         int s = MIN(burst_size, NR_TEST_FUNCS);
 122         struct cpumask cpu_mask;
 123
 124         if (cpu_affinity > -1) {
 125                 cpumask_clear(&cpu_mask);
 126                 cpumask_set_cpu(cpu_affinity, &cpu_mask);
 127                 if (set_cpus_allowed_ptr(current, &cpu_mask))
 128                         pr_err("cpu_affinity:%d, failed\n", cpu_affinity);
 129         }
 130
 131         for (i = 0; i < s; i++)
 132                 (testfuncs[i])(i);
 133
 134         complete(&done);
 135
 136         set_current_state(TASK_INTERRUPTIBLE);
 137         while (!kthread_should_stop()) {
 138                 schedule();
 139                 set_current_state(TASK_INTERRUPTIBLE);
 140         }
 141
 142         __set_current_state(TASK_RUNNING);
 143
 144         return 0;
 145 }
 146
 147 static int preemptirq_run_test(void)
 148 {
 149         struct task_struct *task;
 150         char task_name[50];
 151
 152         init_completion(&done);
 153
 154         snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
 155         task =  kthread_run(preemptirq_delay_run, NULL, task_name);
 156         if (IS_ERR(task))
 157                 return PTR_ERR(task);
 158         if (task) {
 159                 wait_for_completion(&done);
 160                 kthread_stop(task);
 161         }
 162         return 0;
 163 }
 164
 165
 166 static ssize_t trigger_store(struct kobject *kobj, struct kobj_attribute *attr,
 167                          const char *buf, size_t count)
 168 {
 169         ssize_t ret;
 170
 171         ret = preemptirq_run_test();
 172         if (ret)
 173                 return ret;
 174         return count;
 175 }
 176
 177 static struct kobj_attribute trigger_attribute =
 178         __ATTR(trigger, 0200, NULL, trigger_store);
 179
 180 static struct attribute *attrs[] = {
 181         &trigger_attribute.attr,
 182         NULL,
 183 };
 184
 185 static struct attribute_group attr_group = {
 186         .attrs = attrs,
 187 };
 188
 189 static struct kobject *preemptirq_delay_kobj;
 190
 191 static int __init preemptirq_delay_init(void)
 192 {
 193         int retval;
 194
 195         retval = preemptirq_run_test();
 196         if (retval != 0)
 197                 return retval;
 198
 199         preemptirq_delay_kobj = kobject_create_and_add("preemptirq_delay_test",
 200                                                        kernel_kobj);
 201         if (!preemptirq_delay_kobj)
 202                 return -ENOMEM;
 203
 204         retval = sysfs_create_group(preemptirq_delay_kobj, &attr_group);
 205         if (retval)
 206                 kobject_put(preemptirq_delay_kobj);
 207
 208         return retval;
 209 }
 210
 211 static void __exit preemptirq_delay_exit(void)
 212 {
 213         kobject_put(preemptirq_delay_kobj);
 214 }
 215
 216 module_init(preemptirq_delay_init)
 217 module_exit(preemptirq_delay_exit)
 218 MODULE_LICENSE("GPL v2");