samples/trace_events/trace-events-sample.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/module.h>
   3 #include <linux/kthread.h>
   4
   5 /*
   6  * Any file that uses trace points, must include the header.
   7  * But only one file, must include the header by defining
   8  * CREATE_TRACE_POINTS first.  This will make the C code that
   9  * creates the handles for the trace points.
  10  */
  11 #define CREATE_TRACE_POINTS
  12 #include "trace-events-sample.h"
  13
  14 static const char *random_strings[] = {
  15         "Mother Goose",
  16         "Snoopy",
  17         "Gandalf",
  18         "Frodo",
  19         "One ring to rule them all"
  20 };
  21
  22 static void do_simple_thread_func(int cnt, const char *fmt, ...)
  23 {
  24         unsigned long bitmask[1] = {0xdeadbeefUL};
  25         va_list va;
  26         int array[6];
  27         int len = cnt % 5;
  28         int i;
  29
  30         set_current_state(TASK_INTERRUPTIBLE);
  31         schedule_timeout(HZ);
  32
  33         for (i = 0; i < len; i++)
  34                 array[i] = i + 1;
  35         array[i] = 0;
  36
  37         va_start(va, fmt);
  38
  39         /* Silly tracepoints */
  40         trace_foo_bar("hello", cnt, array, random_strings[len],
  41                       current->cpus_ptr, fmt, &va);
  42
  43         va_end(va);
  44
  45         trace_foo_with_template_simple("HELLO", cnt);
  46
  47         trace_foo_bar_with_cond("Some times print", cnt);
  48
  49         trace_foo_with_template_cond("prints other times", cnt);
  50
  51         trace_foo_with_template_print("I have to be different", cnt);
  52
  53         trace_foo_rel_loc("Hello __rel_loc", cnt, bitmask, current->cpus_ptr);
  54 }
  55
  56 static void simple_thread_func(int cnt)
  57 {
  58         do_simple_thread_func(cnt, "iter=%d", cnt);
  59 }
  60
  61 static int simple_thread(void *arg)
  62 {
  63         int cnt = 0;
  64
  65         while (!kthread_should_stop())
  66                 simple_thread_func(cnt++);
  67
  68         return 0;
  69 }
  70
  71 static struct task_struct *simple_tsk;
  72 static struct task_struct *simple_tsk_fn;
  73
  74 static void simple_thread_func_fn(int cnt)
  75 {
  76         set_current_state(TASK_INTERRUPTIBLE);
  77         schedule_timeout(HZ);
  78
  79         /* More silly tracepoints */
  80         trace_foo_bar_with_fn("Look at me", cnt);
  81         trace_foo_with_template_fn("Look at me too", cnt);
  82 }
  83
  84 static int simple_thread_fn(void *arg)
  85 {
  86         int cnt = 0;
  87
  88         while (!kthread_should_stop())
  89                 simple_thread_func_fn(cnt++);
  90
  91         return 0;
  92 }
  93
  94 static DEFINE_MUTEX(thread_mutex);
  95 static int simple_thread_cnt;
  96
  97 int foo_bar_reg(void)
  98 {
  99         mutex_lock(&thread_mutex);
 100         if (simple_thread_cnt++)
 101                 goto out;
 102
 103         pr_info("Starting thread for foo_bar_fn\n");
 104         /*
 105          * We shouldn't be able to start a trace when the module is
 106          * unloading (there's other locks to prevent that). But
 107          * for consistency sake, we still take the thread_mutex.
 108          */
 109         simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
 110  out:
 111         mutex_unlock(&thread_mutex);
 112         return 0;
 113 }
 114
 115 void foo_bar_unreg(void)
 116 {
 117         mutex_lock(&thread_mutex);
 118         if (--simple_thread_cnt)
 119                 goto out;
 120
 121         pr_info("Killing thread for foo_bar_fn\n");
 122         if (simple_tsk_fn)
 123                 kthread_stop(simple_tsk_fn);
 124         simple_tsk_fn = NULL;
 125  out:
 126         mutex_unlock(&thread_mutex);
 127 }
 128
 129 static int __init trace_event_init(void)
 130 {
 131         simple_tsk = kthread_run(simple_thread, NULL, "event-sample");
 132         if (IS_ERR(simple_tsk))
 133                 return -1;
 134
 135         return 0;
 136 }
 137
 138 static void __exit trace_event_exit(void)
 139 {
 140         kthread_stop(simple_tsk);
 141         mutex_lock(&thread_mutex);
 142         if (simple_tsk_fn)
 143                 kthread_stop(simple_tsk_fn);
 144         simple_tsk_fn = NULL;
 145         mutex_unlock(&thread_mutex);
 146 }
 147
 148 module_init(trace_event_init);
 149 module_exit(trace_event_exit);
 150
 151 MODULE_AUTHOR("Steven Rostedt");
 152 MODULE_DESCRIPTION("trace-events-sample");
 153 MODULE_LICENSE("GPL");