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 simple_thread_func(int cnt)
  23 {
  24         int array[6];
  25         int len = cnt % 5;
  26         int i;
  27
  28         set_current_state(TASK_INTERRUPTIBLE);
  29         schedule_timeout(HZ);
  30
  31         for (i = 0; i < len; i++)
  32                 array[i] = i + 1;
  33         array[i] = 0;
  34
  35         /* Silly tracepoints */
  36         trace_foo_bar("hello", cnt, array, random_strings[len],
  37                       &current->cpus_allowed);
  38
  39         trace_foo_with_template_simple("HELLO", cnt);
  40
  41         trace_foo_bar_with_cond("Some times print", cnt);
  42
  43         trace_foo_with_template_cond("prints other times", cnt);
  44
  45         trace_foo_with_template_print("I have to be different", cnt);
  46 }
  47
  48 static int simple_thread(void *arg)
  49 {
  50         int cnt = 0;
  51
  52         while (!kthread_should_stop())
  53                 simple_thread_func(cnt++);
  54
  55         return 0;
  56 }
  57
  58 static struct task_struct *simple_tsk;
  59 static struct task_struct *simple_tsk_fn;
  60
  61 static void simple_thread_func_fn(int cnt)
  62 {
  63         set_current_state(TASK_INTERRUPTIBLE);
  64         schedule_timeout(HZ);
  65
  66         /* More silly tracepoints */
  67         trace_foo_bar_with_fn("Look at me", cnt);
  68         trace_foo_with_template_fn("Look at me too", cnt);
  69 }
  70
  71 static int simple_thread_fn(void *arg)
  72 {
  73         int cnt = 0;
  74
  75         while (!kthread_should_stop())
  76                 simple_thread_func_fn(cnt++);
  77
  78         return 0;
  79 }
  80
  81 static DEFINE_MUTEX(thread_mutex);
  82 static int simple_thread_cnt;
  83
  84 int foo_bar_reg(void)
  85 {
  86         mutex_lock(&thread_mutex);
  87         if (simple_thread_cnt++)
  88                 goto out;
  89
  90         pr_info("Starting thread for foo_bar_fn\n");
  91         /*
  92          * We shouldn't be able to start a trace when the module is
  93          * unloading (there's other locks to prevent that). But
  94          * for consistency sake, we still take the thread_mutex.
  95          */
  96         simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
  97  out:
  98         mutex_unlock(&thread_mutex);
  99         return 0;
 100 }
 101
 102 void foo_bar_unreg(void)
 103 {
 104         mutex_lock(&thread_mutex);
 105         if (--simple_thread_cnt)
 106                 goto out;
 107
 108         pr_info("Killing thread for foo_bar_fn\n");
 109         if (simple_tsk_fn)
 110                 kthread_stop(simple_tsk_fn);
 111         simple_tsk_fn = NULL;
 112  out:
 113         mutex_unlock(&thread_mutex);
 114 }
 115
 116 static int __init trace_event_init(void)
 117 {
 118         simple_tsk = kthread_run(simple_thread, NULL, "event-sample");
 119         if (IS_ERR(simple_tsk))
 120                 return -1;
 121
 122         return 0;
 123 }
 124
 125 static void __exit trace_event_exit(void)
 126 {
 127         kthread_stop(simple_tsk);
 128         mutex_lock(&thread_mutex);
 129         if (simple_tsk_fn)
 130                 kthread_stop(simple_tsk_fn);
 131         simple_tsk_fn = NULL;
 132         mutex_unlock(&thread_mutex);
 133 }
 134
 135 module_init(trace_event_init);
 136 module_exit(trace_event_exit);
 137
 138 MODULE_AUTHOR("Steven Rostedt");
 139 MODULE_DESCRIPTION("trace-events-sample");
 140 MODULE_LICENSE("GPL");