samples/trace_events/trace-events-sample.c

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