LXR linux/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
  13static const char *random_strings[] = {
  14        "Mother Goose",
  15        "Snoopy",
  16        "Gandalf",
  17        "Frodo",
  18        "One ring to rule them all"
  19};
  20
  21static 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                      tsk_cpus_allowed(current));
  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
  47static 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
  57static struct task_struct *simple_tsk;
  58static struct task_struct *simple_tsk_fn;
  59
  60static 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
  70static 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
  80static DEFINE_MUTEX(thread_mutex);
  81
  82void foo_bar_reg(void)
  83{
  84        pr_info("Starting thread for foo_bar_fn\n");
  85        /*
  86         * We shouldn't be able to start a trace when the module is
  87         * unloading (there's other locks to prevent that). But
  88         * for consistency sake, we still take the thread_mutex.
  89         */
  90        mutex_lock(&thread_mutex);
  91        simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
  92        mutex_unlock(&thread_mutex);
  93}
  94
  95void foo_bar_unreg(void)
  96{
  97        pr_info("Killing thread for foo_bar_fn\n");
  98        /* protect against module unloading */
  99        mutex_lock(&thread_mutex);
 100        if (simple_tsk_fn)
 101                kthread_stop(simple_tsk_fn);
 102        simple_tsk_fn = NULL;
 103        mutex_unlock(&thread_mutex);
 104}
 105
 106static int __init trace_event_init(void)
 107{
 108        simple_tsk = kthread_run(simple_thread, NULL, "event-sample");
 109        if (IS_ERR(simple_tsk))
 110                return -1;
 111
 112        return 0;
 113}
 114
 115static void __exit trace_event_exit(void)
 116{
 117        kthread_stop(simple_tsk);
 118        mutex_lock(&thread_mutex);
 119        if (simple_tsk_fn)
 120                kthread_stop(simple_tsk_fn);
 121        simple_tsk_fn = NULL;
 122        mutex_unlock(&thread_mutex);
 123}
 124
 125module_init(trace_event_init);
 126module_exit(trace_event_exit);
 127
 128MODULE_AUTHOR("Steven Rostedt");
 129MODULE_DESCRIPTION("trace-events-sample");
 130MODULE_LICENSE("GPL");
 131