ltt-probes.c

   1 /*
   2  * ltt-probes.c
   3  *
   4  * Copyright 2010 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Holds LTTng probes registry.
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/list.h>
  11 #include <linux/mutex.h>
  12
  13 #include "ltt-events.h"
  14
  15 static LIST_HEAD(probe_list);
  16 static DEFINE_MUTEX(probe_mutex);
  17
  18 static
  19 const struct lttng_event_desc *find_event(const char *name)
  20 {
  21         struct lttng_probe_desc *probe_desc;
  22         int i;
  23
  24         list_for_each_entry(probe_desc, &probe_list, head) {
  25                 for (i = 0; i < probe_desc->nr_events; i++) {
  26                         if (!strcmp(probe_desc->event_desc[i].name, name))
  27                                 return &probe_desc->event_desc[i];
  28                 }
  29         }
  30         return NULL;
  31 }
  32
  33 /*
  34  * TODO: registration of probe descriptions in dynamically allocated memory (not
  35  * directly in a module memory) will require some care for refcounting: it's
  36  * currently done by just refcounting the module in event_get/put.
  37  */
  38 int ltt_probe_register(struct lttng_probe_desc *desc)
  39 {
  40         int ret = 0;
  41         int i;
  42
  43         mutex_lock(&probe_mutex);
  44         /*
  45          * TODO: This is O(N^2). Turn into a hash table when probe registration
  46          * overhead becomes an issue.
  47          */
  48         for (i = 0; i < desc->nr_events; i++) {
  49                 if (find_event(desc->event_desc[i].name)) {
  50                         ret = -EEXIST;
  51                         goto end;
  52                 }
  53         }
  54         list_add(&desc->head, &probe_list);
  55 end:
  56         mutex_unlock(&probe_mutex);
  57         return ret;
  58 }
  59 EXPORT_SYMBOL_GPL(ltt_probe_register);
  60
  61 void ltt_probe_unregister(struct lttng_probe_desc *desc)
  62 {
  63         mutex_lock(&probe_mutex);
  64         list_del(&desc->head);
  65         mutex_unlock(&probe_mutex);
  66 }
  67 EXPORT_SYMBOL_GPL(ltt_probe_unregister);
  68
  69 const struct lttng_event_desc *ltt_event_get(const char *name)
  70 {
  71         const struct lttng_event_desc *event;
  72         int ret;
  73
  74         mutex_lock(&probe_mutex);
  75         event = find_event(name);
  76         mutex_unlock(&probe_mutex);
  77         if (!event)
  78                 return NULL;
  79         ret = try_module_get(__module_text_address((unsigned long) event));
  80         WARN_ON_ONCE(!ret);
  81         return event;
  82 }
  83 EXPORT_SYMBOL_GPL(ltt_event_get);
  84
  85 void ltt_event_put(const struct lttng_event_desc *event)
  86 {
  87         module_put(__module_text_address((unsigned long) event));
  88 }
  89 EXPORT_SYMBOL_GPL(ltt_event_put);