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 int ltt_probe_register(struct lttng_probe_desc *desc)
  34 {
  35         int ret = 0;
  36         int i;
  37
  38         mutex_lock(&probe_mutex);
  39         /*
  40          * TODO: This is O(N^2). Turn into a hash table when probe registration
  41          * overhead becomes an issue.
  42          */
  43         for (i = 0; i < desc->nr_events; i++) {
  44                 if (find_event(desc->event_desc[i].name)) {
  45                         ret = -EEXIST;
  46                         goto end;
  47                 }
  48         }
  49         list_add(&desc->head, &probe_list);
  50 end:
  51         mutex_unlock(&probe_mutex);
  52         return ret;
  53 }
  54 EXPORT_SYMBOL_GPL(ltt_probe_register);
  55
  56 void ltt_probe_unregister(struct lttng_probe_desc *desc)
  57 {
  58         mutex_lock(&probe_mutex);
  59         list_del(&desc->head);
  60         mutex_unlock(&probe_mutex);
  61 }
  62 EXPORT_SYMBOL_GPL(ltt_probe_unregister);
  63
  64 const struct lttng_event_desc *ltt_event_get(const char *name)
  65 {
  66         const struct lttng_event_desc *event;
  67         int ret;
  68
  69         mutex_lock(&probe_mutex);
  70         event = find_event(name);
  71         mutex_unlock(&probe_mutex);
  72         if (!event)
  73                 return NULL;
  74         ret = try_module_get(event->owner);
  75         WARN_ON_ONCE(!ret);
  76         return event;
  77 }
  78 EXPORT_SYMBOL_GPL(ltt_event_get);
  79
  80 void ltt_event_put(const struct lttng_event_desc *event)
  81 {
  82         module_put(event->owner);
  83 }
  84 EXPORT_SYMBOL_GPL(ltt_event_put);