ltt-events.c

   1 /*
   2  * ltt-events.c
   3  *
   4  * Copyright 2010 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Holds LTTng per-session event registry.
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/list.h>
  11 #include <linux/mutex.h>
  12 #include <linux/sched.h>
  13 #include <linux/slab.h>
  14 #include <linux/vmalloc.h>      /* For vmalloc_sync_all */
  15 #include "ltt-events.h"
  16
  17 static LIST_HEAD(sessions);
  18 static LIST_HEAD(ltt_transport_list);
  19 static DEFINE_MUTEX(sessions_mutex);
  20 static struct kmem_cache *event_cache;
  21
  22 static void synchronize_trace(void)
  23 {
  24         synchronize_sched();
  25 #ifdef CONFIG_PREEMPT_RT
  26         synchronize_rcu();
  27 #endif
  28 }
  29
  30 struct ltt_session *ltt_session_create(void)
  31 {
  32         struct ltt_session *session;
  33
  34         mutex_lock(&sessions_mutex);
  35         session = kmalloc(sizeof(struct ltt_session), GFP_KERNEL);
  36         if (!session)
  37                 return NULL;
  38         INIT_LIST_HEAD(&session->chan);
  39         list_add(&session->list, &sessions);
  40         mutex_unlock(&sessions_mutex);
  41         return session;
  42 }
  43
  44 void ltt_session_destroy(struct ltt_session *session)
  45 {
  46         struct ltt_channel *chan, *tmpchan;
  47         struct ltt_event *event, *tmpevent;
  48
  49         mutex_lock(&sessions_mutex);
  50         session->active = 0;
  51         synchronize_trace();    /* Wait for in-flight events to complete */
  52         list_for_each_entry_safe(event, tmpevent, &session->events, list)
  53                 _ltt_event_destroy(event);
  54         list_for_each_entry_safe(chan, tmpchan, &session->chan, list)
  55                 _ltt_channel_destroy(chan);
  56         list_del(&session->list);
  57         mutex_unlock(&sessions_mutex);
  58         kfree(session);
  59 }
  60
  61 int ltt_session_start(struct ltt_session *session)
  62 {
  63         int ret = 0;
  64
  65         mutex_lock(&sessions_mutex);
  66         if (session->active) {
  67                 ret = -EBUSY;
  68                 goto end;
  69         }
  70         session->active = 1;
  71         synchronize_trace();    /* Wait for in-flight events to complete */
  72 end:
  73         mutex_unlock(&sessions_mutex);
  74         return ret;
  75 }
  76
  77 int ltt_session_stop(struct ltt_session *session)
  78 {
  79         int ret = 0;
  80
  81         mutex_lock(&sessions_mutex);
  82         if (!session->active) {
  83                 ret = -EBUSY;
  84                 goto end;
  85         }
  86         session->active = 0;
  87         synchronize_trace();    /* Wait for in-flight events to complete */
  88 end:
  89         mutex_unlock(&sessions_mutex);
  90         return ret;
  91 }
  92
  93 struct ltt_channel *ltt_channel_create(struct ltt_session *session,
  94                                        int overwrite, void *buf_addr,
  95                                        size_t subbuf_size, size_t num_subbuf,
  96                                        unsigned int switch_timer_interval,
  97                                        unsigned int read_timer_interval)
  98 {
  99         struct ltt_channel *chan;
 100         struct ltt_transport *transport = NULL, *tran_iter;
 101         char *transport_name;
 102
 103         mutex_lock(&sessions_mutex);
 104         if (session->active)
 105                 goto active;    /* Refuse to add channel to active session */
 106         transport_name = overwrite ? "relay-overwrite" : "relay-discard";
 107         list_for_each_entry(tran_iter, &ltt_transport_list, node) {
 108                 if (!strcmp(tran_iter->name, transport_name)) {
 109                         transport = tran_iter;
 110                         break;
 111                 }
 112         }
 113         if (!transport)
 114                 goto notransport;
 115         chan = kmalloc(sizeof(struct ltt_channel), GFP_KERNEL);
 116         if (!chan)
 117                 goto nomem;
 118         chan->session = session;
 119         init_waitqueue_head(&chan->notify_wait);
 120         chan->chan = transport->ops.channel_create("[lttng]", session, buf_addr,
 121                         subbuf_size, num_subbuf, switch_timer_interval,
 122                         read_timer_interval);
 123         chan->ops = &transport->ops;
 124         list_add(&chan->list, &session->chan);
 125         mutex_unlock(&sessions_mutex);
 126         return chan;
 127
 128 nomem:
 129 notransport:
 130 active:
 131         mutex_unlock(&sessions_mutex);
 132         return NULL;
 133 }
 134
 135 /*
 136  * Only used internally at session destruction.
 137  */
 138 void _ltt_channel_destroy(struct ltt_channel *chan)
 139 {
 140         chan->ops->channel_destroy(chan->chan);
 141         list_del(&chan->list);
 142         kfree(chan);
 143 }
 144
 145 /*
 146  * Supports event creation while tracing session is active.
 147  */
 148 struct ltt_event *ltt_event_create(struct ltt_channel *chan, char *name,
 149                                    enum instrum_type itype,
 150                                    void *probe, void *filter)
 151 {
 152         struct ltt_event *event;
 153         int ret;
 154
 155         mutex_lock(&sessions_mutex);
 156         if (chan->free_event_id == -1UL)
 157                 goto full;
 158         /*
 159          * This is O(n^2) (for each event loop called at event creation).
 160          * Might require a hash if we have lots of events.
 161          */
 162         list_for_each_entry(event, &chan->session->events, list)
 163                 if (!strcmp(event->name, name))
 164                         goto exist;
 165         event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
 166         if (!event)
 167                 goto cache_error;
 168         event->name = kmalloc(strlen(name) + 1, GFP_KERNEL);
 169         if (!event->name)
 170                 goto name_error;
 171         strcpy(event->name, name);
 172         event->chan = chan;
 173         event->probe = probe;
 174         event->filter = filter;
 175         event->id = chan->free_event_id++;
 176         event->itype = itype;
 177         /* Populate ltt_event structure before tracepoint registration. */
 178         smp_wmb();
 179         switch (itype) {
 180         case INSTRUM_TRACEPOINTS:
 181                 ret = tracepoint_probe_register(name, probe, event);
 182                 if (ret)
 183                         goto register_error;
 184                 break;
 185         default:
 186                 WARN_ON_ONCE(1);
 187         }
 188         mutex_unlock(&sessions_mutex);
 189         return event;
 190
 191 register_error:
 192         kfree(event->name);
 193 name_error:
 194         kmem_cache_free(event_cache, event);
 195 cache_error:
 196 exist:
 197 full:
 198         mutex_unlock(&sessions_mutex);
 199         return NULL;
 200 }
 201
 202 /*
 203  * Only used internally at session destruction.
 204  */
 205 int _ltt_event_destroy(struct ltt_event *event)
 206 {
 207         int ret = -EINVAL;
 208
 209         switch (event->itype) {
 210         case INSTRUM_TRACEPOINTS:
 211                 ret = tracepoint_probe_unregister(event->name, event->probe,
 212                                                   event);
 213                 if (ret)
 214                         return ret;
 215                 break;
 216         default:
 217                 WARN_ON_ONCE(1);
 218         }
 219         kfree(event->name);
 220         kmem_cache_free(event_cache, event);
 221         return ret;
 222 }
 223
 224 /**
 225  * ltt_transport_register - LTT transport registration
 226  * @transport: transport structure
 227  *
 228  * Registers a transport which can be used as output to extract the data out of
 229  * LTTng. The module calling this registration function must ensure that no
 230  * trap-inducing code will be executed by the transport functions. E.g.
 231  * vmalloc_sync_all() must be called between a vmalloc and the moment the memory
 232  * is made visible to the transport function. This registration acts as a
 233  * vmalloc_sync_all. Therefore, only if the module allocates virtual memory
 234  * after its registration must it synchronize the TLBs.
 235  */
 236 void ltt_transport_register(struct ltt_transport *transport)
 237 {
 238         /*
 239          * Make sure no page fault can be triggered by the module about to be
 240          * registered. We deal with this here so we don't have to call
 241          * vmalloc_sync_all() in each module's init.
 242          */
 243         vmalloc_sync_all();
 244
 245         mutex_lock(&sessions_mutex);
 246         list_add_tail(&transport->node, &ltt_transport_list);
 247         mutex_unlock(&sessions_mutex);
 248 }
 249 EXPORT_SYMBOL_GPL(ltt_transport_register);
 250
 251 /**
 252  * ltt_transport_unregister - LTT transport unregistration
 253  * @transport: transport structure
 254  */
 255 void ltt_transport_unregister(struct ltt_transport *transport)
 256 {
 257         mutex_lock(&sessions_mutex);
 258         list_del(&transport->node);
 259         mutex_unlock(&sessions_mutex);
 260 }
 261 EXPORT_SYMBOL_GPL(ltt_transport_unregister);
 262
 263
 264 static int __init ltt_events_init(void)
 265 {
 266         int ret;
 267
 268         event_cache = KMEM_CACHE(ltt_event, 0);
 269         if (!event_cache)
 270                 return -ENOMEM;
 271         ret = ltt_debugfs_abi_init();
 272         if (ret)
 273                 goto error;
 274         return 0;
 275 error:
 276         kmem_cache_destroy(event_cache);
 277         return ret;
 278 }
 279
 280 module_init(ltt_events_init);
 281
 282 static void __exit ltt_events_exit(void)
 283 {
 284         struct ltt_session *session, *tmpsession;
 285
 286         ltt_debugfs_abi_exit();
 287         list_for_each_entry_safe(session, tmpsession, &sessions, list)
 288                 ltt_session_destroy(session);
 289         kmem_cache_destroy(event_cache);
 290 }
 291
 292 module_exit(ltt_events_exit);
 293
 294 MODULE_LICENSE("GPL and additional rights");
 295 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 296 MODULE_DESCRIPTION("LTTng Events");