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 = kzalloc(sizeof(struct ltt_session), GFP_KERNEL);
  36         if (!session)
  37                 return NULL;
  38         INIT_LIST_HEAD(&session->chan);
  39         INIT_LIST_HEAD(&session->events);
  40         list_add(&session->list, &sessions);
  41         mutex_unlock(&sessions_mutex);
  42         return session;
  43 }
  44
  45 void ltt_session_destroy(struct ltt_session *session)
  46 {
  47         struct ltt_channel *chan, *tmpchan;
  48         struct ltt_event *event, *tmpevent;
  49         int ret;
  50
  51         mutex_lock(&sessions_mutex);
  52         ACCESS_ONCE(session->active) = 0;
  53         list_for_each_entry(event, &session->events, list) {
  54                 ret = _ltt_event_unregister(event);
  55                 WARN_ON(ret);
  56         }
  57         synchronize_trace();    /* Wait for in-flight events to complete */
  58         list_for_each_entry_safe(event, tmpevent, &session->events, list)
  59                 _ltt_event_destroy(event);
  60         list_for_each_entry_safe(chan, tmpchan, &session->chan, list)
  61                 _ltt_channel_destroy(chan);
  62         list_del(&session->list);
  63         mutex_unlock(&sessions_mutex);
  64         kfree(session);
  65 }
  66
  67 int ltt_session_start(struct ltt_session *session)
  68 {
  69         int ret = 0;
  70
  71         mutex_lock(&sessions_mutex);
  72         if (session->active) {
  73                 ret = -EBUSY;
  74                 goto end;
  75         }
  76         ACCESS_ONCE(session->active) = 1;
  77         synchronize_trace();    /* Wait for in-flight events to complete */
  78 end:
  79         mutex_unlock(&sessions_mutex);
  80         return ret;
  81 }
  82
  83 int ltt_session_stop(struct ltt_session *session)
  84 {
  85         int ret = 0;
  86
  87         mutex_lock(&sessions_mutex);
  88         if (!session->active) {
  89                 ret = -EBUSY;
  90                 goto end;
  91         }
  92         ACCESS_ONCE(session->active) = 0;
  93         synchronize_trace();    /* Wait for in-flight events to complete */
  94 end:
  95         mutex_unlock(&sessions_mutex);
  96         return ret;
  97 }
  98
  99 static struct ltt_transport *ltt_transport_find(char *name)
 100 {
 101         struct ltt_transport *transport;
 102
 103         list_for_each_entry(transport, &ltt_transport_list, node) {
 104                 if (!strcmp(transport->name, name))
 105                         return transport;
 106         }
 107         return NULL;
 108 }
 109
 110 struct ltt_channel *ltt_channel_create(struct ltt_session *session,
 111                                        int overwrite, void *buf_addr,
 112                                        size_t subbuf_size, size_t num_subbuf,
 113                                        unsigned int switch_timer_interval,
 114                                        unsigned int read_timer_interval)
 115 {
 116         struct ltt_channel *chan;
 117         struct ltt_transport *transport;
 118         char *transport_name;
 119
 120         mutex_lock(&sessions_mutex);
 121         if (session->active) {
 122                 printk(KERN_WARNING "LTTng refusing to add channel to active session\n");
 123                 goto active;    /* Refuse to add channel to active session */
 124         }
 125         transport_name = overwrite ? "relay-overwrite" : "relay-discard";
 126         transport = ltt_transport_find(transport_name);
 127         if (!transport) {
 128                 printk(KERN_WARNING "LTTng transport %s not found\n",
 129                        transport_name);
 130                 goto notransport;
 131         }
 132         chan = kzalloc(sizeof(struct ltt_channel), GFP_KERNEL);
 133         if (!chan)
 134                 goto nomem;
 135         chan->session = session;
 136         init_waitqueue_head(&chan->notify_wait);
 137         chan->chan = transport->ops.channel_create("[lttng]", session, buf_addr,
 138                         subbuf_size, num_subbuf, switch_timer_interval,
 139                         read_timer_interval);
 140         if (!chan->chan)
 141                 goto create_error;
 142         chan->ops = &transport->ops;
 143         list_add(&chan->list, &session->chan);
 144         mutex_unlock(&sessions_mutex);
 145         return chan;
 146
 147 create_error:
 148         kfree(chan);
 149 nomem:
 150 notransport:
 151 active:
 152         mutex_unlock(&sessions_mutex);
 153         return NULL;
 154 }
 155
 156 /*
 157  * Only used internally at session destruction.
 158  */
 159 void _ltt_channel_destroy(struct ltt_channel *chan)
 160 {
 161         chan->ops->channel_destroy(chan->chan);
 162         list_del(&chan->list);
 163         kfree(chan);
 164 }
 165
 166 /*
 167  * Supports event creation while tracing session is active.
 168  */
 169 struct ltt_event *ltt_event_create(struct ltt_channel *chan, char *name,
 170                                    enum instrum_type itype,
 171                                    void *probe, void *filter)
 172 {
 173         struct ltt_event *event;
 174         int ret;
 175
 176         mutex_lock(&sessions_mutex);
 177         if (chan->free_event_id == -1UL)
 178                 goto full;
 179         /*
 180          * This is O(n^2) (for each event, the loop is called at event
 181          * creation). Might require a hash if we have lots of events.
 182          */
 183         list_for_each_entry(event, &chan->session->events, list)
 184                 if (!strcmp(event->name, name))
 185                         goto exist;
 186         event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
 187         if (!event)
 188                 goto cache_error;
 189         event->name = kmalloc(strlen(name) + 1, GFP_KERNEL);
 190         if (!event->name)
 191                 goto name_error;
 192         strcpy(event->name, name);
 193         event->chan = chan;
 194         event->probe = probe;
 195         event->filter = filter;
 196         event->id = chan->free_event_id++;
 197         event->itype = itype;
 198         /* Populate ltt_event structure before tracepoint registration. */
 199         smp_wmb();
 200         switch (itype) {
 201         case INSTRUM_TRACEPOINTS:
 202                 ret = tracepoint_probe_register(name, probe, event);
 203                 if (ret)
 204                         goto register_error;
 205                 break;
 206         default:
 207                 WARN_ON_ONCE(1);
 208         }
 209         list_add(&event->list, &chan->session->events);
 210         mutex_unlock(&sessions_mutex);
 211         return event;
 212
 213 register_error:
 214         kfree(event->name);
 215 name_error:
 216         kmem_cache_free(event_cache, event);
 217 cache_error:
 218 exist:
 219 full:
 220         mutex_unlock(&sessions_mutex);
 221         return NULL;
 222 }
 223
 224 /*
 225  * Only used internally at session destruction.
 226  */
 227 int _ltt_event_unregister(struct ltt_event *event)
 228 {
 229         int ret = -EINVAL;
 230
 231         switch (event->itype) {
 232         case INSTRUM_TRACEPOINTS:
 233                 ret = tracepoint_probe_unregister(event->name, event->probe,
 234                                                   event);
 235                 if (ret)
 236                         return ret;
 237                 break;
 238         default:
 239                 WARN_ON_ONCE(1);
 240         }
 241         return ret;
 242 }
 243
 244 /*
 245  * Only used internally at session destruction.
 246  */
 247 void _ltt_event_destroy(struct ltt_event *event)
 248 {
 249         kfree(event->name);
 250         list_del(&event->list);
 251         kmem_cache_free(event_cache, event);
 252 }
 253
 254 /**
 255  * ltt_transport_register - LTT transport registration
 256  * @transport: transport structure
 257  *
 258  * Registers a transport which can be used as output to extract the data out of
 259  * LTTng. The module calling this registration function must ensure that no
 260  * trap-inducing code will be executed by the transport functions. E.g.
 261  * vmalloc_sync_all() must be called between a vmalloc and the moment the memory
 262  * is made visible to the transport function. This registration acts as a
 263  * vmalloc_sync_all. Therefore, only if the module allocates virtual memory
 264  * after its registration must it synchronize the TLBs.
 265  */
 266 void ltt_transport_register(struct ltt_transport *transport)
 267 {
 268         /*
 269          * Make sure no page fault can be triggered by the module about to be
 270          * registered. We deal with this here so we don't have to call
 271          * vmalloc_sync_all() in each module's init.
 272          */
 273         vmalloc_sync_all();
 274
 275         mutex_lock(&sessions_mutex);
 276         list_add_tail(&transport->node, &ltt_transport_list);
 277         mutex_unlock(&sessions_mutex);
 278 }
 279 EXPORT_SYMBOL_GPL(ltt_transport_register);
 280
 281 /**
 282  * ltt_transport_unregister - LTT transport unregistration
 283  * @transport: transport structure
 284  */
 285 void ltt_transport_unregister(struct ltt_transport *transport)
 286 {
 287         mutex_lock(&sessions_mutex);
 288         list_del(&transport->node);
 289         mutex_unlock(&sessions_mutex);
 290 }
 291 EXPORT_SYMBOL_GPL(ltt_transport_unregister);
 292
 293
 294 static int __init ltt_events_init(void)
 295 {
 296         int ret;
 297
 298         event_cache = KMEM_CACHE(ltt_event, 0);
 299         if (!event_cache)
 300                 return -ENOMEM;
 301         ret = ltt_probes_init();
 302         if (ret)
 303                 goto error;
 304         ret = ltt_debugfs_abi_init();
 305         if (ret)
 306                 goto error_abi;
 307         return 0;
 308 error_abi:
 309         ltt_probes_exit();
 310 error:
 311         kmem_cache_destroy(event_cache);
 312         return ret;
 313 }
 314
 315 module_init(ltt_events_init);
 316
 317 static void __exit ltt_events_exit(void)
 318 {
 319         struct ltt_session *session, *tmpsession;
 320
 321         ltt_debugfs_abi_exit();
 322         ltt_probes_exit();
 323         list_for_each_entry_safe(session, tmpsession, &sessions, list)
 324                 ltt_session_destroy(session);
 325         kmem_cache_destroy(event_cache);
 326 }
 327
 328 module_exit(ltt_events_exit);
 329
 330 MODULE_LICENSE("GPL and additional rights");
 331 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 332 MODULE_DESCRIPTION("LTTng Events");