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