| 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, <t_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, <t_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 | event_cache = KMEM_CACHE(ltt_event, 0); |
| 267 | if (!event_cache) |
| 268 | return -ENOMEM; |
| 269 | return 0; |
| 270 | } |
| 271 | |
| 272 | module_init(ltt_events_init); |
| 273 | |
| 274 | static void __exit ltt_events_exit(void) |
| 275 | { |
| 276 | struct ltt_session *session, *tmpsession; |
| 277 | |
| 278 | list_for_each_entry_safe(session, tmpsession, &sessions, list) |
| 279 | ltt_session_destroy(session); |
| 280 | kmem_cache_destroy(event_cache); |
| 281 | } |
| 282 | |
| 283 | module_exit(ltt_events_exit); |
| 284 | |
| 285 | MODULE_LICENSE("GPL and additional rights"); |
| 286 | MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>"); |
| 287 | MODULE_DESCRIPTION("LTTng Events"); |