| 1 | /* |
| 2 | * ltt/ltt-channels.c |
| 3 | * |
| 4 | * (C) Copyright 2008 - Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca) |
| 5 | * |
| 6 | * LTTng channel management. |
| 7 | * |
| 8 | * Author: |
| 9 | * Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca) |
| 10 | * |
| 11 | * Dual LGPL v2.1/GPL v2 license. |
| 12 | */ |
| 13 | |
| 14 | #include <linux/module.h> |
| 15 | #include <linux/mutex.h> |
| 16 | #include <linux/slab.h> |
| 17 | #include <linux/vmalloc.h> |
| 18 | #include "ltt-channels.h" |
| 19 | |
| 20 | /* |
| 21 | * ltt_channel_mutex may be nested inside the LTT trace mutex. |
| 22 | * ltt_channel_mutex mutex may be nested inside markers mutex. |
| 23 | */ |
| 24 | static DEFINE_MUTEX(ltt_channel_mutex); |
| 25 | static LIST_HEAD(ltt_channels); |
| 26 | /* |
| 27 | * Index of next channel in array. Makes sure that as long as a trace channel is |
| 28 | * allocated, no array index will be re-used when a channel is freed and then |
| 29 | * another channel is allocated. This index is cleared and the array indexeds |
| 30 | * get reassigned when the index_kref goes back to 0, which indicates that no |
| 31 | * more trace channels are allocated. |
| 32 | */ |
| 33 | static unsigned int free_index; |
| 34 | /* index_kref is protected by both ltt_channel_mutex and lock_markers */ |
| 35 | static struct kref index_kref; /* Keeps track of allocated trace channels */ |
| 36 | |
| 37 | static struct ltt_channel_setting *lookup_channel(const char *name) |
| 38 | { |
| 39 | struct ltt_channel_setting *iter; |
| 40 | |
| 41 | list_for_each_entry(iter, <t_channels, list) |
| 42 | if (strcmp(name, iter->name) == 0) |
| 43 | return iter; |
| 44 | return NULL; |
| 45 | } |
| 46 | |
| 47 | /* |
| 48 | * Must be called when channel refcount falls to 0 _and_ also when the last |
| 49 | * trace is freed. This function is responsible for compacting the channel and |
| 50 | * event IDs when no users are active. |
| 51 | * |
| 52 | * Called with lock_markers() and channels mutex held. |
| 53 | */ |
| 54 | static void release_channel_setting(struct kref *kref) |
| 55 | { |
| 56 | struct ltt_channel_setting *setting = container_of(kref, |
| 57 | struct ltt_channel_setting, kref); |
| 58 | struct ltt_channel_setting *iter; |
| 59 | |
| 60 | if (atomic_read(&index_kref.refcount) == 0 |
| 61 | && atomic_read(&setting->kref.refcount) == 0) { |
| 62 | list_del(&setting->list); |
| 63 | kfree(setting); |
| 64 | |
| 65 | free_index = 0; |
| 66 | list_for_each_entry(iter, <t_channels, list) { |
| 67 | iter->index = free_index++; |
| 68 | iter->free_event_id = 0; |
| 69 | } |
| 70 | } |
| 71 | } |
| 72 | |
| 73 | /* |
| 74 | * Perform channel index compaction when the last trace channel is freed. |
| 75 | * |
| 76 | * Called with lock_markers() and channels mutex held. |
| 77 | */ |
| 78 | static void release_trace_channel(struct kref *kref) |
| 79 | { |
| 80 | struct ltt_channel_setting *iter, *n; |
| 81 | |
| 82 | list_for_each_entry_safe(iter, n, <t_channels, list) |
| 83 | release_channel_setting(&iter->kref); |
| 84 | if (atomic_read(&index_kref.refcount) == 0) |
| 85 | markers_compact_event_ids(); |
| 86 | } |
| 87 | |
| 88 | /* |
| 89 | * ltt_channel_trace_ref : Is there an existing trace session ? |
| 90 | * |
| 91 | * Must be called with lock_markers() held. |
| 92 | */ |
| 93 | int ltt_channels_trace_ref(void) |
| 94 | { |
| 95 | return !!atomic_read(&index_kref.refcount); |
| 96 | } |
| 97 | EXPORT_SYMBOL_GPL(ltt_channels_trace_ref); |
| 98 | |
| 99 | /** |
| 100 | * ltt_channels_register - Register a trace channel. |
| 101 | * @name: channel name |
| 102 | * |
| 103 | * Uses refcounting. |
| 104 | */ |
| 105 | int ltt_channels_register(const char *name) |
| 106 | { |
| 107 | struct ltt_channel_setting *setting; |
| 108 | int ret = 0; |
| 109 | |
| 110 | mutex_lock(<t_channel_mutex); |
| 111 | setting = lookup_channel(name); |
| 112 | if (setting) { |
| 113 | if (atomic_read(&setting->kref.refcount) == 0) |
| 114 | goto init_kref; |
| 115 | else { |
| 116 | kref_get(&setting->kref); |
| 117 | goto end; |
| 118 | } |
| 119 | } |
| 120 | setting = kzalloc(sizeof(*setting), GFP_KERNEL); |
| 121 | if (!setting) { |
| 122 | ret = -ENOMEM; |
| 123 | goto end; |
| 124 | } |
| 125 | list_add(&setting->list, <t_channels); |
| 126 | strncpy(setting->name, name, PATH_MAX-1); |
| 127 | setting->index = free_index++; |
| 128 | init_kref: |
| 129 | kref_init(&setting->kref); |
| 130 | end: |
| 131 | mutex_unlock(<t_channel_mutex); |
| 132 | return ret; |
| 133 | } |
| 134 | EXPORT_SYMBOL_GPL(ltt_channels_register); |
| 135 | |
| 136 | /** |
| 137 | * ltt_channels_unregister - Unregister a trace channel. |
| 138 | * @name: channel name |
| 139 | * @compacting: performing compaction |
| 140 | * |
| 141 | * Must be called with markers mutex held. |
| 142 | */ |
| 143 | int ltt_channels_unregister(const char *name, int compacting) |
| 144 | { |
| 145 | struct ltt_channel_setting *setting; |
| 146 | int ret = 0; |
| 147 | |
| 148 | if (!compacting) |
| 149 | mutex_lock(<t_channel_mutex); |
| 150 | setting = lookup_channel(name); |
| 151 | if (!setting || atomic_read(&setting->kref.refcount) == 0) { |
| 152 | ret = -ENOENT; |
| 153 | goto end; |
| 154 | } |
| 155 | kref_put(&setting->kref, release_channel_setting); |
| 156 | if (!compacting && atomic_read(&index_kref.refcount) == 0) |
| 157 | markers_compact_event_ids(); |
| 158 | end: |
| 159 | if (!compacting) |
| 160 | mutex_unlock(<t_channel_mutex); |
| 161 | return ret; |
| 162 | } |
| 163 | EXPORT_SYMBOL_GPL(ltt_channels_unregister); |
| 164 | |
| 165 | /** |
| 166 | * ltt_channels_set_default - Set channel default behavior. |
| 167 | * @name: default channel name |
| 168 | * @sb_size: size of the subbuffers |
| 169 | * @n_sb: number of subbuffers |
| 170 | */ |
| 171 | int ltt_channels_set_default(const char *name, |
| 172 | unsigned int sb_size, |
| 173 | unsigned int n_sb) |
| 174 | { |
| 175 | struct ltt_channel_setting *setting; |
| 176 | int ret = 0; |
| 177 | |
| 178 | mutex_lock(<t_channel_mutex); |
| 179 | setting = lookup_channel(name); |
| 180 | if (!setting || atomic_read(&setting->kref.refcount) == 0) { |
| 181 | ret = -ENOENT; |
| 182 | goto end; |
| 183 | } |
| 184 | setting->sb_size = sb_size; |
| 185 | setting->n_sb = n_sb; |
| 186 | end: |
| 187 | mutex_unlock(<t_channel_mutex); |
| 188 | return ret; |
| 189 | } |
| 190 | EXPORT_SYMBOL_GPL(ltt_channels_set_default); |
| 191 | |
| 192 | /** |
| 193 | * ltt_channels_get_name_from_index - get channel name from channel index |
| 194 | * @index: channel index |
| 195 | * |
| 196 | * Allows to lookup the channel name given its index. Done to keep the name |
| 197 | * information outside of each trace channel instance. |
| 198 | */ |
| 199 | const char *ltt_channels_get_name_from_index(unsigned int index) |
| 200 | { |
| 201 | struct ltt_channel_setting *iter; |
| 202 | |
| 203 | list_for_each_entry(iter, <t_channels, list) |
| 204 | if (iter->index == index && atomic_read(&iter->kref.refcount)) |
| 205 | return iter->name; |
| 206 | return NULL; |
| 207 | } |
| 208 | EXPORT_SYMBOL_GPL(ltt_channels_get_name_from_index); |
| 209 | |
| 210 | static struct ltt_channel_setting * |
| 211 | ltt_channels_get_setting_from_name(const char *name) |
| 212 | { |
| 213 | struct ltt_channel_setting *iter; |
| 214 | |
| 215 | list_for_each_entry(iter, <t_channels, list) |
| 216 | if (!strcmp(iter->name, name) |
| 217 | && atomic_read(&iter->kref.refcount)) |
| 218 | return iter; |
| 219 | return NULL; |
| 220 | } |
| 221 | |
| 222 | /** |
| 223 | * ltt_channels_get_index_from_name - get channel index from channel name |
| 224 | * @name: channel name |
| 225 | * |
| 226 | * Allows to lookup the channel index given its name. Done to keep the name |
| 227 | * information outside of each trace channel instance. |
| 228 | * Returns -1 if not found. |
| 229 | */ |
| 230 | int ltt_channels_get_index_from_name(const char *name) |
| 231 | { |
| 232 | struct ltt_channel_setting *setting; |
| 233 | |
| 234 | setting = ltt_channels_get_setting_from_name(name); |
| 235 | if (setting) |
| 236 | return setting->index; |
| 237 | else |
| 238 | return -1; |
| 239 | } |
| 240 | EXPORT_SYMBOL_GPL(ltt_channels_get_index_from_name); |
| 241 | |
| 242 | /** |
| 243 | * ltt_channels_trace_alloc - Allocate channel structures for a trace |
| 244 | * |
| 245 | * Use the current channel list to allocate the channels for a trace. |
| 246 | * Called with trace lock held. Does not perform the trace buffer allocation, |
| 247 | * because we must let the user overwrite specific channel sizes. |
| 248 | */ |
| 249 | int ltt_channels_trace_alloc(struct ltt_trace *trace, int overwrite) |
| 250 | { |
| 251 | struct channel **chan = NULL; |
| 252 | struct ltt_channel_setting *chans, *iter; |
| 253 | int ret = 0; |
| 254 | |
| 255 | lock_markers(); |
| 256 | mutex_lock(<t_channel_mutex); |
| 257 | if (!free_index) |
| 258 | goto end; |
| 259 | if (!atomic_read(&index_kref.refcount)) |
| 260 | kref_init(&index_kref); |
| 261 | else |
| 262 | kref_get(&index_kref); |
| 263 | trace->nr_channels = free_index; |
| 264 | chan = kzalloc(sizeof(struct channel *) * free_index, GFP_KERNEL); |
| 265 | if (!chan) |
| 266 | goto end; |
| 267 | chans = kzalloc(sizeof(struct ltt_channel_setting) * free_index, |
| 268 | GFP_KERNEL); |
| 269 | if (!chan_settings) |
| 270 | goto free_chan; |
| 271 | list_for_each_entry(iter, <t_channels, list) { |
| 272 | if (!atomic_read(&iter->kref.refcount)) |
| 273 | continue; |
| 274 | chans[iter->index].sb_size = iter->sb_size; |
| 275 | chans[iter->index].n_sb = iter->n_sb; |
| 276 | chans[iter->index].overwrite = overwrite; |
| 277 | strncpy(chans[iter->index].filename, iter->name, |
| 278 | NAME_MAX - 1); |
| 279 | chans[iter->index].switch_timer_interval = 0; |
| 280 | chans[iter->index].read_timer_interval = LTT_READ_TIMER_INTERVAL; |
| 281 | } |
| 282 | trace->channels = chan; |
| 283 | trace->settings = chans; |
| 284 | end: |
| 285 | mutex_unlock(<t_channel_mutex); |
| 286 | unlock_markers(); |
| 287 | return ret; |
| 288 | |
| 289 | free_chan: |
| 290 | kfree(chan); |
| 291 | ret = -ENOMEM; |
| 292 | goto end; |
| 293 | } |
| 294 | EXPORT_SYMBOL_GPL(ltt_channels_trace_alloc); |
| 295 | |
| 296 | /** |
| 297 | * ltt_channels_trace_free - Free one trace's channels |
| 298 | * @channels: channels to free |
| 299 | * |
| 300 | * Called with trace lock held. The actual channel buffers must be freed before |
| 301 | * this function is called. |
| 302 | */ |
| 303 | void ltt_channels_trace_free(struct ltt_trace *trace) |
| 304 | { |
| 305 | lock_markers(); |
| 306 | mutex_lock(<t_channel_mutex); |
| 307 | kfree(trace->settings); |
| 308 | kfree(trace->channels); |
| 309 | kref_put(&index_kref, release_trace_channel); |
| 310 | mutex_unlock(<t_channel_mutex); |
| 311 | unlock_markers(); |
| 312 | marker_update_probes(); |
| 313 | } |
| 314 | EXPORT_SYMBOL_GPL(ltt_channels_trace_free); |
| 315 | |
| 316 | /** |
| 317 | * ltt_channels_trace_set_timer - set switch timer |
| 318 | * @channel: channel |
| 319 | * @interval: interval of timer interrupt, in jiffies. 0 inhibits timer. |
| 320 | */ |
| 321 | |
| 322 | void ltt_channels_trace_set_timer(struct ltt_chan *chan, |
| 323 | unsigned long interval) |
| 324 | { |
| 325 | chan->switch_timer_interval = interval; |
| 326 | } |
| 327 | EXPORT_SYMBOL_GPL(ltt_channels_trace_set_timer); |
| 328 | |
| 329 | /** |
| 330 | * _ltt_channels_get_event_id - get next event ID for a marker |
| 331 | * @channel: channel name |
| 332 | * @name: event name |
| 333 | * |
| 334 | * Returns a unique event ID (for this channel) or < 0 on error. |
| 335 | * Must be called with channels mutex held. |
| 336 | */ |
| 337 | int _ltt_channels_get_event_id(const char *channel, const char *name) |
| 338 | { |
| 339 | struct ltt_channel_setting *setting; |
| 340 | int ret; |
| 341 | |
| 342 | setting = ltt_channels_get_setting_from_name(channel); |
| 343 | if (!setting) { |
| 344 | ret = -ENOENT; |
| 345 | goto end; |
| 346 | } |
| 347 | if (strcmp(channel, "metadata") == 0) { |
| 348 | if (strcmp(name, "core_marker_id") == 0) |
| 349 | ret = 0; |
| 350 | else if (strcmp(name, "core_marker_format") == 0) |
| 351 | ret = 1; |
| 352 | else |
| 353 | ret = -ENOENT; |
| 354 | goto end; |
| 355 | } |
| 356 | if (setting->free_event_id == EVENTS_PER_CHANNEL - 1) { |
| 357 | ret = -ENOSPC; |
| 358 | goto end; |
| 359 | } |
| 360 | ret = setting->free_event_id++; |
| 361 | end: |
| 362 | return ret; |
| 363 | } |
| 364 | |
| 365 | /** |
| 366 | * ltt_channels_get_event_id - get next event ID for a marker |
| 367 | * @channel: channel name |
| 368 | * @name: event name |
| 369 | * |
| 370 | * Returns a unique event ID (for this channel) or < 0 on error. |
| 371 | */ |
| 372 | int ltt_channels_get_event_id(const char *channel, const char *name) |
| 373 | { |
| 374 | int ret; |
| 375 | |
| 376 | mutex_lock(<t_channel_mutex); |
| 377 | ret = _ltt_channels_get_event_id(channel, name); |
| 378 | mutex_unlock(<t_channel_mutex); |
| 379 | return ret; |
| 380 | } |
| 381 | |
| 382 | /** |
| 383 | * ltt_channels_reset_event_ids - reset event IDs at compaction |
| 384 | * |
| 385 | * Called with lock marker and channel mutex held. |
| 386 | */ |
| 387 | void _ltt_channels_reset_event_ids(void) |
| 388 | { |
| 389 | struct ltt_channel_setting *iter; |
| 390 | |
| 391 | list_for_each_entry(iter, <t_channels, list) |
| 392 | iter->free_event_id = 0; |
| 393 | } |
| 394 | |
| 395 | MODULE_LICENSE("GPL and additional rights"); |
| 396 | MODULE_AUTHOR("Mathieu Desnoyers"); |
| 397 | MODULE_DESCRIPTION("Linux Trace Toolkit Next Generation Channel Management"); |