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