libust/channels.c

   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  * This library is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU Lesser General Public
  13  * License as published by the Free Software Foundation; either
  14  * version 2.1 of the License, or (at your option) any later version.
  15  *
  16  * This library is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19  * Lesser General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU Lesser General Public
  22  * License along with this library; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
  24  */
  25
  26 #include <stdlib.h>
  27 #include <ust/marker.h>
  28 #include "channels.h"
  29 #include "usterr_signal_safe.h"
  30
  31 /*
  32  * ltt_channel_mutex may be nested inside the LTT trace mutex.
  33  * ltt_channel_mutex mutex may be nested inside markers mutex.
  34  */
  35 static DEFINE_MUTEX(ltt_channel_mutex);
  36 static CDS_LIST_HEAD(ltt_channels);
  37 /*
  38  * Index of next channel in array. Makes sure that as long as a trace channel is
  39  * allocated, no array index will be re-used when a channel is freed and then
  40  * another channel is allocated. This index is cleared and the array indexeds
  41  * get reassigned when the index_urcu_ref goes back to 0, which indicates that no
  42  * more trace channels are allocated.
  43  */
  44 static unsigned int free_index;
  45 static struct urcu_ref index_urcu_ref;  /* Keeps track of allocated trace channels */
  46
  47 int ust_channels_overwrite_by_default = 0;
  48 int ust_channels_request_collection_by_default = 1;
  49
  50 static struct ltt_channel_setting *lookup_channel(const char *name)
  51 {
  52         struct ltt_channel_setting *iter;
  53
  54         cds_list_for_each_entry(iter, &ltt_channels, list)
  55                 if (strcmp(name, iter->name) == 0)
  56                         return iter;
  57         return NULL;
  58 }
  59
  60 /*
  61  * Must be called when channel refcount falls to 0 _and_ also when the last
  62  * trace is freed. This function is responsible for compacting the channel and
  63  * event IDs when no users are active.
  64  *
  65  * Called with lock_markers() and channels mutex held.
  66  */
  67 static void release_channel_setting(struct urcu_ref *urcu_ref)
  68 {
  69         struct ltt_channel_setting *setting = _ust_container_of(urcu_ref,
  70                 struct ltt_channel_setting, urcu_ref);
  71         struct ltt_channel_setting *iter;
  72
  73         if (uatomic_read(&index_urcu_ref.refcount) == 0
  74             && uatomic_read(&setting->urcu_ref.refcount) == 0) {
  75                 cds_list_del(&setting->list);
  76                 free(setting);
  77
  78                 free_index = 0;
  79                 cds_list_for_each_entry(iter, &ltt_channels, list) {
  80                         iter->index = free_index++;
  81                         iter->free_event_id = 0;
  82                 }
  83                 /* FIXME: why not run this? */
  84 //ust//         markers_compact_event_ids();
  85         }
  86 }
  87
  88 /*
  89  * Perform channel index compaction when the last trace channel is freed.
  90  *
  91  * Called with lock_markers() and channels mutex held.
  92  */
  93 static void release_trace_channel(struct urcu_ref *urcu_ref)
  94 {
  95         struct ltt_channel_setting *iter, *n;
  96
  97         cds_list_for_each_entry_safe(iter, n, &ltt_channels, list)
  98                 release_channel_setting(&iter->urcu_ref);
  99 }
 100
 101 /**
 102  * ltt_channels_register - Register a trace channel.
 103  * @name: channel name
 104  *
 105  * Uses refcounting.
 106  */
 107 int ltt_channels_register(const char *name)
 108 {
 109         struct ltt_channel_setting *setting;
 110         int ret = 0;
 111
 112         pthread_mutex_lock(&ltt_channel_mutex);
 113         setting = lookup_channel(name);
 114         if (setting) {
 115                 if (uatomic_read(&setting->urcu_ref.refcount) == 0)
 116                         goto init_urcu_ref;
 117                 else {
 118                         urcu_ref_get(&setting->urcu_ref);
 119                         goto end;
 120                 }
 121         }
 122         setting = zmalloc(sizeof(*setting));
 123         if (!setting) {
 124                 ret = -ENOMEM;
 125                 goto end;
 126         }
 127         cds_list_add(&setting->list, &ltt_channels);
 128         strncpy(setting->name, name, PATH_MAX-1);
 129         setting->index = free_index++;
 130 init_urcu_ref:
 131         urcu_ref_init(&setting->urcu_ref);
 132 end:
 133         pthread_mutex_unlock(&ltt_channel_mutex);
 134         return ret;
 135 }
 136 //ust// EXPORT_SYMBOL_GPL(ltt_channels_register);
 137
 138 /**
 139  * ltt_channels_unregister - Unregister a trace channel.
 140  * @name: channel name
 141  *
 142  * Must be called with markers mutex held.
 143  */
 144 int ltt_channels_unregister(const char *name)
 145 {
 146         struct ltt_channel_setting *setting;
 147         int ret = 0;
 148
 149         pthread_mutex_lock(&ltt_channel_mutex);
 150         setting = lookup_channel(name);
 151         if (!setting || uatomic_read(&setting->urcu_ref.refcount) == 0) {
 152                 ret = -ENOENT;
 153                 goto end;
 154         }
 155         urcu_ref_put(&setting->urcu_ref, release_channel_setting);
 156 end:
 157         pthread_mutex_unlock(&ltt_channel_mutex);
 158         return ret;
 159 }
 160 //ust// EXPORT_SYMBOL_GPL(ltt_channels_unregister);
 161
 162 /**
 163  * ltt_channels_set_default - Set channel default behavior.
 164  * @name: default channel name
 165  * @subbuf_size: size of the subbuffers
 166  * @subbuf_cnt: number of subbuffers
 167  */
 168 int ltt_channels_set_default(const char *name,
 169                              unsigned int subbuf_size,
 170                              unsigned int subbuf_cnt)
 171 {
 172         struct ltt_channel_setting *setting;
 173         int ret = 0;
 174
 175         pthread_mutex_lock(&ltt_channel_mutex);
 176         setting = lookup_channel(name);
 177         if (!setting || uatomic_read(&setting->urcu_ref.refcount) == 0) {
 178                 ret = -ENOENT;
 179                 goto end;
 180         }
 181         setting->subbuf_size = subbuf_size;
 182         setting->subbuf_cnt = subbuf_cnt;
 183 end:
 184         pthread_mutex_unlock(&ltt_channel_mutex);
 185         return ret;
 186 }
 187 //ust// EXPORT_SYMBOL_GPL(ltt_channels_set_default);
 188
 189 /**
 190  * ltt_channels_get_name_from_index - get channel name from channel index
 191  * @index: channel index
 192  *
 193  * Allows to lookup the channel name given its index. Done to keep the name
 194  * information outside of each trace channel instance.
 195  */
 196 const char *ltt_channels_get_name_from_index(unsigned int index)
 197 {
 198         struct ltt_channel_setting *iter;
 199
 200         cds_list_for_each_entry(iter, &ltt_channels, list)
 201                 if (iter->index == index && uatomic_read(&iter->urcu_ref.refcount))
 202                         return iter->name;
 203         return NULL;
 204 }
 205 //ust// EXPORT_SYMBOL_GPL(ltt_channels_get_name_from_index);
 206
 207 static struct ltt_channel_setting *
 208 ltt_channels_get_setting_from_name(const char *name)
 209 {
 210         struct ltt_channel_setting *iter;
 211
 212         cds_list_for_each_entry(iter, &ltt_channels, list)
 213                 if (!strcmp(iter->name, name)
 214                     && uatomic_read(&iter->urcu_ref.refcount))
 215                         return iter;
 216         return NULL;
 217 }
 218
 219 /**
 220  * ltt_channels_get_index_from_name - get channel index from channel name
 221  * @name: channel name
 222  *
 223  * Allows to lookup the channel index given its name. Done to keep the name
 224  * information outside of each trace channel instance.
 225  * Returns -1 if not found.
 226  */
 227 int ltt_channels_get_index_from_name(const char *name)
 228 {
 229         struct ltt_channel_setting *setting;
 230
 231         setting = ltt_channels_get_setting_from_name(name);
 232         if (setting)
 233                 return setting->index;
 234         else
 235                 return -1;
 236 }
 237 //ust// EXPORT_SYMBOL_GPL(ltt_channels_get_index_from_name);
 238
 239 /**
 240  * ltt_channels_trace_alloc - Allocate channel structures for a trace
 241  * @subbuf_size: subbuffer size. 0 uses default.
 242  * @subbuf_cnt: number of subbuffers per per-cpu buffers. 0 uses default.
 243  * @flags: Default channel flags
 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 struct ust_channel *ltt_channels_trace_alloc(unsigned int *nr_channels,
 250                                                     int overwrite,
 251                                                     int request_collection,
 252                                                     int active)
 253 {
 254         struct ust_channel *channel = NULL;
 255         struct ltt_channel_setting *iter;
 256
 257         pthread_mutex_lock(&ltt_channel_mutex);
 258         if (!free_index) {
 259                 WARN("ltt_channels_trace_alloc: no free_index; are there any probes connected?");
 260                 goto end;
 261         }
 262         if (!uatomic_read(&index_urcu_ref.refcount))
 263                 urcu_ref_init(&index_urcu_ref);
 264         else
 265                 urcu_ref_get(&index_urcu_ref);
 266         *nr_channels = free_index;
 267         channel = zmalloc(sizeof(struct ust_channel) * free_index);
 268         if (!channel) {
 269                 WARN("ltt_channel_struct: channel null after alloc");
 270                 goto end;
 271         }
 272         cds_list_for_each_entry(iter, &ltt_channels, list) {
 273                 if (!uatomic_read(&iter->urcu_ref.refcount))
 274                         continue;
 275                 channel[iter->index].subbuf_size = iter->subbuf_size;
 276                 channel[iter->index].subbuf_cnt = iter->subbuf_cnt;
 277                 channel[iter->index].overwrite = overwrite;
 278                 channel[iter->index].request_collection = request_collection;
 279                 channel[iter->index].active = active;
 280                 channel[iter->index].channel_name = iter->name;
 281         }
 282 end:
 283         pthread_mutex_unlock(&ltt_channel_mutex);
 284         return channel;
 285 }
 286 //ust// EXPORT_SYMBOL_GPL(ltt_channels_trace_alloc);
 287
 288 /**
 289  * ltt_channels_trace_free - Free one trace's channels
 290  * @channels: channels to free
 291  *
 292  * Called with trace lock held. The actual channel buffers must be freed before
 293  * this function is called.
 294  */
 295 void ltt_channels_trace_free(struct ust_channel *channels)
 296 {
 297         lock_ust_marker();
 298         pthread_mutex_lock(&ltt_channel_mutex);
 299         free(channels);
 300         urcu_ref_put(&index_urcu_ref, release_trace_channel);
 301         pthread_mutex_unlock(&ltt_channel_mutex);
 302         unlock_ust_marker();
 303 }
 304 //ust// EXPORT_SYMBOL_GPL(ltt_channels_trace_free);
 305
 306 /**
 307  * _ltt_channels_get_event_id - get next event ID for a marker
 308  * @channel: channel name
 309  * @name: event name
 310  *
 311  * Returns a unique event ID (for this channel) or < 0 on error.
 312  * Must be called with channels mutex held.
 313  */
 314 int _ltt_channels_get_event_id(const char *channel, const char *name)
 315 {
 316         struct ltt_channel_setting *setting;
 317         int ret;
 318
 319         setting = ltt_channels_get_setting_from_name(channel);
 320         if (!setting) {
 321                 ret = -ENOENT;
 322                 goto end;
 323         }
 324         if (strcmp(channel, "metadata") == 0) {
 325                 if (strcmp(name, "core_marker_id") == 0)
 326                         ret = 0;
 327                 else if (strcmp(name, "core_marker_format") == 0)
 328                         ret = 1;
 329                 else if (strcmp(name, "testev") == 0)
 330                         ret = 2;
 331                 else
 332                         ret = -ENOENT;
 333                 goto end;
 334         }
 335         if (setting->free_event_id == EVENTS_PER_CHANNEL - 1) {
 336                 ret = -ENOSPC;
 337                 goto end;
 338         }
 339         ret = setting->free_event_id++;
 340 end:
 341         return ret;
 342 }
 343
 344 /**
 345  * ltt_channels_get_event_id - get next event ID for a marker
 346  * @channel: channel name
 347  * @name: event name
 348  *
 349  * Returns a unique event ID (for this channel) or < 0 on error.
 350  */
 351 int ltt_channels_get_event_id(const char *channel, const char *name)
 352 {
 353         int ret;
 354
 355         pthread_mutex_lock(&ltt_channel_mutex);
 356         ret = _ltt_channels_get_event_id(channel, name);
 357         pthread_mutex_unlock(&ltt_channel_mutex);
 358         return ret;
 359 }
 360
 361 //ust// MODULE_LICENSE("GPL");
 362 //ust// MODULE_AUTHOR("Mathieu Desnoyers");
 363 //ust// MODULE_DESCRIPTION("Linux Trace Toolkit Next Generation Channel Management");