libtracing/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
  12 //ust// #include <linux/module.h>
  13 //ust// #include <linux/ltt-channels.h>
  14 //ust// #include <linux/mutex.h>
  15 //ust// #include <linux/vmalloc.h>
  16
  17 #include "kernelcompat.h"
  18 #include "channels.h"
  19 #include "usterr.h"
  20
  21 /*
  22  * ltt_channel_mutex may be nested inside the LTT trace mutex.
  23  * ltt_channel_mutex mutex may be nested inside markers mutex.
  24  */
  25 static DEFINE_MUTEX(ltt_channel_mutex);
  26 static LIST_HEAD(ltt_channels);
  27 /*
  28  * Index of next channel in array. Makes sure that as long as a trace channel is
  29  * allocated, no array index will be re-used when a channel is freed and then
  30  * another channel is allocated. This index is cleared and the array indexeds
  31  * get reassigned when the index_kref goes back to 0, which indicates that no
  32  * more trace channels are allocated.
  33  */
  34 static unsigned int free_index;
  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, &ltt_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, &ltt_channels, list) {
  67                         iter->index = free_index++;
  68                         iter->free_event_id = 0;
  69                 }
  70 //ust//         markers_compact_event_ids();
  71         }
  72 }
  73
  74 /*
  75  * Perform channel index compaction when the last trace channel is freed.
  76  *
  77  * Called with lock_markers() and channels mutex held.
  78  */
  79 static void release_trace_channel(struct kref *kref)
  80 {
  81         struct ltt_channel_setting *iter, *n;
  82
  83         list_for_each_entry_safe(iter, n, &ltt_channels, list)
  84                 release_channel_setting(&iter->kref);
  85 }
  86
  87 /**
  88  * ltt_channels_register - Register a trace channel.
  89  * @name: channel name
  90  *
  91  * Uses refcounting.
  92  */
  93 int ltt_channels_register(const char *name)
  94 {
  95         struct ltt_channel_setting *setting;
  96         int ret = 0;
  97
  98         mutex_lock(&ltt_channel_mutex);
  99         setting = lookup_channel(name);
 100         if (setting) {
 101                 if (atomic_read(&setting->kref.refcount) == 0)
 102                         goto init_kref;
 103                 else {
 104                         kref_get(&setting->kref);
 105                         goto end;
 106                 }
 107         }
 108         setting = kzalloc(sizeof(*setting), GFP_KERNEL);
 109         if (!setting) {
 110                 ret = -ENOMEM;
 111                 goto end;
 112         }
 113         list_add(&setting->list, &ltt_channels);
 114         strncpy(setting->name, name, PATH_MAX-1);
 115         setting->index = free_index++;
 116 init_kref:
 117         kref_init(&setting->kref);
 118 end:
 119         mutex_unlock(&ltt_channel_mutex);
 120         return ret;
 121 }
 122 //ust// EXPORT_SYMBOL_GPL(ltt_channels_register);
 123
 124 /**
 125  * ltt_channels_unregister - Unregister a trace channel.
 126  * @name: channel name
 127  *
 128  * Must be called with markers mutex held.
 129  */
 130 int ltt_channels_unregister(const char *name)
 131 {
 132         struct ltt_channel_setting *setting;
 133         int ret = 0;
 134
 135         mutex_lock(&ltt_channel_mutex);
 136         setting = lookup_channel(name);
 137         if (!setting || atomic_read(&setting->kref.refcount) == 0) {
 138                 ret = -ENOENT;
 139                 goto end;
 140         }
 141         kref_put(&setting->kref, release_channel_setting);
 142 end:
 143         mutex_unlock(&ltt_channel_mutex);
 144         return ret;
 145 }
 146 //ust// EXPORT_SYMBOL_GPL(ltt_channels_unregister);
 147
 148 /**
 149  * ltt_channels_set_default - Set channel default behavior.
 150  * @name: default channel name
 151  * @subbuf_size: size of the subbuffers
 152  * @subbuf_cnt: number of subbuffers
 153  */
 154 int ltt_channels_set_default(const char *name,
 155                              unsigned int subbuf_size,
 156                              unsigned int subbuf_cnt)
 157 {
 158         struct ltt_channel_setting *setting;
 159         int ret = 0;
 160
 161         mutex_lock(&ltt_channel_mutex);
 162         setting = lookup_channel(name);
 163         if (!setting || atomic_read(&setting->kref.refcount) == 0) {
 164                 ret = -ENOENT;
 165                 goto end;
 166         }
 167         setting->subbuf_size = subbuf_size;
 168         setting->subbuf_cnt = subbuf_cnt;
 169 end:
 170         mutex_unlock(&ltt_channel_mutex);
 171         return ret;
 172 }
 173 //ust// EXPORT_SYMBOL_GPL(ltt_channels_set_default);
 174
 175 /**
 176  * ltt_channels_get_name_from_index - get channel name from channel index
 177  * @index: channel index
 178  *
 179  * Allows to lookup the channel name given its index. Done to keep the name
 180  * information outside of each trace channel instance.
 181  */
 182 const char *ltt_channels_get_name_from_index(unsigned int index)
 183 {
 184         struct ltt_channel_setting *iter;
 185
 186         list_for_each_entry(iter, &ltt_channels, list)
 187                 if (iter->index == index && atomic_read(&iter->kref.refcount))
 188                         return iter->name;
 189         return NULL;
 190 }
 191 //ust// EXPORT_SYMBOL_GPL(ltt_channels_get_name_from_index);
 192
 193 static struct ltt_channel_setting *
 194 ltt_channels_get_setting_from_name(const char *name)
 195 {
 196         struct ltt_channel_setting *iter;
 197
 198         list_for_each_entry(iter, &ltt_channels, list)
 199                 if (!strcmp(iter->name, name)
 200                     && atomic_read(&iter->kref.refcount))
 201                         return iter;
 202         return NULL;
 203 }
 204
 205 /**
 206  * ltt_channels_get_index_from_name - get channel index from channel name
 207  * @name: channel name
 208  *
 209  * Allows to lookup the channel index given its name. Done to keep the name
 210  * information outside of each trace channel instance.
 211  * Returns -1 if not found.
 212  */
 213 int ltt_channels_get_index_from_name(const char *name)
 214 {
 215         struct ltt_channel_setting *setting;
 216
 217         setting = ltt_channels_get_setting_from_name(name);
 218         if (setting)
 219                 return setting->index;
 220         else
 221                 return -1;
 222 }
 223 //ust// EXPORT_SYMBOL_GPL(ltt_channels_get_index_from_name);
 224
 225 /**
 226  * ltt_channels_trace_alloc - Allocate channel structures for a trace
 227  * @subbuf_size: subbuffer size. 0 uses default.
 228  * @subbuf_cnt: number of subbuffers per per-cpu buffers. 0 uses default.
 229  * @flags: Default channel flags
 230  *
 231  * Use the current channel list to allocate the channels for a trace.
 232  * Called with trace lock held. Does not perform the trace buffer allocation,
 233  * because we must let the user overwrite specific channel sizes.
 234  */
 235 struct ltt_channel_struct *ltt_channels_trace_alloc(unsigned int *nr_channels,
 236                                                     int overwrite,
 237                                                     int active)
 238 {
 239         struct ltt_channel_struct *channel = NULL;
 240         struct ltt_channel_setting *iter;
 241
 242         mutex_lock(&ltt_channel_mutex);
 243         if (!free_index) {
 244                 WARN("ltt_channels_trace_alloc: no free_index; are there any probes connected?");
 245                 goto end;
 246         }
 247         if (!atomic_read(&index_kref.refcount))
 248                 kref_init(&index_kref);
 249         else
 250                 kref_get(&index_kref);
 251         *nr_channels = free_index;
 252         channel = kzalloc(sizeof(struct ltt_channel_struct) * free_index,
 253                           GFP_KERNEL);
 254         if (!channel) {
 255                 WARN("ltt_channel_struct: channel null after alloc");
 256                 goto end;
 257         }
 258         list_for_each_entry(iter, &ltt_channels, list) {
 259                 if (!atomic_read(&iter->kref.refcount))
 260                         continue;
 261                 channel[iter->index].subbuf_size = iter->subbuf_size;
 262                 channel[iter->index].subbuf_cnt = iter->subbuf_cnt;
 263                 channel[iter->index].overwrite = overwrite;
 264                 channel[iter->index].active = active;
 265                 channel[iter->index].channel_name = iter->name;
 266         }
 267 end:
 268         mutex_unlock(&ltt_channel_mutex);
 269         return channel;
 270 }
 271 //ust// EXPORT_SYMBOL_GPL(ltt_channels_trace_alloc);
 272
 273 /**
 274  * ltt_channels_trace_free - Free one trace's channels
 275  * @channels: channels to free
 276  *
 277  * Called with trace lock held. The actual channel buffers must be freed before
 278  * this function is called.
 279  */
 280 void ltt_channels_trace_free(struct ltt_channel_struct *channels)
 281 {
 282         lock_markers();
 283         mutex_lock(&ltt_channel_mutex);
 284         kfree(channels);
 285         kref_put(&index_kref, release_trace_channel);
 286         mutex_unlock(&ltt_channel_mutex);
 287         unlock_markers();
 288 }
 289 //ust// EXPORT_SYMBOL_GPL(ltt_channels_trace_free);
 290
 291 /**
 292  * _ltt_channels_get_event_id - get next event ID for a marker
 293  * @channel: channel name
 294  * @name: event name
 295  *
 296  * Returns a unique event ID (for this channel) or < 0 on error.
 297  * Must be called with channels mutex held.
 298  */
 299 int _ltt_channels_get_event_id(const char *channel, const char *name)
 300 {
 301         struct ltt_channel_setting *setting;
 302         int ret;
 303
 304         setting = ltt_channels_get_setting_from_name(channel);
 305         if (!setting) {
 306                 ret = -ENOENT;
 307                 goto end;
 308         }
 309         if (strcmp(channel, "metadata") == 0) {
 310                 if (strcmp(name, "core_marker_id") == 0)
 311                         ret = 0;
 312                 else if (strcmp(name, "core_marker_format") == 0)
 313                         ret = 1;
 314                 else
 315                         ret = -ENOENT;
 316                 goto end;
 317         }
 318         if (setting->free_event_id == EVENTS_PER_CHANNEL - 1) {
 319                 ret = -ENOSPC;
 320                 goto end;
 321         }
 322         ret = setting->free_event_id++;
 323 end:
 324         return ret;
 325 }
 326
 327 /**
 328  * ltt_channels_get_event_id - get next event ID for a marker
 329  * @channel: channel name
 330  * @name: event name
 331  *
 332  * Returns a unique event ID (for this channel) or < 0 on error.
 333  */
 334 int ltt_channels_get_event_id(const char *channel, const char *name)
 335 {
 336         int ret;
 337
 338         mutex_lock(&ltt_channel_mutex);
 339         ret = _ltt_channels_get_event_id(channel, name);
 340         mutex_unlock(&ltt_channel_mutex);
 341         return ret;
 342 }
 343
 344 //ust// MODULE_LICENSE("GPL");
 345 //ust// MODULE_AUTHOR("Mathieu Desnoyers");
 346 //ust// MODULE_DESCRIPTION("Linux Trace Toolkit Next Generation Channel Management");