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 //ust// #include <linux/module.h>
  27 //ust// #include <linux/ltt-channels.h>
  28 //ust// #include <linux/mutex.h>
  29 //ust// #include <linux/vmalloc.h>
  30
  31 #include "kernelcompat.h"
  32 #include "channels.h"
  33 #include "usterr.h"
  34
  35 /*
  36  * ltt_channel_mutex may be nested inside the LTT trace mutex.
  37  * ltt_channel_mutex mutex may be nested inside markers mutex.
  38  */
  39 static DEFINE_MUTEX(ltt_channel_mutex);
  40 static LIST_HEAD(ltt_channels);
  41 /*
  42  * Index of next channel in array. Makes sure that as long as a trace channel is
  43  * allocated, no array index will be re-used when a channel is freed and then
  44  * another channel is allocated. This index is cleared and the array indexeds
  45  * get reassigned when the index_kref goes back to 0, which indicates that no
  46  * more trace channels are allocated.
  47  */
  48 static unsigned int free_index;
  49 static struct kref index_kref;  /* Keeps track of allocated trace channels */
  50
  51 static struct ltt_channel_setting *lookup_channel(const char *name)
  52 {
  53         struct ltt_channel_setting *iter;
  54
  55         list_for_each_entry(iter, &ltt_channels, list)
  56                 if (strcmp(name, iter->name) == 0)
  57                         return iter;
  58         return NULL;
  59 }
  60
  61 /*
  62  * Must be called when channel refcount falls to 0 _and_ also when the last
  63  * trace is freed. This function is responsible for compacting the channel and
  64  * event IDs when no users are active.
  65  *
  66  * Called with lock_markers() and channels mutex held.
  67  */
  68 static void release_channel_setting(struct kref *kref)
  69 {
  70         struct ltt_channel_setting *setting = container_of(kref,
  71                 struct ltt_channel_setting, kref);
  72         struct ltt_channel_setting *iter;
  73
  74         if (atomic_read(&index_kref.refcount) == 0
  75             && atomic_read(&setting->kref.refcount) == 0) {
  76                 list_del(&setting->list);
  77                 kfree(setting);
  78
  79                 free_index = 0;
  80                 list_for_each_entry(iter, &ltt_channels, list) {
  81                         iter->index = free_index++;
  82                         iter->free_event_id = 0;
  83                 }
  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 kref *kref)
  94 {
  95         struct ltt_channel_setting *iter, *n;
  96
  97         list_for_each_entry_safe(iter, n, &ltt_channels, list)
  98                 release_channel_setting(&iter->kref);
  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         mutex_lock(&ltt_channel_mutex);
 113         setting = lookup_channel(name);
 114         if (setting) {
 115                 if (atomic_read(&setting->kref.refcount) == 0)
 116                         goto init_kref;
 117                 else {
 118                         kref_get(&setting->kref);
 119                         goto end;
 120                 }
 121         }
 122         setting = kzalloc(sizeof(*setting), GFP_KERNEL);
 123         if (!setting) {
 124                 ret = -ENOMEM;
 125                 goto end;
 126         }
 127         list_add(&setting->list, &ltt_channels);
 128         strncpy(setting->name, name, PATH_MAX-1);
 129         setting->index = free_index++;
 130 init_kref:
 131         kref_init(&setting->kref);
 132 end:
 133         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         mutex_lock(&ltt_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 end:
 157         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         mutex_lock(&ltt_channel_mutex);
 176         setting = lookup_channel(name);
 177         if (!setting || atomic_read(&setting->kref.refcount) == 0) {
 178                 ret = -ENOENT;
 179                 goto end;
 180         }
 181         setting->subbuf_size = subbuf_size;
 182         setting->subbuf_cnt = subbuf_cnt;
 183 end:
 184         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         list_for_each_entry(iter, &ltt_channels, list)
 201                 if (iter->index == index && atomic_read(&iter->kref.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         list_for_each_entry(iter, &ltt_channels, list)
 213                 if (!strcmp(iter->name, name)
 214                     && atomic_read(&iter->kref.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 ltt_channel_struct *ltt_channels_trace_alloc(unsigned int *nr_channels,
 250                                                     int overwrite,
 251                                                     int active)
 252 {
 253         struct ltt_channel_struct *channel = NULL;
 254         struct ltt_channel_setting *iter;
 255
 256         mutex_lock(&ltt_channel_mutex);
 257         if (!free_index) {
 258                 WARN("ltt_channels_trace_alloc: no free_index; are there any probes connected?");
 259                 goto end;
 260         }
 261         if (!atomic_read(&index_kref.refcount))
 262                 kref_init(&index_kref);
 263         else
 264                 kref_get(&index_kref);
 265         *nr_channels = free_index;
 266         channel = kzalloc(sizeof(struct ltt_channel_struct) * free_index,
 267                           GFP_KERNEL);
 268         if (!channel) {
 269                 WARN("ltt_channel_struct: channel null after alloc");
 270                 goto end;
 271         }
 272         list_for_each_entry(iter, &ltt_channels, list) {
 273                 if (!atomic_read(&iter->kref.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].active = active;
 279                 channel[iter->index].channel_name = iter->name;
 280         }
 281 end:
 282         mutex_unlock(&ltt_channel_mutex);
 283         return channel;
 284 }
 285 //ust// EXPORT_SYMBOL_GPL(ltt_channels_trace_alloc);
 286
 287 /**
 288  * ltt_channels_trace_free - Free one trace's channels
 289  * @channels: channels to free
 290  *
 291  * Called with trace lock held. The actual channel buffers must be freed before
 292  * this function is called.
 293  */
 294 void ltt_channels_trace_free(struct ltt_channel_struct *channels)
 295 {
 296         lock_markers();
 297         mutex_lock(&ltt_channel_mutex);
 298         kfree(channels);
 299         kref_put(&index_kref, release_trace_channel);
 300         mutex_unlock(&ltt_channel_mutex);
 301         unlock_markers();
 302 }
 303 //ust// EXPORT_SYMBOL_GPL(ltt_channels_trace_free);
 304
 305 /**
 306  * _ltt_channels_get_event_id - get next event ID for a marker
 307  * @channel: channel name
 308  * @name: event name
 309  *
 310  * Returns a unique event ID (for this channel) or < 0 on error.
 311  * Must be called with channels mutex held.
 312  */
 313 int _ltt_channels_get_event_id(const char *channel, const char *name)
 314 {
 315         struct ltt_channel_setting *setting;
 316         int ret;
 317
 318         setting = ltt_channels_get_setting_from_name(channel);
 319         if (!setting) {
 320                 ret = -ENOENT;
 321                 goto end;
 322         }
 323         if (strcmp(channel, "metadata") == 0) {
 324                 if (strcmp(name, "core_marker_id") == 0)
 325                         ret = 0;
 326                 else if (strcmp(name, "core_marker_format") == 0)
 327                         ret = 1;
 328                 else if (strcmp(name, "testev") == 0)
 329                         ret = 2;
 330                 else
 331                         ret = -ENOENT;
 332                 goto end;
 333         }
 334         if (setting->free_event_id == EVENTS_PER_CHANNEL - 1) {
 335                 ret = -ENOSPC;
 336                 goto end;
 337         }
 338         ret = setting->free_event_id++;
 339 end:
 340         return ret;
 341 }
 342
 343 /**
 344  * ltt_channels_get_event_id - get next event ID for a marker
 345  * @channel: channel name
 346  * @name: event name
 347  *
 348  * Returns a unique event ID (for this channel) or < 0 on error.
 349  */
 350 int ltt_channels_get_event_id(const char *channel, const char *name)
 351 {
 352         int ret;
 353
 354         mutex_lock(&ltt_channel_mutex);
 355         ret = _ltt_channels_get_event_id(channel, name);
 356         mutex_unlock(&ltt_channel_mutex);
 357         return ret;
 358 }
 359
 360 //ust// MODULE_LICENSE("GPL");
 361 //ust// MODULE_AUTHOR("Mathieu Desnoyers");
 362 //ust// MODULE_DESCRIPTION("Linux Trace Toolkit Next Generation Channel Management");