src/side.c

   1 // SPDX-License-Identifier: MIT
   2 /*
   3  * Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  */
   5
   6 #include <side/trace.h>
   7 #include <string.h>
   8 #include <assert.h>
   9
  10 #include "rcu.h"
  11 #include "list.h"
  12 #include "rculist.h"
  13
  14 /* Top 8 bits reserved for shared tracer use. */
  15 #if SIDE_BITS_PER_LONG == 64
  16 # define SIDE_EVENT_ENABLED_SHARED_MASK                 0xFF00000000000000ULL
  17 # define SIDE_EVENT_ENABLED_SHARED_USER_EVENT_MASK      0x8000000000000000ULL
  18 # define SIDE_EVENT_ENABLED_SHARED_PTRACE_MASK          0x4000000000000000ULL
  19
  20 /* Allow 2^56 private tracer references on an event. */
  21 # define SIDE_EVENT_ENABLED_PRIVATE_MASK                0x00FFFFFFFFFFFFFFULL
  22 #else
  23 # define SIDE_EVENT_ENABLED_SHARED_MASK                 0xFF000000UL
  24 # define SIDE_EVENT_ENABLED_SHARED_USER_EVENT_MASK      0x80000000UL
  25 # define SIDE_EVENT_ENABLED_SHARED_PTRACE_MASK          0x40000000UL
  26
  27 /* Allow 2^24 private tracer references on an event. */
  28 # define SIDE_EVENT_ENABLED_PRIVATE_MASK                0x00FFFFFFUL
  29 #endif
  30
  31 /* Key 0x1 is reserved for user event. */
  32 #define SIDE_USER_EVENT_KEY                             ((void *)0x1UL)
  33 /* Key 0x2 is reserved for ptrace. */
  34 #define SIDE_PTRACE_KEY                                 ((void *)0x2UL)
  35
  36 struct side_events_register_handle {
  37         struct side_list_node node;
  38         struct side_event_description **events;
  39         uint32_t nr_events;
  40 };
  41
  42 struct side_tracer_handle {
  43         struct side_list_node node;
  44         void (*cb)(enum side_tracer_notification notif,
  45                 struct side_event_description **events, uint32_t nr_events, void *priv);
  46         void *priv;
  47 };
  48
  49 struct side_statedump_request_handle {
  50         struct side_list_node node;     /* RCU list. */
  51         void (*cb)(void);
  52 };
  53
  54 struct side_callback {
  55         union {
  56                 void (*call)(const struct side_event_description *desc,
  57                         const struct side_arg_vec *side_arg_vec,
  58                         void *priv);
  59                 void (*call_variadic)(const struct side_event_description *desc,
  60                         const struct side_arg_vec *side_arg_vec,
  61                         const struct side_arg_dynamic_struct *var_struct,
  62                         void *priv);
  63         } u;
  64         void *priv;
  65         void *key;
  66 };
  67
  68 static struct side_rcu_gp_state event_rcu_gp, statedump_rcu_gp;
  69
  70 /*
  71  * Lazy initialization for early use within library constructors.
  72  */
  73 static bool initialized;
  74 /*
  75  * Do not register/unregister any more events after destructor.
  76  */
  77 static bool finalized;
  78
  79 /*
  80  * Recursive mutex to allow tracer callbacks to use the side API.
  81  */
  82 static pthread_mutex_t side_event_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
  83 static pthread_mutex_t side_statedump_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
  84
  85 static DEFINE_SIDE_LIST_HEAD(side_events_list);
  86 static DEFINE_SIDE_LIST_HEAD(side_tracer_list);
  87 static DEFINE_SIDE_LIST_HEAD(side_statedump_list);
  88
  89 /*
  90  * Callback filter key for state dump.
  91  */
  92 static __thread void *filter_key;
  93
  94 /*
  95  * The empty callback has a NULL function callback pointer, which stops
  96  * iteration on the array of callbacks immediately.
  97  */
  98 const char side_empty_callback[sizeof(struct side_callback)];
  99
 100 /*
 101  * side_ptrace_hook is a place holder for a debugger breakpoint.
 102  * var_struct is NULL if not variadic.
 103  */
 104 void side_ptrace_hook(const struct side_event_state *event_state __attribute__((unused)),
 105         const struct side_arg_vec *side_arg_vec __attribute__((unused)),
 106         const struct side_arg_dynamic_struct *var_struct __attribute__((unused)))
 107         __attribute__((noinline));
 108 void side_ptrace_hook(const struct side_event_state *event_state __attribute__((unused)),
 109         const struct side_arg_vec *side_arg_vec __attribute__((unused)),
 110         const struct side_arg_dynamic_struct *var_struct __attribute__((unused)))
 111 {
 112 }
 113
 114 static
 115 void _side_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec, void *key)
 116 {
 117         struct side_rcu_read_state rcu_read_state;
 118         const struct side_event_state_0 *es0;
 119         const struct side_callback *side_cb;
 120         uintptr_t enabled;
 121
 122         if (side_unlikely(finalized))
 123                 return;
 124         if (side_unlikely(!initialized))
 125                 side_init();
 126         if (side_unlikely(event_state->version != 0))
 127                 abort();
 128         es0 = side_container_of(event_state, const struct side_event_state_0, parent);
 129         assert(!(es0->desc->flags & SIDE_EVENT_FLAG_VARIADIC));
 130         enabled = __atomic_load_n(&es0->enabled, __ATOMIC_RELAXED);
 131         if (side_unlikely(enabled & SIDE_EVENT_ENABLED_SHARED_MASK)) {
 132                 if ((enabled & SIDE_EVENT_ENABLED_SHARED_USER_EVENT_MASK) &&
 133                     (!key || key == SIDE_USER_EVENT_KEY)) {
 134                         // TODO: call kernel write.
 135                 }
 136                 if ((enabled & SIDE_EVENT_ENABLED_SHARED_PTRACE_MASK) &&
 137                     (!key || key == SIDE_PTRACE_KEY))
 138                         side_ptrace_hook(event_state, side_arg_vec, NULL);
 139         }
 140         side_rcu_read_begin(&event_rcu_gp, &rcu_read_state);
 141         for (side_cb = side_rcu_dereference(es0->callbacks); side_cb->u.call != NULL; side_cb++) {
 142                 /* A NULL key is always a match. */
 143                 if (key && side_cb->key && side_cb->key != key)
 144                         continue;
 145                 side_cb->u.call(es0->desc, side_arg_vec, side_cb->priv);
 146         }
 147         side_rcu_read_end(&event_rcu_gp, &rcu_read_state);
 148 }
 149
 150 void side_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec)
 151 {
 152         _side_call(event_state, side_arg_vec, NULL);
 153 }
 154
 155 void side_statedump_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec)
 156 {
 157         _side_call(event_state, side_arg_vec, filter_key);
 158 }
 159
 160 static
 161 void _side_call_variadic(const struct side_event_state *event_state,
 162         const struct side_arg_vec *side_arg_vec,
 163         const struct side_arg_dynamic_struct *var_struct,
 164         void *key)
 165 {
 166         struct side_rcu_read_state rcu_read_state;
 167         const struct side_event_state_0 *es0;
 168         const struct side_callback *side_cb;
 169         uintptr_t enabled;
 170
 171         if (side_unlikely(finalized))
 172                 return;
 173         if (side_unlikely(!initialized))
 174                 side_init();
 175         if (side_unlikely(event_state->version != 0))
 176                 abort();
 177         es0 = side_container_of(event_state, const struct side_event_state_0, parent);
 178         assert(es0->desc->flags & SIDE_EVENT_FLAG_VARIADIC);
 179         enabled = __atomic_load_n(&es0->enabled, __ATOMIC_RELAXED);
 180         if (side_unlikely(enabled & SIDE_EVENT_ENABLED_SHARED_MASK)) {
 181                 if ((enabled & SIDE_EVENT_ENABLED_SHARED_USER_EVENT_MASK) &&
 182                     (!key || key == SIDE_USER_EVENT_KEY)) {
 183                         // TODO: call kernel write.
 184                 }
 185                 if ((enabled & SIDE_EVENT_ENABLED_SHARED_PTRACE_MASK) &&
 186                     (!key || key == SIDE_PTRACE_KEY))
 187                         side_ptrace_hook(event_state, side_arg_vec, var_struct);
 188         }
 189         side_rcu_read_begin(&event_rcu_gp, &rcu_read_state);
 190         for (side_cb = side_rcu_dereference(es0->callbacks); side_cb->u.call_variadic != NULL; side_cb++) {
 191                 /* A NULL key is always a match. */
 192                 if (key && side_cb->key && side_cb->key != key)
 193                         continue;
 194                 side_cb->u.call_variadic(es0->desc, side_arg_vec, var_struct, side_cb->priv);
 195         }
 196         side_rcu_read_end(&event_rcu_gp, &rcu_read_state);
 197 }
 198
 199 void side_call_variadic(const struct side_event_state *event_state,
 200         const struct side_arg_vec *side_arg_vec,
 201         const struct side_arg_dynamic_struct *var_struct)
 202 {
 203         _side_call_variadic(event_state, side_arg_vec, var_struct, NULL);
 204 }
 205
 206 void side_statedump_call_variadic(const struct side_event_state *event_state,
 207         const struct side_arg_vec *side_arg_vec,
 208         const struct side_arg_dynamic_struct *var_struct)
 209 {
 210         _side_call_variadic(event_state, side_arg_vec, var_struct, filter_key);
 211 }
 212
 213 static
 214 const struct side_callback *side_tracer_callback_lookup(
 215                 const struct side_event_description *desc,
 216                 void *call, void *priv, void *key)
 217 {
 218         struct side_event_state *event_state = side_ptr_get(desc->state);
 219         const struct side_event_state_0 *es0;
 220         const struct side_callback *cb;
 221
 222         if (side_unlikely(event_state->version != 0))
 223                 abort();
 224         es0 = side_container_of(event_state, const struct side_event_state_0, parent);
 225         for (cb = es0->callbacks; cb->u.call != NULL; cb++) {
 226                 if ((void *) cb->u.call == call && cb->priv == priv && cb->key == key)
 227                         return cb;
 228         }
 229         return NULL;
 230 }
 231
 232 static
 233 int _side_tracer_callback_register(struct side_event_description *desc,
 234                 void *call, void *priv, void *key)
 235 {
 236         struct side_event_state *event_state;
 237         struct side_callback *old_cb, *new_cb;
 238         struct side_event_state_0 *es0;
 239         int ret = SIDE_ERROR_OK;
 240         uint32_t old_nr_cb;
 241
 242         if (!call)
 243                 return SIDE_ERROR_INVAL;
 244         if (finalized)
 245                 return SIDE_ERROR_EXITING;
 246         if (!initialized)
 247                 side_init();
 248         pthread_mutex_lock(&side_event_lock);
 249         event_state = side_ptr_get(desc->state);
 250         if (side_unlikely(event_state->version != 0))
 251                 abort();
 252         es0 = side_container_of(event_state, struct side_event_state_0, parent);
 253         old_nr_cb = es0->nr_callbacks;
 254         if (old_nr_cb == UINT32_MAX) {
 255                 ret = SIDE_ERROR_INVAL;
 256                 goto unlock;
 257         }
 258         /* Reject duplicate (call, priv) tuples. */
 259         if (side_tracer_callback_lookup(desc, call, priv, key)) {
 260                 ret = SIDE_ERROR_EXIST;
 261                 goto unlock;
 262         }
 263         old_cb = (struct side_callback *) es0->callbacks;
 264         /* old_nr_cb + 1 (new cb) + 1 (NULL) */
 265         new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
 266         if (!new_cb) {
 267                 ret = SIDE_ERROR_NOMEM;
 268                 goto unlock;
 269         }
 270         memcpy(new_cb, old_cb, old_nr_cb);
 271         if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
 272                 new_cb[old_nr_cb].u.call_variadic =
 273                         (side_tracer_callback_variadic_func) call;
 274         else
 275                 new_cb[old_nr_cb].u.call =
 276                         (side_tracer_callback_func) call;
 277         new_cb[old_nr_cb].priv = priv;
 278         new_cb[old_nr_cb].key = key;
 279         /* High order bits are already zeroed. */
 280         side_rcu_assign_pointer(es0->callbacks, new_cb);
 281         side_rcu_wait_grace_period(&event_rcu_gp);
 282         if (old_nr_cb)
 283                 free(old_cb);
 284         es0->nr_callbacks++;
 285         /* Increment concurrently with kernel setting the top bits. */
 286         if (!old_nr_cb)
 287                 (void) __atomic_add_fetch(&es0->enabled, 1, __ATOMIC_RELAXED);
 288 unlock:
 289         pthread_mutex_unlock(&side_event_lock);
 290         return ret;
 291 }
 292
 293 int side_tracer_callback_register(struct side_event_description *desc,
 294                 side_tracer_callback_func call,
 295                 void *priv, void *key)
 296 {
 297         if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
 298                 return SIDE_ERROR_INVAL;
 299         return _side_tracer_callback_register(desc, (void *) call, priv, key);
 300 }
 301
 302 int side_tracer_callback_variadic_register(struct side_event_description *desc,
 303                 side_tracer_callback_variadic_func call_variadic,
 304                 void *priv, void *key)
 305 {
 306         if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
 307                 return SIDE_ERROR_INVAL;
 308         return _side_tracer_callback_register(desc, (void *) call_variadic, priv, key);
 309 }
 310
 311 static int _side_tracer_callback_unregister(struct side_event_description *desc,
 312                 void *call, void *priv, void *key)
 313 {
 314         struct side_event_state *event_state;
 315         struct side_callback *old_cb, *new_cb;
 316         const struct side_callback *cb_pos;
 317         struct side_event_state_0 *es0;
 318         uint32_t pos_idx;
 319         int ret = SIDE_ERROR_OK;
 320         uint32_t old_nr_cb;
 321
 322         if (!call)
 323                 return SIDE_ERROR_INVAL;
 324         if (finalized)
 325                 return SIDE_ERROR_EXITING;
 326         if (!initialized)
 327                 side_init();
 328         pthread_mutex_lock(&side_event_lock);
 329         event_state = side_ptr_get(desc->state);
 330         if (side_unlikely(event_state->version != 0))
 331                 abort();
 332         es0 = side_container_of(event_state, struct side_event_state_0, parent);
 333         cb_pos = side_tracer_callback_lookup(desc, call, priv, key);
 334         if (!cb_pos) {
 335                 ret = SIDE_ERROR_NOENT;
 336                 goto unlock;
 337         }
 338         old_nr_cb = es0->nr_callbacks;
 339         old_cb = (struct side_callback *) es0->callbacks;
 340         if (old_nr_cb == 1) {
 341                 new_cb = (struct side_callback *) &side_empty_callback;
 342         } else {
 343                 pos_idx = cb_pos - es0->callbacks;
 344                 /* Remove entry at pos_idx. */
 345                 /* old_nr_cb - 1 (removed cb) + 1 (NULL) */
 346                 new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
 347                 if (!new_cb) {
 348                         ret = SIDE_ERROR_NOMEM;
 349                         goto unlock;
 350                 }
 351                 memcpy(new_cb, old_cb, pos_idx);
 352                 memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
 353         }
 354         /* High order bits are already zeroed. */
 355         side_rcu_assign_pointer(es0->callbacks, new_cb);
 356         side_rcu_wait_grace_period(&event_rcu_gp);
 357         free(old_cb);
 358         es0->nr_callbacks--;
 359         /* Decrement concurrently with kernel setting the top bits. */
 360         if (old_nr_cb == 1)
 361                 (void) __atomic_add_fetch(&es0->enabled, -1, __ATOMIC_RELAXED);
 362 unlock:
 363         pthread_mutex_unlock(&side_event_lock);
 364         return ret;
 365 }
 366
 367 int side_tracer_callback_unregister(struct side_event_description *desc,
 368                 side_tracer_callback_func call,
 369                 void *priv, void *key)
 370 {
 371         if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
 372                 return SIDE_ERROR_INVAL;
 373         return _side_tracer_callback_unregister(desc, (void *) call, priv, key);
 374 }
 375
 376 int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
 377                 side_tracer_callback_variadic_func call_variadic,
 378                 void *priv, void *key)
 379 {
 380         if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
 381                 return SIDE_ERROR_INVAL;
 382         return _side_tracer_callback_unregister(desc, (void *) call_variadic, priv, key);
 383 }
 384
 385 struct side_events_register_handle *side_events_register(struct side_event_description **events, uint32_t nr_events)
 386 {
 387         struct side_events_register_handle *events_handle = NULL;
 388         struct side_tracer_handle *tracer_handle;
 389
 390         if (finalized)
 391                 return NULL;
 392         if (!initialized)
 393                 side_init();
 394         events_handle = (struct side_events_register_handle *)
 395                         calloc(1, sizeof(struct side_events_register_handle));
 396         if (!events_handle)
 397                 return NULL;
 398         events_handle->events = events;
 399         events_handle->nr_events = nr_events;
 400
 401         pthread_mutex_lock(&side_event_lock);
 402         side_list_insert_node_tail(&side_events_list, &events_handle->node);
 403         side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
 404                 tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
 405                         events, nr_events, tracer_handle->priv);
 406         }
 407         pthread_mutex_unlock(&side_event_lock);
 408         //TODO: call event batch register ioctl
 409         return events_handle;
 410 }
 411
 412 static
 413 void side_event_remove_callbacks(struct side_event_description *desc)
 414 {
 415         struct side_event_state *event_state = side_ptr_get(desc->state);
 416         struct side_event_state_0 *es0;
 417         struct side_callback *old_cb;
 418         uint32_t nr_cb;
 419
 420         if (side_unlikely(event_state->version != 0))
 421                 abort();
 422         es0 = side_container_of(event_state, struct side_event_state_0, parent);
 423         nr_cb = es0->nr_callbacks;
 424         if (!nr_cb)
 425                 return;
 426         old_cb = (struct side_callback *) es0->callbacks;
 427         (void) __atomic_add_fetch(&es0->enabled, -1, __ATOMIC_RELAXED);
 428         /*
 429          * Setting the state back to 0 cb and empty callbacks out of
 430          * caution. This should not matter because instrumentation is
 431          * unreachable.
 432          */
 433         es0->nr_callbacks = 0;
 434         side_rcu_assign_pointer(es0->callbacks, &side_empty_callback);
 435         /*
 436          * No need to wait for grace period because instrumentation is
 437          * unreachable.
 438          */
 439         free(old_cb);
 440 }
 441
 442 /*
 443  * Unregister event handle. At this point, all side events in that
 444  * handle should be unreachable.
 445  */
 446 void side_events_unregister(struct side_events_register_handle *events_handle)
 447 {
 448         struct side_tracer_handle *tracer_handle;
 449         uint32_t i;
 450
 451         if (!events_handle)
 452                 return;
 453         if (finalized)
 454                 return;
 455         if (!initialized)
 456                 side_init();
 457         pthread_mutex_lock(&side_event_lock);
 458         side_list_remove_node(&events_handle->node);
 459         side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
 460                 tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
 461                         events_handle->events, events_handle->nr_events,
 462                         tracer_handle->priv);
 463         }
 464         for (i = 0; i < events_handle->nr_events; i++) {
 465                 struct side_event_description *event = events_handle->events[i];
 466
 467                 /* Skip NULL pointers */
 468                 if (!event)
 469                         continue;
 470                 side_event_remove_callbacks(event);
 471         }
 472         pthread_mutex_unlock(&side_event_lock);
 473         //TODO: call event batch unregister ioctl
 474         free(events_handle);
 475 }
 476
 477 struct side_tracer_handle *side_tracer_event_notification_register(
 478                 void (*cb)(enum side_tracer_notification notif,
 479                         struct side_event_description **events, uint32_t nr_events, void *priv),
 480                 void *priv)
 481 {
 482         struct side_tracer_handle *tracer_handle;
 483         struct side_events_register_handle *events_handle;
 484
 485         if (finalized)
 486                 return NULL;
 487         if (!initialized)
 488                 side_init();
 489         tracer_handle = (struct side_tracer_handle *)
 490                                 calloc(1, sizeof(struct side_tracer_handle));
 491         if (!tracer_handle)
 492                 return NULL;
 493         pthread_mutex_lock(&side_event_lock);
 494         tracer_handle->cb = cb;
 495         tracer_handle->priv = priv;
 496         side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
 497         side_list_for_each_entry(events_handle, &side_events_list, node) {
 498                 cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
 499                         events_handle->events, events_handle->nr_events, priv);
 500         }
 501         pthread_mutex_unlock(&side_event_lock);
 502         return tracer_handle;
 503 }
 504
 505 void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
 506 {
 507         struct side_events_register_handle *events_handle;
 508
 509         if (finalized)
 510                 return;
 511         if (!initialized)
 512                 side_init();
 513         pthread_mutex_lock(&side_event_lock);
 514         side_list_for_each_entry(events_handle, &side_events_list, node) {
 515                 tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
 516                         events_handle->events, events_handle->nr_events,
 517                         tracer_handle->priv);
 518         }
 519         side_list_remove_node(&tracer_handle->node);
 520         pthread_mutex_unlock(&side_event_lock);
 521         free(tracer_handle);
 522 }
 523
 524 struct side_statedump_request_handle *side_statedump_request_notification_register(void (*statedump_cb)(void))
 525 {
 526         struct side_statedump_request_handle *handle;
 527
 528         if (finalized)
 529                 return NULL;
 530         if (!initialized)
 531                 side_init();
 532         /*
 533          * The statedump request notification should not be registered
 534          * from a notification callback.
 535          */
 536         assert(filter_key == NULL);
 537         handle = (struct side_statedump_request_handle *)
 538                                 calloc(1, sizeof(struct side_statedump_request_handle));
 539         if (!handle)
 540                 return NULL;
 541         handle->cb = statedump_cb;
 542
 543         pthread_mutex_lock(&side_statedump_lock);
 544         side_list_insert_node_tail_rcu(&side_statedump_list, &handle->node);
 545         pthread_mutex_unlock(&side_statedump_lock);
 546
 547         /* Invoke callback for all tracers. */
 548         statedump_cb();
 549
 550         return handle;
 551 }
 552
 553 void side_statedump_request_notification_unregister(struct side_statedump_request_handle *handle)
 554 {
 555         if (finalized)
 556                 return;
 557         if (!initialized)
 558                 side_init();
 559         assert(filter_key == NULL);
 560
 561         pthread_mutex_lock(&side_statedump_lock);
 562         side_list_remove_node_rcu(&handle->node);
 563         pthread_mutex_unlock(&side_statedump_lock);
 564
 565         side_rcu_wait_grace_period(&statedump_rcu_gp);
 566         free(handle);
 567 }
 568
 569 void side_tracer_statedump_request(void *key)
 570 {
 571         struct side_statedump_request_handle *handle;
 572         struct side_rcu_read_state rcu_read_state;
 573
 574         /* Invoke the state dump callback specifically for the tracer key. */
 575         filter_key = key;
 576         side_rcu_read_begin(&statedump_rcu_gp, &rcu_read_state);
 577         side_list_for_each_entry_rcu(handle, &side_statedump_list, node)
 578                 handle->cb();
 579         side_rcu_read_end(&statedump_rcu_gp, &rcu_read_state);
 580         filter_key = NULL;
 581 }
 582
 583 void side_init(void)
 584 {
 585         if (initialized)
 586                 return;
 587         side_rcu_gp_init(&event_rcu_gp);
 588         side_rcu_gp_init(&statedump_rcu_gp);
 589         initialized = true;
 590 }
 591
 592 /*
 593  * side_exit() is executed from a library destructor. It can be called
 594  * explicitly at application exit as well. Concurrent side API use is
 595  * not expected at that point.
 596  */
 597 void side_exit(void)
 598 {
 599         struct side_events_register_handle *handle, *tmp;
 600
 601         if (finalized)
 602                 return;
 603         side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
 604                 side_events_unregister(handle);
 605         side_rcu_gp_exit(&event_rcu_gp);
 606         side_rcu_gp_exit(&statedump_rcu_gp);
 607         finalized = true;
 608 }