libevent/evthread.c

   1 /*
   2  * Copyright (c) 2008-2012 Niels Provos, Nick Mathewson
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  * 3. The name of the author may not be used to endorse or promote products
  13  *    derived from this software without specific prior written permission.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "event2/event-config.h"
  28
  29 #ifndef _EVENT_DISABLE_THREAD_SUPPORT
  30
  31 #include "event2/thread.h"
  32
  33 #include <stdlib.h>
  34 #include <string.h>
  35
  36 #include "log-internal.h"
  37 #include "mm-internal.h"
  38 #include "util-internal.h"
  39 #include "evthread-internal.h"
  40
  41 #ifdef EVTHREAD_EXPOSE_STRUCTS
  42 #define GLOBAL
  43 #else
  44 #define GLOBAL static
  45 #endif
  46
  47 /* globals */
  48 GLOBAL int _evthread_lock_debugging_enabled = 0;
  49 GLOBAL struct evthread_lock_callbacks _evthread_lock_fns = {
  50         0, 0, NULL, NULL, NULL, NULL
  51 };
  52 GLOBAL unsigned long (*_evthread_id_fn)(void) = NULL;
  53 GLOBAL struct evthread_condition_callbacks _evthread_cond_fns = {
  54         0, NULL, NULL, NULL, NULL
  55 };
  56
  57 /* Used for debugging */
  58 static struct evthread_lock_callbacks _original_lock_fns = {
  59         0, 0, NULL, NULL, NULL, NULL
  60 };
  61 static struct evthread_condition_callbacks _original_cond_fns = {
  62         0, NULL, NULL, NULL, NULL
  63 };
  64
  65 void
  66 evthread_set_id_callback(unsigned long (*id_fn)(void))
  67 {
  68         _evthread_id_fn = id_fn;
  69 }
  70
  71 int
  72 evthread_set_lock_callbacks(const struct evthread_lock_callbacks *cbs)
  73 {
  74         struct evthread_lock_callbacks *target =
  75             _evthread_lock_debugging_enabled
  76             ? &_original_lock_fns : &_evthread_lock_fns;
  77
  78         if (!cbs) {
  79                 if (target->alloc)
  80                         event_warnx("Trying to disable lock functions after "
  81                             "they have been set up will probaby not work.");
  82                 memset(target, 0, sizeof(_evthread_lock_fns));
  83                 return 0;
  84         }
  85         if (target->alloc) {
  86                 /* Uh oh; we already had locking callbacks set up.*/
  87                 if (target->lock_api_version == cbs->lock_api_version &&
  88                         target->supported_locktypes == cbs->supported_locktypes &&
  89                         target->alloc == cbs->alloc &&
  90                         target->free == cbs->free &&
  91                         target->lock == cbs->lock &&
  92                         target->unlock == cbs->unlock) {
  93                         /* no change -- allow this. */
  94                         return 0;
  95                 }
  96                 event_warnx("Can't change lock callbacks once they have been "
  97                     "initialized.");
  98                 return -1;
  99         }
 100         if (cbs->alloc && cbs->free && cbs->lock && cbs->unlock) {
 101                 memcpy(target, cbs, sizeof(_evthread_lock_fns));
 102                 return event_global_setup_locks_(1);
 103         } else {
 104                 return -1;
 105         }
 106 }
 107
 108 int
 109 evthread_set_condition_callbacks(const struct evthread_condition_callbacks *cbs)
 110 {
 111         struct evthread_condition_callbacks *target =
 112             _evthread_lock_debugging_enabled
 113             ? &_original_cond_fns : &_evthread_cond_fns;
 114
 115         if (!cbs) {
 116                 if (target->alloc_condition)
 117                         event_warnx("Trying to disable condition functions "
 118                             "after they have been set up will probaby not "
 119                             "work.");
 120                 memset(target, 0, sizeof(_evthread_cond_fns));
 121                 return 0;
 122         }
 123         if (target->alloc_condition) {
 124                 /* Uh oh; we already had condition callbacks set up.*/
 125                 if (target->condition_api_version == cbs->condition_api_version &&
 126                         target->alloc_condition == cbs->alloc_condition &&
 127                         target->free_condition == cbs->free_condition &&
 128                         target->signal_condition == cbs->signal_condition &&
 129                         target->wait_condition == cbs->wait_condition) {
 130                         /* no change -- allow this. */
 131                         return 0;
 132                 }
 133                 event_warnx("Can't change condition callbacks once they "
 134                     "have been initialized.");
 135                 return -1;
 136         }
 137         if (cbs->alloc_condition && cbs->free_condition &&
 138             cbs->signal_condition && cbs->wait_condition) {
 139                 memcpy(target, cbs, sizeof(_evthread_cond_fns));
 140         }
 141         if (_evthread_lock_debugging_enabled) {
 142                 _evthread_cond_fns.alloc_condition = cbs->alloc_condition;
 143                 _evthread_cond_fns.free_condition = cbs->free_condition;
 144                 _evthread_cond_fns.signal_condition = cbs->signal_condition;
 145         }
 146         return 0;
 147 }
 148
 149 struct debug_lock {
 150         unsigned locktype;
 151         unsigned long held_by;
 152         /* XXXX if we ever use read-write locks, we will need a separate
 153          * lock to protect count. */
 154         int count;
 155         void *lock;
 156 };
 157
 158 static void *
 159 debug_lock_alloc(unsigned locktype)
 160 {
 161         struct debug_lock *result = mm_malloc(sizeof(struct debug_lock));
 162         if (!result)
 163                 return NULL;
 164         if (_original_lock_fns.alloc) {
 165                 if (!(result->lock = _original_lock_fns.alloc(
 166                                 locktype|EVTHREAD_LOCKTYPE_RECURSIVE))) {
 167                         mm_free(result);
 168                         return NULL;
 169                 }
 170         } else {
 171                 result->lock = NULL;
 172         }
 173         result->locktype = locktype;
 174         result->count = 0;
 175         result->held_by = 0;
 176         return result;
 177 }
 178
 179 static void
 180 debug_lock_free(void *lock_, unsigned locktype)
 181 {
 182         struct debug_lock *lock = lock_;
 183         EVUTIL_ASSERT(lock->count == 0);
 184         EVUTIL_ASSERT(locktype == lock->locktype);
 185         if (_original_lock_fns.free) {
 186                 _original_lock_fns.free(lock->lock,
 187                     lock->locktype|EVTHREAD_LOCKTYPE_RECURSIVE);
 188         }
 189         lock->lock = NULL;
 190         lock->count = -100;
 191         mm_free(lock);
 192 }
 193
 194 static void
 195 evthread_debug_lock_mark_locked(unsigned mode, struct debug_lock *lock)
 196 {
 197         ++lock->count;
 198         if (!(lock->locktype & EVTHREAD_LOCKTYPE_RECURSIVE))
 199                 EVUTIL_ASSERT(lock->count == 1);
 200         if (_evthread_id_fn) {
 201                 unsigned long me;
 202                 me = _evthread_id_fn();
 203                 if (lock->count > 1)
 204                         EVUTIL_ASSERT(lock->held_by == me);
 205                 lock->held_by = me;
 206         }
 207 }
 208
 209 static int
 210 debug_lock_lock(unsigned mode, void *lock_)
 211 {
 212         struct debug_lock *lock = lock_;
 213         int res = 0;
 214         if (lock->locktype & EVTHREAD_LOCKTYPE_READWRITE)
 215                 EVUTIL_ASSERT(mode & (EVTHREAD_READ|EVTHREAD_WRITE));
 216         else
 217                 EVUTIL_ASSERT((mode & (EVTHREAD_READ|EVTHREAD_WRITE)) == 0);
 218         if (_original_lock_fns.lock)
 219                 res = _original_lock_fns.lock(mode, lock->lock);
 220         if (!res) {
 221                 evthread_debug_lock_mark_locked(mode, lock);
 222         }
 223         return res;
 224 }
 225
 226 static void
 227 evthread_debug_lock_mark_unlocked(unsigned mode, struct debug_lock *lock)
 228 {
 229         if (lock->locktype & EVTHREAD_LOCKTYPE_READWRITE)
 230                 EVUTIL_ASSERT(mode & (EVTHREAD_READ|EVTHREAD_WRITE));
 231         else
 232                 EVUTIL_ASSERT((mode & (EVTHREAD_READ|EVTHREAD_WRITE)) == 0);
 233         if (_evthread_id_fn) {
 234                 EVUTIL_ASSERT(lock->held_by == _evthread_id_fn());
 235                 if (lock->count == 1)
 236                         lock->held_by = 0;
 237         }
 238         --lock->count;
 239         EVUTIL_ASSERT(lock->count >= 0);
 240 }
 241
 242 static int
 243 debug_lock_unlock(unsigned mode, void *lock_)
 244 {
 245         struct debug_lock *lock = lock_;
 246         int res = 0;
 247         evthread_debug_lock_mark_unlocked(mode, lock);
 248         if (_original_lock_fns.unlock)
 249                 res = _original_lock_fns.unlock(mode, lock->lock);
 250         return res;
 251 }
 252
 253 static int
 254 debug_cond_wait(void *_cond, void *_lock, const struct timeval *tv)
 255 {
 256         int r;
 257         struct debug_lock *lock = _lock;
 258         EVUTIL_ASSERT(lock);
 259         EVLOCK_ASSERT_LOCKED(_lock);
 260         evthread_debug_lock_mark_unlocked(0, lock);
 261         r = _original_cond_fns.wait_condition(_cond, lock->lock, tv);
 262         evthread_debug_lock_mark_locked(0, lock);
 263         return r;
 264 }
 265
 266 void
 267 evthread_enable_lock_debuging(void)
 268 {
 269         struct evthread_lock_callbacks cbs = {
 270                 EVTHREAD_LOCK_API_VERSION,
 271                 EVTHREAD_LOCKTYPE_RECURSIVE,
 272                 debug_lock_alloc,
 273                 debug_lock_free,
 274                 debug_lock_lock,
 275                 debug_lock_unlock
 276         };
 277         if (_evthread_lock_debugging_enabled)
 278                 return;
 279         memcpy(&_original_lock_fns, &_evthread_lock_fns,
 280             sizeof(struct evthread_lock_callbacks));
 281         memcpy(&_evthread_lock_fns, &cbs,
 282             sizeof(struct evthread_lock_callbacks));
 283
 284         memcpy(&_original_cond_fns, &_evthread_cond_fns,
 285             sizeof(struct evthread_condition_callbacks));
 286         _evthread_cond_fns.wait_condition = debug_cond_wait;
 287         _evthread_lock_debugging_enabled = 1;
 288
 289         /* XXX return value should get checked. */
 290         event_global_setup_locks_(0);
 291 }
 292
 293 int
 294 _evthread_is_debug_lock_held(void *lock_)
 295 {
 296         struct debug_lock *lock = lock_;
 297         if (! lock->count)
 298                 return 0;
 299         if (_evthread_id_fn) {
 300                 unsigned long me = _evthread_id_fn();
 301                 if (lock->held_by != me)
 302                         return 0;
 303         }
 304         return 1;
 305 }
 306
 307 void *
 308 _evthread_debug_get_real_lock(void *lock_)
 309 {
 310         struct debug_lock *lock = lock_;
 311         return lock->lock;
 312 }
 313
 314 void *
 315 evthread_setup_global_lock_(void *lock_, unsigned locktype, int enable_locks)
 316 {
 317         /* there are four cases here:
 318            1) we're turning on debugging; locking is not on.
 319            2) we're turning on debugging; locking is on.
 320            3) we're turning on locking; debugging is not on.
 321            4) we're turning on locking; debugging is on. */
 322
 323         if (!enable_locks && _original_lock_fns.alloc == NULL) {
 324                 /* Case 1: allocate a debug lock. */
 325                 EVUTIL_ASSERT(lock_ == NULL);
 326                 return debug_lock_alloc(locktype);
 327         } else if (!enable_locks && _original_lock_fns.alloc != NULL) {
 328                 /* Case 2: wrap the lock in a debug lock. */
 329                 struct debug_lock *lock;
 330                 EVUTIL_ASSERT(lock_ != NULL);
 331
 332                 if (!(locktype & EVTHREAD_LOCKTYPE_RECURSIVE)) {
 333                         /* We can't wrap it: We need a recursive lock */
 334                         _original_lock_fns.free(lock_, locktype);
 335                         return debug_lock_alloc(locktype);
 336                 }
 337                 lock = mm_malloc(sizeof(struct debug_lock));
 338                 if (!lock) {
 339                         _original_lock_fns.free(lock_, locktype);
 340                         return NULL;
 341                 }
 342                 lock->lock = lock_;
 343                 lock->locktype = locktype;
 344                 lock->count = 0;
 345                 lock->held_by = 0;
 346                 return lock;
 347         } else if (enable_locks && ! _evthread_lock_debugging_enabled) {
 348                 /* Case 3: allocate a regular lock */
 349                 EVUTIL_ASSERT(lock_ == NULL);
 350                 return _evthread_lock_fns.alloc(locktype);
 351         } else {
 352                 /* Case 4: Fill in a debug lock with a real lock */
 353                 struct debug_lock *lock = lock_;
 354                 EVUTIL_ASSERT(enable_locks &&
 355                               _evthread_lock_debugging_enabled);
 356                 EVUTIL_ASSERT(lock->locktype == locktype);
 357                 EVUTIL_ASSERT(lock->lock == NULL);
 358                 lock->lock = _original_lock_fns.alloc(
 359                         locktype|EVTHREAD_LOCKTYPE_RECURSIVE);
 360                 if (!lock->lock) {
 361                         lock->count = -200;
 362                         mm_free(lock);
 363                         return NULL;
 364                 }
 365                 return lock;
 366         }
 367 }
 368
 369
 370 #ifndef EVTHREAD_EXPOSE_STRUCTS
 371 unsigned long
 372 _evthreadimpl_get_id()
 373 {
 374         return _evthread_id_fn ? _evthread_id_fn() : 1;
 375 }
 376 void *
 377 _evthreadimpl_lock_alloc(unsigned locktype)
 378 {
 379         return _evthread_lock_fns.alloc ?
 380             _evthread_lock_fns.alloc(locktype) : NULL;
 381 }
 382 void
 383 _evthreadimpl_lock_free(void *lock, unsigned locktype)
 384 {
 385         if (_evthread_lock_fns.free)
 386                 _evthread_lock_fns.free(lock, locktype);
 387 }
 388 int
 389 _evthreadimpl_lock_lock(unsigned mode, void *lock)
 390 {
 391         if (_evthread_lock_fns.lock)
 392                 return _evthread_lock_fns.lock(mode, lock);
 393         else
 394                 return 0;
 395 }
 396 int
 397 _evthreadimpl_lock_unlock(unsigned mode, void *lock)
 398 {
 399         if (_evthread_lock_fns.unlock)
 400                 return _evthread_lock_fns.unlock(mode, lock);
 401         else
 402                 return 0;
 403 }
 404 void *
 405 _evthreadimpl_cond_alloc(unsigned condtype)
 406 {
 407         return _evthread_cond_fns.alloc_condition ?
 408             _evthread_cond_fns.alloc_condition(condtype) : NULL;
 409 }
 410 void
 411 _evthreadimpl_cond_free(void *cond)
 412 {
 413         if (_evthread_cond_fns.free_condition)
 414                 _evthread_cond_fns.free_condition(cond);
 415 }
 416 int
 417 _evthreadimpl_cond_signal(void *cond, int broadcast)
 418 {
 419         if (_evthread_cond_fns.signal_condition)
 420                 return _evthread_cond_fns.signal_condition(cond, broadcast);
 421         else
 422                 return 0;
 423 }
 424 int
 425 _evthreadimpl_cond_wait(void *cond, void *lock, const struct timeval *tv)
 426 {
 427         if (_evthread_cond_fns.wait_condition)
 428                 return _evthread_cond_fns.wait_condition(cond, lock, tv);
 429         else
 430                 return 0;
 431 }
 432 int
 433 _evthreadimpl_is_lock_debugging_enabled(void)
 434 {
 435         return _evthread_lock_debugging_enabled;
 436 }
 437
 438 int
 439 _evthreadimpl_locking_enabled(void)
 440 {
 441         return _evthread_lock_fns.lock != NULL;
 442 }
 443 #endif
 444
 445 #endif