| 1 | /* Copyright (C) 2012, 2013, 2014 Free Software Foundation, Inc. |
| 2 | * |
| 3 | * This library is free software; you can redistribute it and/or |
| 4 | * modify it under the terms of the GNU Lesser General Public License |
| 5 | * as published by the Free Software Foundation; either version 3 of |
| 6 | * the License, or (at your option) any later version. |
| 7 | * |
| 8 | * This library is distributed in the hope that it will be useful, but |
| 9 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
| 10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 11 | * Lesser General Public License for more details. |
| 12 | * |
| 13 | * You should have received a copy of the GNU Lesser General Public |
| 14 | * License along with this library; if not, write to the Free Software |
| 15 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| 16 | * 02110-1301 USA |
| 17 | */ |
| 18 | |
| 19 | |
| 20 | \f |
| 21 | |
| 22 | #ifdef HAVE_CONFIG_H |
| 23 | # include <config.h> |
| 24 | #endif |
| 25 | |
| 26 | #include <unistd.h> |
| 27 | #include <fcntl.h> |
| 28 | |
| 29 | #include <full-write.h> |
| 30 | |
| 31 | #include "libguile/bdw-gc.h" |
| 32 | #include "libguile/_scm.h" |
| 33 | #include "libguile/finalizers.h" |
| 34 | #include "libguile/gc.h" |
| 35 | #include "libguile/threads.h" |
| 36 | |
| 37 | \f |
| 38 | |
| 39 | static int automatic_finalization_p = 1; |
| 40 | |
| 41 | static size_t finalization_count; |
| 42 | |
| 43 | |
| 44 | \f |
| 45 | |
| 46 | void |
| 47 | scm_i_set_finalizer (void *obj, scm_t_finalizer_proc proc, void *data) |
| 48 | { |
| 49 | GC_finalization_proc prev; |
| 50 | void *prev_data; |
| 51 | GC_REGISTER_FINALIZER_NO_ORDER (obj, proc, data, &prev, &prev_data); |
| 52 | } |
| 53 | |
| 54 | struct scm_t_chained_finalizer |
| 55 | { |
| 56 | int resuscitating_p; |
| 57 | scm_t_finalizer_proc proc; |
| 58 | void *data; |
| 59 | scm_t_finalizer_proc prev; |
| 60 | void *prev_data; |
| 61 | }; |
| 62 | |
| 63 | static void |
| 64 | chained_finalizer (void *obj, void *data) |
| 65 | { |
| 66 | struct scm_t_chained_finalizer *chained_data = data; |
| 67 | if (chained_data->resuscitating_p) |
| 68 | { |
| 69 | if (chained_data->prev) |
| 70 | scm_i_set_finalizer (obj, chained_data->prev, chained_data->prev_data); |
| 71 | chained_data->proc (obj, chained_data->data); |
| 72 | } |
| 73 | else |
| 74 | { |
| 75 | chained_data->proc (obj, chained_data->data); |
| 76 | if (chained_data->prev) |
| 77 | chained_data->prev (obj, chained_data->prev_data); |
| 78 | } |
| 79 | } |
| 80 | |
| 81 | void |
| 82 | scm_i_add_resuscitator (void *obj, scm_t_finalizer_proc proc, void *data) |
| 83 | { |
| 84 | struct scm_t_chained_finalizer *chained_data; |
| 85 | chained_data = scm_gc_malloc (sizeof (*chained_data), "chained finalizer"); |
| 86 | chained_data->resuscitating_p = 1; |
| 87 | chained_data->proc = proc; |
| 88 | chained_data->data = data; |
| 89 | GC_REGISTER_FINALIZER_NO_ORDER (obj, chained_finalizer, chained_data, |
| 90 | &chained_data->prev, |
| 91 | &chained_data->prev_data); |
| 92 | } |
| 93 | |
| 94 | static void |
| 95 | shuffle_resuscitators_to_front (struct scm_t_chained_finalizer *cd) |
| 96 | { |
| 97 | while (cd->prev == chained_finalizer) |
| 98 | { |
| 99 | struct scm_t_chained_finalizer *prev = cd->prev_data; |
| 100 | scm_t_finalizer_proc proc = cd->proc; |
| 101 | void *data = cd->data; |
| 102 | |
| 103 | if (!prev->resuscitating_p) |
| 104 | break; |
| 105 | |
| 106 | cd->resuscitating_p = 1; |
| 107 | cd->proc = prev->proc; |
| 108 | cd->data = prev->data; |
| 109 | |
| 110 | prev->resuscitating_p = 0; |
| 111 | prev->proc = proc; |
| 112 | prev->data = data; |
| 113 | |
| 114 | cd = prev; |
| 115 | } |
| 116 | } |
| 117 | |
| 118 | void |
| 119 | scm_i_add_finalizer (void *obj, scm_t_finalizer_proc proc, void *data) |
| 120 | { |
| 121 | struct scm_t_chained_finalizer *chained_data; |
| 122 | chained_data = scm_gc_malloc (sizeof (*chained_data), "chained finalizer"); |
| 123 | chained_data->resuscitating_p = 0; |
| 124 | chained_data->proc = proc; |
| 125 | chained_data->data = data; |
| 126 | GC_REGISTER_FINALIZER_NO_ORDER (obj, chained_finalizer, chained_data, |
| 127 | &chained_data->prev, |
| 128 | &chained_data->prev_data); |
| 129 | shuffle_resuscitators_to_front (chained_data); |
| 130 | } |
| 131 | |
| 132 | |
| 133 | \f |
| 134 | |
| 135 | static SCM finalizer_async_cell; |
| 136 | |
| 137 | static SCM |
| 138 | run_finalizers_async_thunk (void) |
| 139 | { |
| 140 | scm_run_finalizers (); |
| 141 | return SCM_UNSPECIFIED; |
| 142 | } |
| 143 | |
| 144 | |
| 145 | /* The function queue_finalizer_async is run by the GC when there are |
| 146 | * objects to finalize. It will enqueue an asynchronous call to |
| 147 | * GC_invoke_finalizers() at the next SCM_TICK in this thread. |
| 148 | */ |
| 149 | static void |
| 150 | queue_finalizer_async (void) |
| 151 | { |
| 152 | scm_i_thread *t = SCM_I_CURRENT_THREAD; |
| 153 | static scm_i_pthread_mutex_t lock = SCM_I_PTHREAD_MUTEX_INITIALIZER; |
| 154 | |
| 155 | scm_i_pthread_mutex_lock (&lock); |
| 156 | /* If t is NULL, that could be because we're allocating in |
| 157 | threads.c:guilify_self_1. In that case, rely on the |
| 158 | GC_invoke_finalizers call there after the thread spins up. */ |
| 159 | if (t && scm_is_false (SCM_CDR (finalizer_async_cell))) |
| 160 | { |
| 161 | SCM_SETCDR (finalizer_async_cell, t->active_asyncs); |
| 162 | t->active_asyncs = finalizer_async_cell; |
| 163 | t->pending_asyncs = 1; |
| 164 | } |
| 165 | scm_i_pthread_mutex_unlock (&lock); |
| 166 | } |
| 167 | |
| 168 | |
| 169 | \f |
| 170 | |
| 171 | #if SCM_USE_PTHREAD_THREADS |
| 172 | |
| 173 | static int finalization_pipe[2]; |
| 174 | static scm_i_pthread_mutex_t finalization_thread_lock = |
| 175 | SCM_I_PTHREAD_MUTEX_INITIALIZER; |
| 176 | static pthread_t finalization_thread; |
| 177 | static int finalization_thread_is_running = 0; |
| 178 | |
| 179 | static void |
| 180 | notify_finalizers_to_run (void) |
| 181 | { |
| 182 | char byte = 0; |
| 183 | full_write (finalization_pipe[1], &byte, 1); |
| 184 | } |
| 185 | |
| 186 | static void |
| 187 | notify_about_to_fork (void) |
| 188 | { |
| 189 | char byte = 1; |
| 190 | full_write (finalization_pipe[1], &byte, 1); |
| 191 | } |
| 192 | |
| 193 | struct finalization_pipe_data |
| 194 | { |
| 195 | char byte; |
| 196 | ssize_t n; |
| 197 | int err; |
| 198 | }; |
| 199 | |
| 200 | static void* |
| 201 | read_finalization_pipe_data (void *data) |
| 202 | { |
| 203 | struct finalization_pipe_data *fdata = data; |
| 204 | |
| 205 | fdata->n = read (finalization_pipe[0], &fdata->byte, 1); |
| 206 | fdata->err = errno; |
| 207 | |
| 208 | return NULL; |
| 209 | } |
| 210 | |
| 211 | static void* |
| 212 | finalization_thread_proc (void *unused) |
| 213 | { |
| 214 | while (1) |
| 215 | { |
| 216 | struct finalization_pipe_data data; |
| 217 | |
| 218 | scm_without_guile (read_finalization_pipe_data, &data); |
| 219 | |
| 220 | if (data.n <= 0 && data.err != EINTR) |
| 221 | { |
| 222 | perror ("error in finalization thread"); |
| 223 | return NULL; |
| 224 | } |
| 225 | |
| 226 | switch (data.byte) |
| 227 | { |
| 228 | case 0: |
| 229 | scm_run_finalizers (); |
| 230 | break; |
| 231 | case 1: |
| 232 | return NULL; |
| 233 | default: |
| 234 | abort (); |
| 235 | } |
| 236 | } |
| 237 | } |
| 238 | |
| 239 | static void* |
| 240 | run_finalization_thread (void *arg) |
| 241 | { |
| 242 | return scm_with_guile (finalization_thread_proc, arg); |
| 243 | } |
| 244 | |
| 245 | static void |
| 246 | start_finalization_thread (void) |
| 247 | { |
| 248 | scm_i_pthread_mutex_lock (&finalization_thread_lock); |
| 249 | if (!finalization_thread_is_running) |
| 250 | { |
| 251 | /* Use the raw pthread API and scm_with_guile, because we don't want |
| 252 | to block on any lock that scm_spawn_thread might want to take, |
| 253 | and we don't want to inherit the dynamic state (fluids) of the |
| 254 | caller. */ |
| 255 | if (pthread_create (&finalization_thread, NULL, |
| 256 | run_finalization_thread, NULL)) |
| 257 | perror ("error creating finalization thread"); |
| 258 | else |
| 259 | finalization_thread_is_running = 1; |
| 260 | } |
| 261 | scm_i_pthread_mutex_unlock (&finalization_thread_lock); |
| 262 | } |
| 263 | |
| 264 | static void |
| 265 | stop_finalization_thread (void) |
| 266 | { |
| 267 | scm_i_pthread_mutex_lock (&finalization_thread_lock); |
| 268 | if (finalization_thread_is_running) |
| 269 | { |
| 270 | notify_about_to_fork (); |
| 271 | if (pthread_join (finalization_thread, NULL)) |
| 272 | perror ("joining finalization thread"); |
| 273 | finalization_thread_is_running = 0; |
| 274 | } |
| 275 | scm_i_pthread_mutex_unlock (&finalization_thread_lock); |
| 276 | } |
| 277 | |
| 278 | static void |
| 279 | spawn_finalizer_thread (void) |
| 280 | { |
| 281 | GC_set_finalizer_notifier (notify_finalizers_to_run); |
| 282 | start_finalization_thread (); |
| 283 | } |
| 284 | |
| 285 | #endif /* SCM_USE_PTHREAD_THREADS */ |
| 286 | |
| 287 | |
| 288 | \f |
| 289 | |
| 290 | void |
| 291 | scm_i_finalizer_pre_fork (void) |
| 292 | { |
| 293 | #if SCM_USE_PTHREAD_THREADS |
| 294 | if (automatic_finalization_p) |
| 295 | { |
| 296 | stop_finalization_thread (); |
| 297 | GC_set_finalizer_notifier (spawn_finalizer_thread); |
| 298 | } |
| 299 | #endif |
| 300 | } |
| 301 | |
| 302 | |
| 303 | \f |
| 304 | |
| 305 | static void* |
| 306 | weak_pointer_ref (void *weak_pointer) |
| 307 | { |
| 308 | return *(void **) weak_pointer; |
| 309 | } |
| 310 | |
| 311 | static void |
| 312 | weak_gc_finalizer (void *ptr, void *data) |
| 313 | { |
| 314 | void **weak = ptr; |
| 315 | void *val; |
| 316 | void (*callback) (SCM) = weak[1]; |
| 317 | |
| 318 | val = GC_call_with_alloc_lock (weak_pointer_ref, &weak[0]); |
| 319 | |
| 320 | if (!val) |
| 321 | return; |
| 322 | |
| 323 | callback (SCM_PACK_POINTER (val)); |
| 324 | |
| 325 | scm_i_set_finalizer (ptr, weak_gc_finalizer, data); |
| 326 | } |
| 327 | |
| 328 | /* CALLBACK will be called on OBJ, as long as OBJ is accessible. It |
| 329 | will be called from a finalizer, which may be from an async or from |
| 330 | another thread. |
| 331 | |
| 332 | As an implementation detail, the way this works is that we allocate |
| 333 | a fresh pointer-less object holding two words. We know that this |
| 334 | object should get collected the next time GC is run, so we attach a |
| 335 | finalizer to it so that we get a callback after GC happens. |
| 336 | |
| 337 | The first word of the object holds a weak reference to OBJ, and the |
| 338 | second holds the callback pointer. When the callback is called, we |
| 339 | check if the weak reference on OBJ still holds. If it doesn't hold, |
| 340 | then OBJ is no longer accessible, and we're done. Otherwise we call |
| 341 | the callback and re-register a finalizer for our two-word GC object, |
| 342 | effectively resuscitating the object so that we will get a callback |
| 343 | on the next GC. |
| 344 | |
| 345 | We could use the scm_after_gc_hook, but using a finalizer has the |
| 346 | advantage of potentially running in another thread, decreasing pause |
| 347 | time. */ |
| 348 | void |
| 349 | scm_i_register_weak_gc_callback (SCM obj, void (*callback) (SCM)) |
| 350 | { |
| 351 | void **weak = GC_MALLOC_ATOMIC (sizeof (void*) * 2); |
| 352 | |
| 353 | weak[0] = SCM_UNPACK_POINTER (obj); |
| 354 | weak[1] = (void*)callback; |
| 355 | GC_GENERAL_REGISTER_DISAPPEARING_LINK (weak, SCM2PTR (obj)); |
| 356 | |
| 357 | scm_i_set_finalizer (weak, weak_gc_finalizer, NULL); |
| 358 | } |
| 359 | |
| 360 | |
| 361 | int |
| 362 | scm_set_automatic_finalization_enabled (int enabled_p) |
| 363 | { |
| 364 | int was_enabled_p = automatic_finalization_p; |
| 365 | |
| 366 | if (enabled_p == was_enabled_p) |
| 367 | return was_enabled_p; |
| 368 | |
| 369 | if (!scm_initialized_p) |
| 370 | { |
| 371 | automatic_finalization_p = enabled_p; |
| 372 | return was_enabled_p; |
| 373 | } |
| 374 | |
| 375 | if (enabled_p) |
| 376 | { |
| 377 | #if SCM_USE_PTHREAD_THREADS |
| 378 | if (pipe2 (finalization_pipe, O_CLOEXEC) != 0) |
| 379 | scm_syserror (NULL); |
| 380 | GC_set_finalizer_notifier (spawn_finalizer_thread); |
| 381 | #else |
| 382 | GC_set_finalizer_notifier (queue_finalizer_async); |
| 383 | #endif |
| 384 | } |
| 385 | else |
| 386 | { |
| 387 | GC_set_finalizer_notifier (0); |
| 388 | |
| 389 | #if SCM_USE_PTHREAD_THREADS |
| 390 | stop_finalization_thread (); |
| 391 | close (finalization_pipe[0]); |
| 392 | close (finalization_pipe[1]); |
| 393 | finalization_pipe[0] = -1; |
| 394 | finalization_pipe[1] = -1; |
| 395 | #endif |
| 396 | } |
| 397 | |
| 398 | automatic_finalization_p = enabled_p; |
| 399 | |
| 400 | return was_enabled_p; |
| 401 | } |
| 402 | |
| 403 | int |
| 404 | scm_run_finalizers (void) |
| 405 | { |
| 406 | int finalized = GC_invoke_finalizers (); |
| 407 | |
| 408 | finalization_count += finalized; |
| 409 | |
| 410 | return finalized; |
| 411 | } |
| 412 | |
| 413 | |
| 414 | \f |
| 415 | |
| 416 | void |
| 417 | scm_init_finalizers (void) |
| 418 | { |
| 419 | /* When the async is to run, the cdr of the pair gets set to the |
| 420 | asyncs queue of the current thread. */ |
| 421 | finalizer_async_cell = |
| 422 | scm_cons (scm_c_make_gsubr ("%run-finalizers", 0, 0, 0, |
| 423 | run_finalizers_async_thunk), |
| 424 | SCM_BOOL_F); |
| 425 | |
| 426 | if (automatic_finalization_p) |
| 427 | GC_set_finalizer_notifier (queue_finalizer_async); |
| 428 | } |
| 429 | |
| 430 | void |
| 431 | scm_init_finalizer_thread (void) |
| 432 | { |
| 433 | #if SCM_USE_PTHREAD_THREADS |
| 434 | if (automatic_finalization_p) |
| 435 | { |
| 436 | if (pipe2 (finalization_pipe, O_CLOEXEC) != 0) |
| 437 | scm_syserror (NULL); |
| 438 | GC_set_finalizer_notifier (spawn_finalizer_thread); |
| 439 | } |
| 440 | #endif |
| 441 | } |