mono/utils/mono-threads-coop.c

   1  /*
   2  * mono-threads.c: Coop threading
   3  *
   4  * Author:
   5  *      Rodrigo Kumpera (kumpera@gmail.com)
   6  *
   7  * Copyright 2015 Xamarin, Inc (http://www.xamarin.com)
   8  * Licensed under the MIT license. See LICENSE file in the project root for full license information.
   9  */
  10
  11 #include <config.h>
  12
  13 /* enable pthread extensions */
  14 #ifdef TARGET_MACH
  15 #define _DARWIN_C_SOURCE
  16 #endif
  17
  18 #include <mono/utils/mono-compiler.h>
  19 #include <mono/utils/mono-threads.h>
  20 #include <mono/utils/mono-tls.h>
  21 #include <mono/utils/hazard-pointer.h>
  22 #include <mono/utils/mono-memory-model.h>
  23 #include <mono/utils/mono-mmap.h>
  24 #include <mono/utils/atomic.h>
  25 #include <mono/utils/mono-time.h>
  26 #include <mono/utils/mono-counters.h>
  27 #include <mono/utils/mono-threads-coop.h>
  28 #include <mono/utils/mono-threads-api.h>
  29 #include <mono/utils/checked-build.h>
  30
  31 #ifdef TARGET_OSX
  32 #include <mono/utils/mach-support.h>
  33 #endif
  34
  35 #ifdef _MSC_VER
  36 // TODO: Find MSVC replacement for __builtin_unwind_init
  37 #define SAVE_REGS_ON_STACK g_assert_not_reached ();
  38 #else
  39 #define SAVE_REGS_ON_STACK __builtin_unwind_init ();
  40 #endif
  41
  42 volatile size_t mono_polling_required;
  43
  44 // FIXME: This would be more efficient if instead of instantiating the stack it just pushed a simple depth counter up and down,
  45 // perhaps with a per-thread cookie in the high bits.
  46 #ifdef ENABLE_CHECKED_BUILD_GC
  47
  48 // Maintains a single per-thread stack of ints, used to ensure nesting is not violated
  49 static MonoNativeTlsKey coop_reset_count_stack_key;
  50
  51 static void
  52 coop_tls_push (gpointer cookie)
  53 {
  54         GArray *stack;
  55
  56         stack = mono_native_tls_get_value (coop_reset_count_stack_key);
  57         if (!stack) {
  58                 stack = g_array_new (FALSE, FALSE, sizeof(gpointer));
  59                 mono_native_tls_set_value (coop_reset_count_stack_key, stack);
  60         }
  61
  62         g_array_append_val (stack, cookie);
  63 }
  64
  65 static void
  66 coop_tls_pop (gpointer received_cookie)
  67 {
  68         GArray *stack;
  69         gpointer expected_cookie;
  70
  71         stack = mono_native_tls_get_value (coop_reset_count_stack_key);
  72         if (!stack || 0 == stack->len)
  73                 mono_fatal_with_history ("Received cookie %p but found no stack at all, %x\n", received_cookie);
  74
  75         expected_cookie = g_array_index (stack, gpointer, stack->len - 1);
  76         stack->len --;
  77
  78         if (0 == stack->len) {
  79                 g_array_free (stack,TRUE);
  80                 mono_native_tls_set_value (coop_reset_count_stack_key, NULL);
  81         }
  82
  83         if (expected_cookie != received_cookie)
  84                 mono_fatal_with_history ("Received cookie %p but expected %p\n", received_cookie, expected_cookie);
  85 }
  86
  87 #endif
  88
  89 static int coop_reset_blocking_count;
  90 static int coop_try_blocking_count;
  91 static int coop_do_blocking_count;
  92 static int coop_do_polling_count;
  93 static int coop_save_count;
  94
  95 void
  96 mono_threads_state_poll (void)
  97 {
  98         MonoThreadInfo *info;
  99
 100         g_assert (mono_threads_is_coop_enabled ());
 101
 102         ++coop_do_polling_count;
 103
 104         info = mono_thread_info_current_unchecked ();
 105         if (!info)
 106                 return;
 107         THREADS_SUSPEND_DEBUG ("FINISH SELF SUSPEND OF %p\n", mono_thread_info_get_tid (info));
 108
 109         /* Fast check for pending suspend requests */
 110         if (!(info->thread_state & (STATE_ASYNC_SUSPEND_REQUESTED | STATE_SELF_SUSPEND_REQUESTED)))
 111                 return;
 112
 113         ++coop_save_count;
 114         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 115
 116         /* commit the saved state and notify others if needed */
 117         switch (mono_threads_transition_state_poll (info)) {
 118         case SelfSuspendResumed:
 119                 return;
 120         case SelfSuspendWait:
 121                 mono_thread_info_wait_for_resume (info);
 122                 break;
 123         case SelfSuspendNotifyAndWait:
 124                 mono_threads_notify_initiator_of_suspend (info);
 125                 mono_thread_info_wait_for_resume (info);
 126                 break;
 127         }
 128 }
 129
 130 static void *
 131 return_stack_ptr ()
 132 {
 133         gpointer i;
 134         return &i;
 135 }
 136
 137 static void
 138 copy_stack_data (MonoThreadInfo *info, gpointer *stackdata_begin)
 139 {
 140         MonoThreadUnwindState *state;
 141         int stackdata_size;
 142         void* stackdata_end = return_stack_ptr ();
 143
 144         SAVE_REGS_ON_STACK;
 145
 146         state = &info->thread_saved_state [SELF_SUSPEND_STATE_INDEX];
 147
 148         stackdata_size = (char*)stackdata_begin - (char*)stackdata_end;
 149
 150         if (((gsize) stackdata_begin & (SIZEOF_VOID_P - 1)) != 0)
 151                 g_error ("stackdata_begin (%p) must be %d-byte aligned", stackdata_begin, SIZEOF_VOID_P);
 152         if (((gsize) stackdata_end & (SIZEOF_VOID_P - 1)) != 0)
 153                 g_error ("stackdata_end (%p) must be %d-byte aligned", stackdata_end, SIZEOF_VOID_P);
 154
 155         if (stackdata_size <= 0)
 156                 g_error ("stackdata_size = %d, but must be > 0, stackdata_begin = %p, stackdata_end = %p", stackdata_size, stackdata_begin, stackdata_end);
 157
 158         g_byte_array_set_size (info->stackdata, stackdata_size);
 159         state->gc_stackdata = info->stackdata->data;
 160         memcpy (state->gc_stackdata, stackdata_end, stackdata_size);
 161
 162         state->gc_stackdata_size = stackdata_size;
 163 }
 164
 165 gpointer
 166 mono_threads_prepare_blocking (gpointer *stackdata)
 167 {
 168         gpointer cookie;
 169
 170         if (!mono_threads_is_coop_enabled ())
 171                 return NULL;
 172
 173         cookie = mono_threads_prepare_blocking_unbalanced (stackdata);
 174
 175 #ifdef ENABLE_CHECKED_BUILD_GC
 176         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 177                 coop_tls_push (cookie);
 178 #endif
 179
 180         return cookie;
 181 }
 182
 183 gpointer
 184 mono_threads_prepare_blocking_unbalanced (gpointer *stackdata)
 185 {
 186         MonoThreadInfo *info;
 187
 188         if (!mono_threads_is_coop_enabled ())
 189                 return NULL;
 190
 191         ++coop_do_blocking_count;
 192
 193         info = mono_thread_info_current_unchecked ();
 194         /* If the thread is not attached, it doesn't make sense prepare for suspend. */
 195         if (!info || !mono_thread_info_is_live (info)) {
 196                 THREADS_SUSPEND_DEBUG ("PREPARE-BLOCKING failed %p\n", info ? mono_thread_info_get_tid (info) : NULL);
 197                 return NULL;
 198         }
 199
 200         copy_stack_data (info, stackdata);
 201
 202 retry:
 203         ++coop_save_count;
 204         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 205
 206         switch (mono_threads_transition_do_blocking (info)) {
 207         case DoBlockingContinue:
 208                 break;
 209         case DoBlockingPollAndRetry:
 210                 mono_threads_state_poll ();
 211                 goto retry;
 212         }
 213
 214         return info;
 215 }
 216
 217 void
 218 mono_threads_finish_blocking (gpointer cookie, gpointer *stackdata)
 219 {
 220         if (!mono_threads_is_coop_enabled ())
 221                 return;
 222
 223 #ifdef ENABLE_CHECKED_BUILD_GC
 224         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 225                 coop_tls_pop (cookie);
 226 #endif
 227
 228         mono_threads_finish_blocking_unbalanced (cookie, stackdata);
 229 }
 230
 231 void
 232 mono_threads_finish_blocking_unbalanced (gpointer cookie, gpointer *stackdata)
 233 {
 234         static gboolean warned_about_bad_transition;
 235         MonoThreadInfo *info;
 236
 237         if (!mono_threads_is_coop_enabled ())
 238                 return;
 239
 240         info = (MonoThreadInfo *)cookie;
 241         if (!info)
 242                 return;
 243
 244         g_assert (info == mono_thread_info_current_unchecked ());
 245
 246         switch (mono_threads_transition_done_blocking (info)) {
 247         case DoneBlockingAborted:
 248                 if (!warned_about_bad_transition) {
 249                         warned_about_bad_transition = TRUE;
 250                         g_warning ("[%p] Blocking call ended in running state for, this might lead to unbound GC pauses.", mono_thread_info_get_tid (info));
 251                 }
 252                 mono_threads_state_poll ();
 253                 break;
 254         case DoneBlockingOk:
 255                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 256                 break;
 257         case DoneBlockingWait:
 258                 THREADS_SUSPEND_DEBUG ("state polling done, notifying of resume\n");
 259                 mono_thread_info_wait_for_resume (info);
 260                 break;
 261         default:
 262                 g_error ("Unknown thread state");
 263         }
 264 }
 265
 266 gpointer
 267 mono_threads_cookie_for_reset_blocking_start (MonoThreadInfo *info)
 268 {
 269         g_assert (mono_threads_is_coop_enabled ());
 270
 271 #ifdef ENABLE_CHECKED_BUILD_GC
 272         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 273                 coop_tls_push (info);
 274 #endif
 275
 276         return info;
 277 }
 278
 279 gpointer
 280 mono_threads_reset_blocking_start (gpointer *stackdata)
 281 {
 282         gpointer cookie;
 283
 284         if (!mono_threads_is_coop_enabled ())
 285                 return NULL;
 286
 287         cookie = mono_threads_reset_blocking_start_unbalanced (stackdata);
 288
 289 #ifdef ENABLE_CHECKED_BUILD_GC
 290         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 291                 coop_tls_push (cookie);
 292 #endif
 293
 294         return cookie;
 295 }
 296
 297 gpointer
 298 mono_threads_reset_blocking_start_unbalanced (gpointer *stackdata)
 299 {
 300         MonoThreadInfo *info;
 301
 302         if (!mono_threads_is_coop_enabled ())
 303                 return NULL;
 304
 305         ++coop_reset_blocking_count;
 306
 307         info = mono_thread_info_current_unchecked ();
 308
 309         /* If the thread is not attached, it doesn't make sense prepare for suspend. */
 310         if (!info || !mono_thread_info_is_live (info))
 311                 return NULL;
 312
 313         copy_stack_data (info, stackdata);
 314
 315         switch (mono_threads_transition_abort_blocking (info)) {
 316         case AbortBlockingIgnore:
 317                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 318                 return NULL;
 319         case AbortBlockingIgnoreAndPoll:
 320                 mono_threads_state_poll ();
 321                 return NULL;
 322         case AbortBlockingOk:
 323                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 324                 break;
 325         case AbortBlockingWait:
 326                 mono_thread_info_wait_for_resume (info);
 327                 break;
 328         default:
 329                 g_error ("Unknown thread state");
 330         }
 331
 332         return info;
 333 }
 334
 335 void
 336 mono_threads_reset_blocking_end (gpointer cookie, gpointer *stackdata)
 337 {
 338         if (!mono_threads_is_coop_enabled ())
 339                 return;
 340
 341 #ifdef ENABLE_CHECKED_BUILD_GC
 342         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 343                 coop_tls_pop (cookie);
 344 #endif
 345
 346         mono_threads_reset_blocking_end_unbalanced (cookie, stackdata);
 347 }
 348
 349 void
 350 mono_threads_reset_blocking_end_unbalanced (gpointer cookie, gpointer *stackdata)
 351 {
 352         if (!mono_threads_is_coop_enabled ())
 353                 return;
 354
 355         if (!cookie)
 356                 return;
 357
 358 #ifdef ENABLE_CHECKED_BUILD_GC
 359         if (!mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 360 #endif
 361         {
 362                 g_assert (((MonoThreadInfo *)cookie) == mono_thread_info_current_unchecked ());
 363         }
 364
 365         mono_threads_prepare_blocking_unbalanced (stackdata);
 366 }
 367
 368 void
 369 mono_threads_init_coop (void)
 370 {
 371         if (!mono_threads_is_coop_enabled ())
 372                 return;
 373
 374         mono_counters_register ("Coop Reset Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_reset_blocking_count);
 375         mono_counters_register ("Coop Try Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_try_blocking_count);
 376         mono_counters_register ("Coop Do Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_blocking_count);
 377         mono_counters_register ("Coop Do Polling", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_polling_count);
 378         mono_counters_register ("Coop Save Count", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_save_count);
 379         //See the above for what's wrong here.
 380
 381 #ifdef ENABLE_CHECKED_BUILD_GC
 382         mono_native_tls_alloc (&coop_reset_count_stack_key, NULL);
 383 #endif
 384 }
 385
 386 void
 387 mono_threads_coop_begin_global_suspend (void)
 388 {
 389         if (mono_threads_is_coop_enabled ())
 390                 mono_polling_required = 1;
 391 }
 392
 393 void
 394 mono_threads_coop_end_global_suspend (void)
 395 {
 396         if (mono_threads_is_coop_enabled ())
 397                 mono_polling_required = 0;
 398 }
 399
 400 gpointer
 401 mono_threads_enter_gc_unsafe_region (gpointer* stackdata)
 402 {
 403         if (!mono_threads_is_coop_enabled ())
 404                 return NULL;
 405
 406         return mono_threads_reset_blocking_start (stackdata);
 407 }
 408
 409 void
 410 mono_threads_exit_gc_unsafe_region (gpointer cookie, gpointer* stackdata)
 411 {
 412         if (!mono_threads_is_coop_enabled ())
 413                 return;
 414
 415         mono_threads_reset_blocking_end (cookie, stackdata);
 416 }
 417
 418 void
 419 mono_threads_assert_gc_unsafe_region (void)
 420 {
 421         MONO_REQ_GC_UNSAFE_MODE;
 422 }
 423
 424 gpointer
 425 mono_threads_enter_gc_safe_region (gpointer *stackdata)
 426 {
 427         if (!mono_threads_is_coop_enabled ())
 428                 return NULL;
 429
 430         return mono_threads_prepare_blocking (stackdata);
 431 }
 432
 433 void
 434 mono_threads_exit_gc_safe_region (gpointer cookie, gpointer *stackdata)
 435 {
 436         if (!mono_threads_is_coop_enabled ())
 437                 return;
 438
 439         mono_threads_finish_blocking (cookie, stackdata);
 440 }
 441
 442 void
 443 mono_threads_assert_gc_safe_region (void)
 444 {
 445         MONO_REQ_GC_SAFE_MODE;
 446 }