mono/utils/mono-threads-coop.c

   1 /**
   2  * \file
   3  * Coop threading
   4  *
   5  * Author:
   6  *      Rodrigo Kumpera (kumpera@gmail.com)
   7  *
   8  * Copyright 2015 Xamarin, Inc (http://www.xamarin.com)
   9  * Licensed under the MIT license. See LICENSE file in the project root for full license information.
  10  */
  11
  12 #include <config.h>
  13
  14 /* enable pthread extensions */
  15 #ifdef TARGET_MACH
  16 #define _DARWIN_C_SOURCE
  17 #endif
  18
  19 #include <mono/utils/mono-compiler.h>
  20 #include <mono/utils/mono-threads.h>
  21 #include <mono/utils/mono-tls.h>
  22 #include <mono/utils/hazard-pointer.h>
  23 #include <mono/utils/mono-memory-model.h>
  24 #include <mono/utils/mono-mmap.h>
  25 #include <mono/utils/atomic.h>
  26 #include <mono/utils/mono-time.h>
  27 #include <mono/utils/mono-counters.h>
  28 #include <mono/utils/mono-threads-coop.h>
  29 #include <mono/utils/mono-threads-api.h>
  30 #include <mono/utils/checked-build.h>
  31 #include <mono/utils/mono-threads-debug.h>
  32
  33 #ifdef TARGET_OSX
  34 #include <mono/utils/mach-support.h>
  35 #endif
  36
  37 #ifdef _MSC_VER
  38 // TODO: Find MSVC replacement for __builtin_unwind_init
  39 #define SAVE_REGS_ON_STACK g_assert_not_reached ();
  40 #elif defined (HOST_WASM)
  41 //TODO: figure out wasm stack scanning
  42 #define SAVE_REGS_ON_STACK do {} while (0)
  43 #else
  44 #define SAVE_REGS_ON_STACK __builtin_unwind_init ();
  45 #endif
  46
  47 volatile size_t mono_polling_required;
  48
  49 // FIXME: This would be more efficient if instead of instantiating the stack it just pushed a simple depth counter up and down,
  50 // perhaps with a per-thread cookie in the high bits.
  51 #ifdef ENABLE_CHECKED_BUILD_GC
  52
  53 // Maintains a single per-thread stack of ints, used to ensure nesting is not violated
  54 static MonoNativeTlsKey coop_reset_count_stack_key;
  55
  56 static void
  57 coop_tls_push (gpointer cookie)
  58 {
  59         GArray *stack;
  60
  61         stack = mono_native_tls_get_value (coop_reset_count_stack_key);
  62         if (!stack) {
  63                 stack = g_array_new (FALSE, FALSE, sizeof(gpointer));
  64                 mono_native_tls_set_value (coop_reset_count_stack_key, stack);
  65         }
  66
  67         g_array_append_val (stack, cookie);
  68 }
  69
  70 static void
  71 coop_tls_pop (gpointer received_cookie)
  72 {
  73         GArray *stack;
  74         gpointer expected_cookie;
  75
  76         stack = mono_native_tls_get_value (coop_reset_count_stack_key);
  77         if (!stack || 0 == stack->len)
  78                 mono_fatal_with_history ("Received cookie %p but found no stack at all\n", received_cookie);
  79
  80         expected_cookie = g_array_index (stack, gpointer, stack->len - 1);
  81         stack->len --;
  82
  83         if (0 == stack->len) {
  84                 g_array_free (stack,TRUE);
  85                 mono_native_tls_set_value (coop_reset_count_stack_key, NULL);
  86         }
  87
  88         if (expected_cookie != received_cookie)
  89                 mono_fatal_with_history ("Received cookie %p but expected %p\n", received_cookie, expected_cookie);
  90 }
  91
  92 #endif
  93
  94 static void
  95 check_info (MonoThreadInfo *info, const gchar *action, const gchar *state)
  96 {
  97         if (!info)
  98                 g_error ("Cannot %s GC %s region if the thread is not attached", action, state);
  99         if (!mono_thread_info_is_current (info))
 100                 g_error ("[%p] Cannot %s GC %s region on a different thread", mono_thread_info_get_tid (info), action, state);
 101         if (!mono_thread_info_is_live (info))
 102                 g_error ("[%p] Cannot %s GC %s region if the thread is not live", mono_thread_info_get_tid (info), action, state);
 103 }
 104
 105 static int coop_reset_blocking_count;
 106 static int coop_try_blocking_count;
 107 static int coop_do_blocking_count;
 108 static int coop_do_polling_count;
 109 static int coop_save_count;
 110
 111 static void
 112 mono_threads_state_poll_with_info (MonoThreadInfo *info);
 113
 114 void
 115 mono_threads_state_poll (void)
 116 {
 117         mono_threads_state_poll_with_info (mono_thread_info_current_unchecked ());
 118 }
 119
 120 static void
 121 mono_threads_state_poll_with_info (MonoThreadInfo *info)
 122 {
 123         g_assert (mono_threads_is_blocking_transition_enabled ());
 124
 125         ++coop_do_polling_count;
 126
 127         if (!info)
 128                 return;
 129
 130         THREADS_SUSPEND_DEBUG ("FINISH SELF SUSPEND OF %p\n", mono_thread_info_get_tid (info));
 131
 132         /* Fast check for pending suspend requests */
 133         if (!(info->thread_state & (STATE_ASYNC_SUSPEND_REQUESTED | STATE_SELF_SUSPEND_REQUESTED)))
 134                 return;
 135
 136         ++coop_save_count;
 137         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 138
 139         /* commit the saved state and notify others if needed */
 140         switch (mono_threads_transition_state_poll (info)) {
 141         case SelfSuspendResumed:
 142                 break;
 143         case SelfSuspendWait:
 144                 mono_thread_info_wait_for_resume (info);
 145                 break;
 146         case SelfSuspendNotifyAndWait:
 147                 mono_threads_notify_initiator_of_suspend (info);
 148                 mono_thread_info_wait_for_resume (info);
 149                 break;
 150         }
 151
 152         if (info->async_target) {
 153                 info->async_target (info->user_data);
 154                 info->async_target = NULL;
 155                 info->user_data = NULL;
 156         }
 157 }
 158
 159 static volatile gpointer* dummy_global;
 160
 161 static MONO_NEVER_INLINE
 162 void*
 163 return_stack_ptr (gpointer *i)
 164 {
 165         dummy_global = i;
 166         return i;
 167 }
 168
 169 static void
 170 copy_stack_data (MonoThreadInfo *info, gpointer *stackdata_begin)
 171 {
 172         MonoThreadUnwindState *state;
 173         int stackdata_size;
 174         gpointer dummy;
 175         void* stackdata_end = return_stack_ptr (&dummy);
 176
 177         SAVE_REGS_ON_STACK;
 178
 179         state = &info->thread_saved_state [SELF_SUSPEND_STATE_INDEX];
 180
 181         stackdata_size = (char*)stackdata_begin - (char*)stackdata_end;
 182
 183         if (((gsize) stackdata_begin & (SIZEOF_VOID_P - 1)) != 0)
 184                 g_error ("stackdata_begin (%p) must be %d-byte aligned", stackdata_begin, SIZEOF_VOID_P);
 185         if (((gsize) stackdata_end & (SIZEOF_VOID_P - 1)) != 0)
 186                 g_error ("stackdata_end (%p) must be %d-byte aligned", stackdata_end, SIZEOF_VOID_P);
 187
 188         if (stackdata_size <= 0)
 189                 g_error ("stackdata_size = %d, but must be > 0, stackdata_begin = %p, stackdata_end = %p", stackdata_size, stackdata_begin, stackdata_end);
 190
 191         g_byte_array_set_size (info->stackdata, stackdata_size);
 192         state->gc_stackdata = info->stackdata->data;
 193         memcpy (state->gc_stackdata, stackdata_end, stackdata_size);
 194
 195         state->gc_stackdata_size = stackdata_size;
 196 }
 197
 198 static gpointer
 199 mono_threads_enter_gc_safe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata);
 200
 201 gpointer
 202 mono_threads_enter_gc_safe_region (gpointer *stackdata)
 203 {
 204         return mono_threads_enter_gc_safe_region_with_info (mono_thread_info_current_unchecked (), stackdata);
 205 }
 206
 207 gpointer
 208 mono_threads_enter_gc_safe_region_with_info (MonoThreadInfo *info, gpointer *stackdata)
 209 {
 210         gpointer cookie;
 211
 212         if (!mono_threads_is_blocking_transition_enabled ())
 213                 return NULL;
 214
 215         cookie = mono_threads_enter_gc_safe_region_unbalanced_with_info (info, stackdata);
 216
 217 #ifdef ENABLE_CHECKED_BUILD_GC
 218         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 219                 coop_tls_push (cookie);
 220 #endif
 221
 222         return cookie;
 223 }
 224
 225 gpointer
 226 mono_threads_enter_gc_safe_region_unbalanced (gpointer *stackdata)
 227 {
 228         return mono_threads_enter_gc_safe_region_unbalanced_with_info (mono_thread_info_current_unchecked (), stackdata);
 229 }
 230
 231 static gpointer
 232 mono_threads_enter_gc_safe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata)
 233 {
 234         if (!mono_threads_is_blocking_transition_enabled ())
 235                 return NULL;
 236
 237         ++coop_do_blocking_count;
 238
 239         check_info (info, "enter", "safe");
 240
 241         copy_stack_data (info, stackdata);
 242
 243 retry:
 244         ++coop_save_count;
 245         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 246
 247         switch (mono_threads_transition_do_blocking (info)) {
 248         case DoBlockingContinue:
 249                 break;
 250         case DoBlockingPollAndRetry:
 251                 mono_threads_state_poll_with_info (info);
 252                 goto retry;
 253         }
 254
 255         return info;
 256 }
 257
 258 void
 259 mono_threads_exit_gc_safe_region (gpointer cookie, gpointer *stackdata)
 260 {
 261         if (!mono_threads_is_blocking_transition_enabled ())
 262                 return;
 263
 264 #ifdef ENABLE_CHECKED_BUILD_GC
 265         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 266                 coop_tls_pop (cookie);
 267 #endif
 268
 269         mono_threads_exit_gc_safe_region_unbalanced (cookie, stackdata);
 270 }
 271
 272 void
 273 mono_threads_exit_gc_safe_region_unbalanced (gpointer cookie, gpointer *stackdata)
 274 {
 275         MonoThreadInfo *info;
 276
 277         if (!mono_threads_is_blocking_transition_enabled ())
 278                 return;
 279
 280         info = (MonoThreadInfo *)cookie;
 281
 282         check_info (info, "exit", "safe");
 283
 284         switch (mono_threads_transition_done_blocking (info)) {
 285         case DoneBlockingOk:
 286                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 287                 break;
 288         case DoneBlockingWait:
 289                 THREADS_SUSPEND_DEBUG ("state polling done, notifying of resume\n");
 290                 mono_thread_info_wait_for_resume (info);
 291                 break;
 292         default:
 293                 g_error ("Unknown thread state");
 294         }
 295
 296         if (info->async_target) {
 297                 info->async_target (info->user_data);
 298                 info->async_target = NULL;
 299                 info->user_data = NULL;
 300         }
 301 }
 302
 303 void
 304 mono_threads_assert_gc_safe_region (void)
 305 {
 306         MONO_REQ_GC_SAFE_MODE;
 307 }
 308
 309 gpointer
 310 mono_threads_enter_gc_unsafe_region (gpointer *stackdata)
 311 {
 312         return mono_threads_enter_gc_unsafe_region_with_info (mono_thread_info_current_unchecked (), stackdata);
 313 }
 314
 315 gpointer
 316 mono_threads_enter_gc_unsafe_region_with_info (THREAD_INFO_TYPE *info, gpointer *stackdata)
 317 {
 318         gpointer cookie;
 319
 320         if (!mono_threads_is_blocking_transition_enabled ())
 321                 return NULL;
 322
 323         cookie = mono_threads_enter_gc_unsafe_region_unbalanced_with_info (info, stackdata);
 324
 325 #ifdef ENABLE_CHECKED_BUILD_GC
 326         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 327                 coop_tls_push (cookie);
 328 #endif
 329
 330         return cookie;
 331 }
 332
 333 gpointer
 334 mono_threads_enter_gc_unsafe_region_unbalanced (gpointer *stackdata)
 335 {
 336         return mono_threads_enter_gc_unsafe_region_unbalanced_with_info (mono_thread_info_current_unchecked (), stackdata);
 337 }
 338
 339 gpointer
 340 mono_threads_enter_gc_unsafe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata)
 341 {
 342         if (!mono_threads_is_blocking_transition_enabled ())
 343                 return NULL;
 344
 345         ++coop_reset_blocking_count;
 346
 347         check_info (info, "enter", "unsafe");
 348
 349         copy_stack_data (info, stackdata);
 350
 351         switch (mono_threads_transition_abort_blocking (info)) {
 352         case AbortBlockingIgnore:
 353                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 354                 return NULL;
 355         case AbortBlockingIgnoreAndPoll:
 356                 mono_threads_state_poll_with_info (info);
 357                 return NULL;
 358         case AbortBlockingOk:
 359                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 360                 break;
 361         case AbortBlockingWait:
 362                 mono_thread_info_wait_for_resume (info);
 363                 break;
 364         default:
 365                 g_error ("Unknown thread state");
 366         }
 367
 368         if (info->async_target) {
 369                 info->async_target (info->user_data);
 370                 info->async_target = NULL;
 371                 info->user_data = NULL;
 372         }
 373
 374         return info;
 375 }
 376
 377 gpointer
 378 mono_threads_enter_gc_unsafe_region_cookie (void)
 379 {
 380         MonoThreadInfo *info;
 381
 382         g_assert (mono_threads_is_blocking_transition_enabled ());
 383
 384         info = mono_thread_info_current_unchecked ();
 385
 386         check_info (info, "enter (cookie)", "unsafe");
 387
 388 #ifdef ENABLE_CHECKED_BUILD_GC
 389         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 390                 coop_tls_push (info);
 391 #endif
 392
 393         return info;
 394 }
 395
 396 void
 397 mono_threads_exit_gc_unsafe_region (gpointer cookie, gpointer *stackdata)
 398 {
 399         if (!mono_threads_is_blocking_transition_enabled ())
 400                 return;
 401
 402 #ifdef ENABLE_CHECKED_BUILD_GC
 403         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 404                 coop_tls_pop (cookie);
 405 #endif
 406
 407         mono_threads_exit_gc_unsafe_region_unbalanced (cookie, stackdata);
 408 }
 409
 410 void
 411 mono_threads_exit_gc_unsafe_region_unbalanced (gpointer cookie, gpointer *stackdata)
 412 {
 413         if (!mono_threads_is_blocking_transition_enabled ())
 414                 return;
 415
 416         if (!cookie)
 417                 return;
 418
 419         mono_threads_enter_gc_safe_region_unbalanced (stackdata);
 420 }
 421
 422 void
 423 mono_threads_assert_gc_unsafe_region (void)
 424 {
 425         MONO_REQ_GC_UNSAFE_MODE;
 426 }
 427
 428 gboolean
 429 mono_threads_is_coop_enabled (void)
 430 {
 431 #if defined(USE_COOP_GC)
 432         return TRUE;
 433 #else
 434         static int is_coop_enabled = -1;
 435         if (G_UNLIKELY (is_coop_enabled == -1))
 436                 is_coop_enabled = g_hasenv ("MONO_ENABLE_COOP") ? 1 : 0;
 437         return is_coop_enabled == 1;
 438 #endif
 439 }
 440
 441 gboolean
 442 mono_threads_is_blocking_transition_enabled (void)
 443 {
 444 #if defined(USE_COOP_GC)
 445         return TRUE;
 446 #else
 447         static int is_blocking_transition_enabled = -1;
 448         if (G_UNLIKELY (is_blocking_transition_enabled == -1))
 449                 is_blocking_transition_enabled = (g_hasenv ("MONO_ENABLE_COOP") || g_hasenv ("MONO_ENABLE_BLOCKING_TRANSITION")) ? 1 : 0;
 450         return is_blocking_transition_enabled == 1;
 451 #endif
 452 }
 453
 454
 455 void
 456 mono_threads_coop_init (void)
 457 {
 458         if (!mono_threads_is_coop_enabled () && !mono_threads_is_blocking_transition_enabled ())
 459                 return;
 460
 461         mono_counters_register ("Coop Reset Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_reset_blocking_count);
 462         mono_counters_register ("Coop Try Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_try_blocking_count);
 463         mono_counters_register ("Coop Do Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_blocking_count);
 464         mono_counters_register ("Coop Do Polling", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_polling_count);
 465         mono_counters_register ("Coop Save Count", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_save_count);
 466         //See the above for what's wrong here.
 467
 468 #ifdef ENABLE_CHECKED_BUILD_GC
 469         mono_native_tls_alloc (&coop_reset_count_stack_key, NULL);
 470 #endif
 471 }
 472
 473 void
 474 mono_threads_coop_begin_global_suspend (void)
 475 {
 476         if (mono_threads_is_coop_enabled ())
 477                 mono_polling_required = 1;
 478 }
 479
 480 void
 481 mono_threads_coop_end_global_suspend (void)
 482 {
 483         if (mono_threads_is_coop_enabled ())
 484                 mono_polling_required = 0;
 485 }