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 void
  90 check_info (MonoThreadInfo *info, const gchar *action, const gchar *state)
  91 {
  92         if (!info)
  93                 g_error ("Cannot %s GC %s region if the thread is not attached", action, state);
  94         if (!mono_thread_info_is_current (info))
  95                 g_error ("[%p] Cannot %s GC %s region on a different thread", mono_thread_info_get_tid (info), action, state);
  96         if (!mono_thread_info_is_live (info))
  97                 g_error ("[%p] Cannot %s GC %s region if the thread is not live", mono_thread_info_get_tid (info), action, state);
  98 }
  99
 100 static int coop_reset_blocking_count;
 101 static int coop_try_blocking_count;
 102 static int coop_do_blocking_count;
 103 static int coop_do_polling_count;
 104 static int coop_save_count;
 105
 106 void
 107 mono_threads_state_poll (void)
 108 {
 109         MonoThreadInfo *info;
 110
 111         g_assert (mono_threads_is_coop_enabled ());
 112
 113         ++coop_do_polling_count;
 114
 115         info = mono_thread_info_current_unchecked ();
 116         if (!info)
 117                 return;
 118         THREADS_SUSPEND_DEBUG ("FINISH SELF SUSPEND OF %p\n", mono_thread_info_get_tid (info));
 119
 120         /* Fast check for pending suspend requests */
 121         if (!(info->thread_state & (STATE_ASYNC_SUSPEND_REQUESTED | STATE_SELF_SUSPEND_REQUESTED)))
 122                 return;
 123
 124         ++coop_save_count;
 125         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 126
 127         /* commit the saved state and notify others if needed */
 128         switch (mono_threads_transition_state_poll (info)) {
 129         case SelfSuspendResumed:
 130                 return;
 131         case SelfSuspendWait:
 132                 mono_thread_info_wait_for_resume (info);
 133                 break;
 134         case SelfSuspendNotifyAndWait:
 135                 mono_threads_notify_initiator_of_suspend (info);
 136                 mono_thread_info_wait_for_resume (info);
 137                 break;
 138         }
 139 }
 140
 141 static void *
 142 return_stack_ptr ()
 143 {
 144         gpointer i;
 145         return &i;
 146 }
 147
 148 static void
 149 copy_stack_data (MonoThreadInfo *info, gpointer *stackdata_begin)
 150 {
 151         MonoThreadUnwindState *state;
 152         int stackdata_size;
 153         void* stackdata_end = return_stack_ptr ();
 154
 155         SAVE_REGS_ON_STACK;
 156
 157         state = &info->thread_saved_state [SELF_SUSPEND_STATE_INDEX];
 158
 159         stackdata_size = (char*)stackdata_begin - (char*)stackdata_end;
 160
 161         if (((gsize) stackdata_begin & (SIZEOF_VOID_P - 1)) != 0)
 162                 g_error ("stackdata_begin (%p) must be %d-byte aligned", stackdata_begin, SIZEOF_VOID_P);
 163         if (((gsize) stackdata_end & (SIZEOF_VOID_P - 1)) != 0)
 164                 g_error ("stackdata_end (%p) must be %d-byte aligned", stackdata_end, SIZEOF_VOID_P);
 165
 166         if (stackdata_size <= 0)
 167                 g_error ("stackdata_size = %d, but must be > 0, stackdata_begin = %p, stackdata_end = %p", stackdata_size, stackdata_begin, stackdata_end);
 168
 169         g_byte_array_set_size (info->stackdata, stackdata_size);
 170         state->gc_stackdata = info->stackdata->data;
 171         memcpy (state->gc_stackdata, stackdata_end, stackdata_size);
 172
 173         state->gc_stackdata_size = stackdata_size;
 174 }
 175
 176 static gpointer
 177 mono_threads_enter_gc_safe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata);
 178
 179 gpointer
 180 mono_threads_enter_gc_safe_region (gpointer *stackdata)
 181 {
 182         return mono_threads_enter_gc_safe_region_with_info (mono_thread_info_current_unchecked (), stackdata);
 183 }
 184
 185 gpointer
 186 mono_threads_enter_gc_safe_region_with_info (MonoThreadInfo *info, gpointer *stackdata)
 187 {
 188         gpointer cookie;
 189
 190         if (!mono_threads_is_coop_enabled ())
 191                 return NULL;
 192
 193         cookie = mono_threads_enter_gc_safe_region_unbalanced_with_info (info, stackdata);
 194
 195 #ifdef ENABLE_CHECKED_BUILD_GC
 196         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 197                 coop_tls_push (cookie);
 198 #endif
 199
 200         return cookie;
 201 }
 202
 203 gpointer
 204 mono_threads_enter_gc_safe_region_unbalanced (gpointer *stackdata)
 205 {
 206         return mono_threads_enter_gc_safe_region_unbalanced_with_info (mono_thread_info_current_unchecked (), stackdata);
 207 }
 208
 209 static gpointer
 210 mono_threads_enter_gc_safe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata)
 211 {
 212         if (!mono_threads_is_coop_enabled ())
 213                 return NULL;
 214
 215         ++coop_do_blocking_count;
 216
 217         check_info (info, "enter", "safe");
 218
 219         copy_stack_data (info, stackdata);
 220
 221 retry:
 222         ++coop_save_count;
 223         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 224
 225         switch (mono_threads_transition_do_blocking (info)) {
 226         case DoBlockingContinue:
 227                 break;
 228         case DoBlockingPollAndRetry:
 229                 mono_threads_state_poll ();
 230                 goto retry;
 231         }
 232
 233         return info;
 234 }
 235
 236 void
 237 mono_threads_exit_gc_safe_region (gpointer cookie, gpointer *stackdata)
 238 {
 239         if (!mono_threads_is_coop_enabled ())
 240                 return;
 241
 242 #ifdef ENABLE_CHECKED_BUILD_GC
 243         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 244                 coop_tls_pop (cookie);
 245 #endif
 246
 247         mono_threads_exit_gc_safe_region_unbalanced (cookie, stackdata);
 248 }
 249
 250 void
 251 mono_threads_exit_gc_safe_region_unbalanced (gpointer cookie, gpointer *stackdata)
 252 {
 253         MonoThreadInfo *info;
 254
 255         if (!mono_threads_is_coop_enabled ())
 256                 return;
 257
 258         info = (MonoThreadInfo *)cookie;
 259
 260         check_info (info, "exit", "safe");
 261
 262         switch (mono_threads_transition_done_blocking (info)) {
 263         case DoneBlockingOk:
 264                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 265                 break;
 266         case DoneBlockingWait:
 267                 THREADS_SUSPEND_DEBUG ("state polling done, notifying of resume\n");
 268                 mono_thread_info_wait_for_resume (info);
 269                 break;
 270         default:
 271                 g_error ("Unknown thread state");
 272         }
 273 }
 274
 275 void
 276 mono_threads_assert_gc_safe_region (void)
 277 {
 278         MONO_REQ_GC_SAFE_MODE;
 279 }
 280
 281 gpointer
 282 mono_threads_enter_gc_unsafe_region (gpointer *stackdata)
 283 {
 284         return mono_threads_enter_gc_unsafe_region_with_info (mono_thread_info_current_unchecked (), stackdata);
 285 }
 286
 287 gpointer
 288 mono_threads_enter_gc_unsafe_region_with_info (THREAD_INFO_TYPE *info, gpointer *stackdata)
 289 {
 290         gpointer cookie;
 291
 292         if (!mono_threads_is_coop_enabled ())
 293                 return NULL;
 294
 295         cookie = mono_threads_enter_gc_unsafe_region_unbalanced_with_info (info, stackdata);
 296
 297 #ifdef ENABLE_CHECKED_BUILD_GC
 298         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 299                 coop_tls_push (cookie);
 300 #endif
 301
 302         return cookie;
 303 }
 304
 305 gpointer
 306 mono_threads_enter_gc_unsafe_region_unbalanced (gpointer *stackdata)
 307 {
 308         return mono_threads_enter_gc_unsafe_region_unbalanced_with_info (mono_thread_info_current_unchecked (), stackdata);
 309 }
 310
 311 gpointer
 312 mono_threads_enter_gc_unsafe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata)
 313 {
 314         if (!mono_threads_is_coop_enabled ())
 315                 return NULL;
 316
 317         ++coop_reset_blocking_count;
 318
 319         check_info (info, "enter", "unsafe");
 320
 321         copy_stack_data (info, stackdata);
 322
 323         switch (mono_threads_transition_abort_blocking (info)) {
 324         case AbortBlockingIgnore:
 325                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 326                 return NULL;
 327         case AbortBlockingIgnoreAndPoll:
 328                 mono_threads_state_poll ();
 329                 return NULL;
 330         case AbortBlockingOk:
 331                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 332                 break;
 333         case AbortBlockingWait:
 334                 mono_thread_info_wait_for_resume (info);
 335                 break;
 336         default:
 337                 g_error ("Unknown thread state");
 338         }
 339
 340         return info;
 341 }
 342
 343 gpointer
 344 mono_threads_enter_gc_unsafe_region_cookie (void)
 345 {
 346         MonoThreadInfo *info;
 347
 348         g_assert (mono_threads_is_coop_enabled ());
 349
 350         info = mono_thread_info_current_unchecked ();
 351
 352         check_info (info, "enter (cookie)", "unsafe");
 353
 354 #ifdef ENABLE_CHECKED_BUILD_GC
 355         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 356                 coop_tls_push (info);
 357 #endif
 358
 359         return info;
 360 }
 361
 362 void
 363 mono_threads_exit_gc_unsafe_region (gpointer cookie, gpointer *stackdata)
 364 {
 365         if (!mono_threads_is_coop_enabled ())
 366                 return;
 367
 368 #ifdef ENABLE_CHECKED_BUILD_GC
 369         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 370                 coop_tls_pop (cookie);
 371 #endif
 372
 373         mono_threads_exit_gc_unsafe_region_unbalanced (cookie, stackdata);
 374 }
 375
 376 void
 377 mono_threads_exit_gc_unsafe_region_unbalanced (gpointer cookie, gpointer *stackdata)
 378 {
 379         if (!mono_threads_is_coop_enabled ())
 380                 return;
 381
 382         if (!cookie)
 383                 return;
 384
 385 #ifdef ENABLE_CHECKED_BUILD_GC
 386         if (!mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 387 #endif
 388         {
 389                 g_assert (((MonoThreadInfo *)cookie) == mono_thread_info_current_unchecked ());
 390         }
 391
 392         mono_threads_enter_gc_safe_region_unbalanced (stackdata);
 393 }
 394
 395 void
 396 mono_threads_assert_gc_unsafe_region (void)
 397 {
 398         MONO_REQ_GC_UNSAFE_MODE;
 399 }
 400
 401 gboolean
 402 mono_threads_is_coop_enabled (void)
 403 {
 404 #if defined(USE_COOP_GC)
 405         return TRUE;
 406 #else
 407         static int is_coop_enabled = -1;
 408         if (G_UNLIKELY (is_coop_enabled == -1))
 409                 is_coop_enabled = g_getenv ("MONO_ENABLE_COOP") != NULL ? 1 : 0;
 410         return is_coop_enabled == 1;
 411 #endif
 412 }
 413
 414
 415 void
 416 mono_threads_init_coop (void)
 417 {
 418         if (!mono_threads_is_coop_enabled ())
 419                 return;
 420
 421         mono_counters_register ("Coop Reset Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_reset_blocking_count);
 422         mono_counters_register ("Coop Try Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_try_blocking_count);
 423         mono_counters_register ("Coop Do Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_blocking_count);
 424         mono_counters_register ("Coop Do Polling", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_polling_count);
 425         mono_counters_register ("Coop Save Count", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_save_count);
 426         //See the above for what's wrong here.
 427
 428 #ifdef ENABLE_CHECKED_BUILD_GC
 429         mono_native_tls_alloc (&coop_reset_count_stack_key, NULL);
 430 #endif
 431 }
 432
 433 void
 434 mono_threads_coop_begin_global_suspend (void)
 435 {
 436         if (mono_threads_is_coop_enabled ())
 437                 mono_polling_required = 1;
 438 }
 439
 440 void
 441 mono_threads_coop_end_global_suspend (void)
 442 {
 443         if (mono_threads_is_coop_enabled ())
 444                 mono_polling_required = 0;
 445 }