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