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 static void
 107 mono_threads_state_poll_with_info (MonoThreadInfo *info);
 108
 109 void
 110 mono_threads_state_poll (void)
 111 {
 112         mono_threads_state_poll_with_info (mono_thread_info_current_unchecked ());
 113 }
 114
 115 static void
 116 mono_threads_state_poll_with_info (MonoThreadInfo *info)
 117 {
 118         g_assert (mono_threads_is_coop_enabled ());
 119
 120         ++coop_do_polling_count;
 121
 122         if (!info)
 123                 return;
 124
 125         THREADS_SUSPEND_DEBUG ("FINISH SELF SUSPEND OF %p\n", mono_thread_info_get_tid (info));
 126
 127         /* Fast check for pending suspend requests */
 128         if (!(info->thread_state & (STATE_ASYNC_SUSPEND_REQUESTED | STATE_SELF_SUSPEND_REQUESTED)))
 129                 return;
 130
 131         ++coop_save_count;
 132         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 133
 134         /* commit the saved state and notify others if needed */
 135         switch (mono_threads_transition_state_poll (info)) {
 136         case SelfSuspendResumed:
 137                 return;
 138         case SelfSuspendWait:
 139                 mono_thread_info_wait_for_resume (info);
 140                 break;
 141         case SelfSuspendNotifyAndWait:
 142                 mono_threads_notify_initiator_of_suspend (info);
 143                 mono_thread_info_wait_for_resume (info);
 144                 break;
 145         }
 146 }
 147
 148 static void *
 149 return_stack_ptr ()
 150 {
 151         gpointer i;
 152         return &i;
 153 }
 154
 155 static void
 156 copy_stack_data (MonoThreadInfo *info, gpointer *stackdata_begin)
 157 {
 158         MonoThreadUnwindState *state;
 159         int stackdata_size;
 160         void* stackdata_end = return_stack_ptr ();
 161
 162         SAVE_REGS_ON_STACK;
 163
 164         state = &info->thread_saved_state [SELF_SUSPEND_STATE_INDEX];
 165
 166         stackdata_size = (char*)stackdata_begin - (char*)stackdata_end;
 167
 168         if (((gsize) stackdata_begin & (SIZEOF_VOID_P - 1)) != 0)
 169                 g_error ("stackdata_begin (%p) must be %d-byte aligned", stackdata_begin, SIZEOF_VOID_P);
 170         if (((gsize) stackdata_end & (SIZEOF_VOID_P - 1)) != 0)
 171                 g_error ("stackdata_end (%p) must be %d-byte aligned", stackdata_end, SIZEOF_VOID_P);
 172
 173         if (stackdata_size <= 0)
 174                 g_error ("stackdata_size = %d, but must be > 0, stackdata_begin = %p, stackdata_end = %p", stackdata_size, stackdata_begin, stackdata_end);
 175
 176         g_byte_array_set_size (info->stackdata, stackdata_size);
 177         state->gc_stackdata = info->stackdata->data;
 178         memcpy (state->gc_stackdata, stackdata_end, stackdata_size);
 179
 180         state->gc_stackdata_size = stackdata_size;
 181 }
 182
 183 static gpointer
 184 mono_threads_enter_gc_safe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata);
 185
 186 gpointer
 187 mono_threads_enter_gc_safe_region (gpointer *stackdata)
 188 {
 189         return mono_threads_enter_gc_safe_region_with_info (mono_thread_info_current_unchecked (), stackdata);
 190 }
 191
 192 gpointer
 193 mono_threads_enter_gc_safe_region_with_info (MonoThreadInfo *info, gpointer *stackdata)
 194 {
 195         gpointer cookie;
 196
 197         if (!mono_threads_is_coop_enabled ())
 198                 return NULL;
 199
 200         cookie = mono_threads_enter_gc_safe_region_unbalanced_with_info (info, stackdata);
 201
 202 #ifdef ENABLE_CHECKED_BUILD_GC
 203         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 204                 coop_tls_push (cookie);
 205 #endif
 206
 207         return cookie;
 208 }
 209
 210 gpointer
 211 mono_threads_enter_gc_safe_region_unbalanced (gpointer *stackdata)
 212 {
 213         return mono_threads_enter_gc_safe_region_unbalanced_with_info (mono_thread_info_current_unchecked (), stackdata);
 214 }
 215
 216 static gpointer
 217 mono_threads_enter_gc_safe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata)
 218 {
 219         if (!mono_threads_is_coop_enabled ())
 220                 return NULL;
 221
 222         ++coop_do_blocking_count;
 223
 224         check_info (info, "enter", "safe");
 225
 226         copy_stack_data (info, stackdata);
 227
 228 retry:
 229         ++coop_save_count;
 230         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 231
 232         switch (mono_threads_transition_do_blocking (info)) {
 233         case DoBlockingContinue:
 234                 break;
 235         case DoBlockingPollAndRetry:
 236                 mono_threads_state_poll_with_info (info);
 237                 goto retry;
 238         }
 239
 240         return info;
 241 }
 242
 243 void
 244 mono_threads_exit_gc_safe_region (gpointer cookie, gpointer *stackdata)
 245 {
 246         if (!mono_threads_is_coop_enabled ())
 247                 return;
 248
 249 #ifdef ENABLE_CHECKED_BUILD_GC
 250         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 251                 coop_tls_pop (cookie);
 252 #endif
 253
 254         mono_threads_exit_gc_safe_region_unbalanced (cookie, stackdata);
 255 }
 256
 257 void
 258 mono_threads_exit_gc_safe_region_unbalanced (gpointer cookie, gpointer *stackdata)
 259 {
 260         MonoThreadInfo *info;
 261
 262         if (!mono_threads_is_coop_enabled ())
 263                 return;
 264
 265         info = (MonoThreadInfo *)cookie;
 266
 267         check_info (info, "exit", "safe");
 268
 269         switch (mono_threads_transition_done_blocking (info)) {
 270         case DoneBlockingOk:
 271                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 272                 break;
 273         case DoneBlockingWait:
 274                 THREADS_SUSPEND_DEBUG ("state polling done, notifying of resume\n");
 275                 mono_thread_info_wait_for_resume (info);
 276                 break;
 277         default:
 278                 g_error ("Unknown thread state");
 279         }
 280 }
 281
 282 void
 283 mono_threads_assert_gc_safe_region (void)
 284 {
 285         MONO_REQ_GC_SAFE_MODE;
 286 }
 287
 288 gpointer
 289 mono_threads_enter_gc_unsafe_region (gpointer *stackdata)
 290 {
 291         return mono_threads_enter_gc_unsafe_region_with_info (mono_thread_info_current_unchecked (), stackdata);
 292 }
 293
 294 gpointer
 295 mono_threads_enter_gc_unsafe_region_with_info (THREAD_INFO_TYPE *info, gpointer *stackdata)
 296 {
 297         gpointer cookie;
 298
 299         if (!mono_threads_is_coop_enabled ())
 300                 return NULL;
 301
 302         cookie = mono_threads_enter_gc_unsafe_region_unbalanced_with_info (info, stackdata);
 303
 304 #ifdef ENABLE_CHECKED_BUILD_GC
 305         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 306                 coop_tls_push (cookie);
 307 #endif
 308
 309         return cookie;
 310 }
 311
 312 gpointer
 313 mono_threads_enter_gc_unsafe_region_unbalanced (gpointer *stackdata)
 314 {
 315         return mono_threads_enter_gc_unsafe_region_unbalanced_with_info (mono_thread_info_current_unchecked (), stackdata);
 316 }
 317
 318 gpointer
 319 mono_threads_enter_gc_unsafe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata)
 320 {
 321         if (!mono_threads_is_coop_enabled ())
 322                 return NULL;
 323
 324         ++coop_reset_blocking_count;
 325
 326         check_info (info, "enter", "unsafe");
 327
 328         copy_stack_data (info, stackdata);
 329
 330         switch (mono_threads_transition_abort_blocking (info)) {
 331         case AbortBlockingIgnore:
 332                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 333                 return NULL;
 334         case AbortBlockingIgnoreAndPoll:
 335                 mono_threads_state_poll_with_info (info);
 336                 return NULL;
 337         case AbortBlockingOk:
 338                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 339                 break;
 340         case AbortBlockingWait:
 341                 mono_thread_info_wait_for_resume (info);
 342                 break;
 343         default:
 344                 g_error ("Unknown thread state");
 345         }
 346
 347         return info;
 348 }
 349
 350 gpointer
 351 mono_threads_enter_gc_unsafe_region_cookie (void)
 352 {
 353         MonoThreadInfo *info;
 354
 355         g_assert (mono_threads_is_coop_enabled ());
 356
 357         info = mono_thread_info_current_unchecked ();
 358
 359         check_info (info, "enter (cookie)", "unsafe");
 360
 361 #ifdef ENABLE_CHECKED_BUILD_GC
 362         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 363                 coop_tls_push (info);
 364 #endif
 365
 366         return info;
 367 }
 368
 369 void
 370 mono_threads_exit_gc_unsafe_region (gpointer cookie, gpointer *stackdata)
 371 {
 372         if (!mono_threads_is_coop_enabled ())
 373                 return;
 374
 375 #ifdef ENABLE_CHECKED_BUILD_GC
 376         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 377                 coop_tls_pop (cookie);
 378 #endif
 379
 380         mono_threads_exit_gc_unsafe_region_unbalanced (cookie, stackdata);
 381 }
 382
 383 void
 384 mono_threads_exit_gc_unsafe_region_unbalanced (gpointer cookie, gpointer *stackdata)
 385 {
 386         if (!mono_threads_is_coop_enabled ())
 387                 return;
 388
 389         if (!cookie)
 390                 return;
 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 }