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 volatile gpointer* dummy_global;
 149
 150 static MONO_NEVER_INLINE
 151 void*
 152 return_stack_ptr (gpointer *i)
 153 {
 154         dummy_global = i;
 155         return i;
 156 }
 157
 158 static void
 159 copy_stack_data (MonoThreadInfo *info, gpointer *stackdata_begin)
 160 {
 161         MonoThreadUnwindState *state;
 162         int stackdata_size;
 163         gpointer dummy;
 164         void* stackdata_end = return_stack_ptr (&dummy);
 165
 166         SAVE_REGS_ON_STACK;
 167
 168         state = &info->thread_saved_state [SELF_SUSPEND_STATE_INDEX];
 169
 170         stackdata_size = (char*)stackdata_begin - (char*)stackdata_end;
 171
 172         if (((gsize) stackdata_begin & (SIZEOF_VOID_P - 1)) != 0)
 173                 g_error ("stackdata_begin (%p) must be %d-byte aligned", stackdata_begin, SIZEOF_VOID_P);
 174         if (((gsize) stackdata_end & (SIZEOF_VOID_P - 1)) != 0)
 175                 g_error ("stackdata_end (%p) must be %d-byte aligned", stackdata_end, SIZEOF_VOID_P);
 176
 177         if (stackdata_size <= 0)
 178                 g_error ("stackdata_size = %d, but must be > 0, stackdata_begin = %p, stackdata_end = %p", stackdata_size, stackdata_begin, stackdata_end);
 179
 180         g_byte_array_set_size (info->stackdata, stackdata_size);
 181         state->gc_stackdata = info->stackdata->data;
 182         memcpy (state->gc_stackdata, stackdata_end, stackdata_size);
 183
 184         state->gc_stackdata_size = stackdata_size;
 185 }
 186
 187 static gpointer
 188 mono_threads_enter_gc_safe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata);
 189
 190 gpointer
 191 mono_threads_enter_gc_safe_region (gpointer *stackdata)
 192 {
 193         return mono_threads_enter_gc_safe_region_with_info (mono_thread_info_current_unchecked (), stackdata);
 194 }
 195
 196 gpointer
 197 mono_threads_enter_gc_safe_region_with_info (MonoThreadInfo *info, gpointer *stackdata)
 198 {
 199         gpointer cookie;
 200
 201         if (!mono_threads_is_coop_enabled ())
 202                 return NULL;
 203
 204         cookie = mono_threads_enter_gc_safe_region_unbalanced_with_info (info, stackdata);
 205
 206 #ifdef ENABLE_CHECKED_BUILD_GC
 207         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 208                 coop_tls_push (cookie);
 209 #endif
 210
 211         return cookie;
 212 }
 213
 214 gpointer
 215 mono_threads_enter_gc_safe_region_unbalanced (gpointer *stackdata)
 216 {
 217         return mono_threads_enter_gc_safe_region_unbalanced_with_info (mono_thread_info_current_unchecked (), stackdata);
 218 }
 219
 220 static gpointer
 221 mono_threads_enter_gc_safe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata)
 222 {
 223         if (!mono_threads_is_coop_enabled ())
 224                 return NULL;
 225
 226         ++coop_do_blocking_count;
 227
 228         check_info (info, "enter", "safe");
 229
 230         copy_stack_data (info, stackdata);
 231
 232 retry:
 233         ++coop_save_count;
 234         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 235
 236         switch (mono_threads_transition_do_blocking (info)) {
 237         case DoBlockingContinue:
 238                 break;
 239         case DoBlockingPollAndRetry:
 240                 mono_threads_state_poll_with_info (info);
 241                 goto retry;
 242         }
 243
 244         return info;
 245 }
 246
 247 void
 248 mono_threads_exit_gc_safe_region (gpointer cookie, gpointer *stackdata)
 249 {
 250         if (!mono_threads_is_coop_enabled ())
 251                 return;
 252
 253 #ifdef ENABLE_CHECKED_BUILD_GC
 254         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 255                 coop_tls_pop (cookie);
 256 #endif
 257
 258         mono_threads_exit_gc_safe_region_unbalanced (cookie, stackdata);
 259 }
 260
 261 void
 262 mono_threads_exit_gc_safe_region_unbalanced (gpointer cookie, gpointer *stackdata)
 263 {
 264         MonoThreadInfo *info;
 265
 266         if (!mono_threads_is_coop_enabled ())
 267                 return;
 268
 269         info = (MonoThreadInfo *)cookie;
 270
 271         check_info (info, "exit", "safe");
 272
 273         switch (mono_threads_transition_done_blocking (info)) {
 274         case DoneBlockingOk:
 275                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 276                 break;
 277         case DoneBlockingWait:
 278                 THREADS_SUSPEND_DEBUG ("state polling done, notifying of resume\n");
 279                 mono_thread_info_wait_for_resume (info);
 280                 break;
 281         default:
 282                 g_error ("Unknown thread state");
 283         }
 284 }
 285
 286 void
 287 mono_threads_assert_gc_safe_region (void)
 288 {
 289         MONO_REQ_GC_SAFE_MODE;
 290 }
 291
 292 gpointer
 293 mono_threads_enter_gc_unsafe_region (gpointer *stackdata)
 294 {
 295         return mono_threads_enter_gc_unsafe_region_with_info (mono_thread_info_current_unchecked (), stackdata);
 296 }
 297
 298 gpointer
 299 mono_threads_enter_gc_unsafe_region_with_info (THREAD_INFO_TYPE *info, gpointer *stackdata)
 300 {
 301         gpointer cookie;
 302
 303         if (!mono_threads_is_coop_enabled ())
 304                 return NULL;
 305
 306         cookie = mono_threads_enter_gc_unsafe_region_unbalanced_with_info (info, stackdata);
 307
 308 #ifdef ENABLE_CHECKED_BUILD_GC
 309         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 310                 coop_tls_push (cookie);
 311 #endif
 312
 313         return cookie;
 314 }
 315
 316 gpointer
 317 mono_threads_enter_gc_unsafe_region_unbalanced (gpointer *stackdata)
 318 {
 319         return mono_threads_enter_gc_unsafe_region_unbalanced_with_info (mono_thread_info_current_unchecked (), stackdata);
 320 }
 321
 322 gpointer
 323 mono_threads_enter_gc_unsafe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata)
 324 {
 325         if (!mono_threads_is_coop_enabled ())
 326                 return NULL;
 327
 328         ++coop_reset_blocking_count;
 329
 330         check_info (info, "enter", "unsafe");
 331
 332         copy_stack_data (info, stackdata);
 333
 334         switch (mono_threads_transition_abort_blocking (info)) {
 335         case AbortBlockingIgnore:
 336                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 337                 return NULL;
 338         case AbortBlockingIgnoreAndPoll:
 339                 mono_threads_state_poll_with_info (info);
 340                 return NULL;
 341         case AbortBlockingOk:
 342                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 343                 break;
 344         case AbortBlockingWait:
 345                 mono_thread_info_wait_for_resume (info);
 346                 break;
 347         default:
 348                 g_error ("Unknown thread state");
 349         }
 350
 351         return info;
 352 }
 353
 354 gpointer
 355 mono_threads_enter_gc_unsafe_region_cookie (void)
 356 {
 357         MonoThreadInfo *info;
 358
 359         g_assert (mono_threads_is_coop_enabled ());
 360
 361         info = mono_thread_info_current_unchecked ();
 362
 363         check_info (info, "enter (cookie)", "unsafe");
 364
 365 #ifdef ENABLE_CHECKED_BUILD_GC
 366         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 367                 coop_tls_push (info);
 368 #endif
 369
 370         return info;
 371 }
 372
 373 void
 374 mono_threads_exit_gc_unsafe_region (gpointer cookie, gpointer *stackdata)
 375 {
 376         if (!mono_threads_is_coop_enabled ())
 377                 return;
 378
 379 #ifdef ENABLE_CHECKED_BUILD_GC
 380         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 381                 coop_tls_pop (cookie);
 382 #endif
 383
 384         mono_threads_exit_gc_unsafe_region_unbalanced (cookie, stackdata);
 385 }
 386
 387 void
 388 mono_threads_exit_gc_unsafe_region_unbalanced (gpointer cookie, gpointer *stackdata)
 389 {
 390         if (!mono_threads_is_coop_enabled ())
 391                 return;
 392
 393         if (!cookie)
 394                 return;
 395
 396         mono_threads_enter_gc_safe_region_unbalanced (stackdata);
 397 }
 398
 399 void
 400 mono_threads_assert_gc_unsafe_region (void)
 401 {
 402         MONO_REQ_GC_UNSAFE_MODE;
 403 }
 404
 405 gboolean
 406 mono_threads_is_coop_enabled (void)
 407 {
 408 #if defined(USE_COOP_GC)
 409         return TRUE;
 410 #else
 411         static int is_coop_enabled = -1;
 412         if (G_UNLIKELY (is_coop_enabled == -1))
 413                 is_coop_enabled = g_getenv ("MONO_ENABLE_COOP") != NULL ? 1 : 0;
 414         return is_coop_enabled == 1;
 415 #endif
 416 }
 417
 418
 419 void
 420 mono_threads_coop_init (void)
 421 {
 422         if (!mono_threads_is_coop_enabled ())
 423                 return;
 424
 425         mono_counters_register ("Coop Reset Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_reset_blocking_count);
 426         mono_counters_register ("Coop Try Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_try_blocking_count);
 427         mono_counters_register ("Coop Do Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_blocking_count);
 428         mono_counters_register ("Coop Do Polling", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_polling_count);
 429         mono_counters_register ("Coop Save Count", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_save_count);
 430         //See the above for what's wrong here.
 431
 432 #ifdef ENABLE_CHECKED_BUILD_GC
 433         mono_native_tls_alloc (&coop_reset_count_stack_key, NULL);
 434 #endif
 435 }
 436
 437 void
 438 mono_threads_coop_begin_global_suspend (void)
 439 {
 440         if (mono_threads_is_coop_enabled ())
 441                 mono_polling_required = 1;
 442 }
 443
 444 void
 445 mono_threads_coop_end_global_suspend (void)
 446 {
 447         if (mono_threads_is_coop_enabled ())
 448                 mono_polling_required = 0;
 449 }