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                 return;
 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
 149 static volatile gpointer* dummy_global;
 150
 151 static MONO_NEVER_INLINE
 152 void*
 153 return_stack_ptr (gpointer *i)
 154 {
 155         dummy_global = i;
 156         return i;
 157 }
 158
 159 static void
 160 copy_stack_data (MonoThreadInfo *info, gpointer *stackdata_begin)
 161 {
 162         MonoThreadUnwindState *state;
 163         int stackdata_size;
 164         gpointer dummy;
 165         void* stackdata_end = return_stack_ptr (&dummy);
 166
 167         SAVE_REGS_ON_STACK;
 168
 169         state = &info->thread_saved_state [SELF_SUSPEND_STATE_INDEX];
 170
 171         stackdata_size = (char*)stackdata_begin - (char*)stackdata_end;
 172
 173         if (((gsize) stackdata_begin & (SIZEOF_VOID_P - 1)) != 0)
 174                 g_error ("stackdata_begin (%p) must be %d-byte aligned", stackdata_begin, SIZEOF_VOID_P);
 175         if (((gsize) stackdata_end & (SIZEOF_VOID_P - 1)) != 0)
 176                 g_error ("stackdata_end (%p) must be %d-byte aligned", stackdata_end, SIZEOF_VOID_P);
 177
 178         if (stackdata_size <= 0)
 179                 g_error ("stackdata_size = %d, but must be > 0, stackdata_begin = %p, stackdata_end = %p", stackdata_size, stackdata_begin, stackdata_end);
 180
 181         g_byte_array_set_size (info->stackdata, stackdata_size);
 182         state->gc_stackdata = info->stackdata->data;
 183         memcpy (state->gc_stackdata, stackdata_end, stackdata_size);
 184
 185         state->gc_stackdata_size = stackdata_size;
 186 }
 187
 188 static gpointer
 189 mono_threads_enter_gc_safe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata);
 190
 191 gpointer
 192 mono_threads_enter_gc_safe_region (gpointer *stackdata)
 193 {
 194         return mono_threads_enter_gc_safe_region_with_info (mono_thread_info_current_unchecked (), stackdata);
 195 }
 196
 197 gpointer
 198 mono_threads_enter_gc_safe_region_with_info (MonoThreadInfo *info, gpointer *stackdata)
 199 {
 200         gpointer cookie;
 201
 202         if (!mono_threads_is_coop_enabled ())
 203                 return NULL;
 204
 205         cookie = mono_threads_enter_gc_safe_region_unbalanced_with_info (info, stackdata);
 206
 207 #ifdef ENABLE_CHECKED_BUILD_GC
 208         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 209                 coop_tls_push (cookie);
 210 #endif
 211
 212         return cookie;
 213 }
 214
 215 gpointer
 216 mono_threads_enter_gc_safe_region_unbalanced (gpointer *stackdata)
 217 {
 218         return mono_threads_enter_gc_safe_region_unbalanced_with_info (mono_thread_info_current_unchecked (), stackdata);
 219 }
 220
 221 static gpointer
 222 mono_threads_enter_gc_safe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata)
 223 {
 224         if (!mono_threads_is_coop_enabled ())
 225                 return NULL;
 226
 227         ++coop_do_blocking_count;
 228
 229         check_info (info, "enter", "safe");
 230
 231         copy_stack_data (info, stackdata);
 232
 233 retry:
 234         ++coop_save_count;
 235         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 236
 237         switch (mono_threads_transition_do_blocking (info)) {
 238         case DoBlockingContinue:
 239                 break;
 240         case DoBlockingPollAndRetry:
 241                 mono_threads_state_poll_with_info (info);
 242                 goto retry;
 243         }
 244
 245         return info;
 246 }
 247
 248 void
 249 mono_threads_exit_gc_safe_region (gpointer cookie, gpointer *stackdata)
 250 {
 251         if (!mono_threads_is_coop_enabled ())
 252                 return;
 253
 254 #ifdef ENABLE_CHECKED_BUILD_GC
 255         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 256                 coop_tls_pop (cookie);
 257 #endif
 258
 259         mono_threads_exit_gc_safe_region_unbalanced (cookie, stackdata);
 260 }
 261
 262 void
 263 mono_threads_exit_gc_safe_region_unbalanced (gpointer cookie, gpointer *stackdata)
 264 {
 265         MonoThreadInfo *info;
 266
 267         if (!mono_threads_is_coop_enabled ())
 268                 return;
 269
 270         info = (MonoThreadInfo *)cookie;
 271
 272         check_info (info, "exit", "safe");
 273
 274         switch (mono_threads_transition_done_blocking (info)) {
 275         case DoneBlockingOk:
 276                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 277                 break;
 278         case DoneBlockingWait:
 279                 THREADS_SUSPEND_DEBUG ("state polling done, notifying of resume\n");
 280                 mono_thread_info_wait_for_resume (info);
 281                 break;
 282         default:
 283                 g_error ("Unknown thread state");
 284         }
 285 }
 286
 287 void
 288 mono_threads_assert_gc_safe_region (void)
 289 {
 290         MONO_REQ_GC_SAFE_MODE;
 291 }
 292
 293 gpointer
 294 mono_threads_enter_gc_unsafe_region (gpointer *stackdata)
 295 {
 296         return mono_threads_enter_gc_unsafe_region_with_info (mono_thread_info_current_unchecked (), stackdata);
 297 }
 298
 299 gpointer
 300 mono_threads_enter_gc_unsafe_region_with_info (THREAD_INFO_TYPE *info, gpointer *stackdata)
 301 {
 302         gpointer cookie;
 303
 304         if (!mono_threads_is_coop_enabled ())
 305                 return NULL;
 306
 307         cookie = mono_threads_enter_gc_unsafe_region_unbalanced_with_info (info, stackdata);
 308
 309 #ifdef ENABLE_CHECKED_BUILD_GC
 310         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 311                 coop_tls_push (cookie);
 312 #endif
 313
 314         return cookie;
 315 }
 316
 317 gpointer
 318 mono_threads_enter_gc_unsafe_region_unbalanced (gpointer *stackdata)
 319 {
 320         return mono_threads_enter_gc_unsafe_region_unbalanced_with_info (mono_thread_info_current_unchecked (), stackdata);
 321 }
 322
 323 gpointer
 324 mono_threads_enter_gc_unsafe_region_unbalanced_with_info (MonoThreadInfo *info, gpointer *stackdata)
 325 {
 326         if (!mono_threads_is_coop_enabled ())
 327                 return NULL;
 328
 329         ++coop_reset_blocking_count;
 330
 331         check_info (info, "enter", "unsafe");
 332
 333         copy_stack_data (info, stackdata);
 334
 335         switch (mono_threads_transition_abort_blocking (info)) {
 336         case AbortBlockingIgnore:
 337                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 338                 return NULL;
 339         case AbortBlockingIgnoreAndPoll:
 340                 mono_threads_state_poll_with_info (info);
 341                 return NULL;
 342         case AbortBlockingOk:
 343                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 344                 break;
 345         case AbortBlockingWait:
 346                 mono_thread_info_wait_for_resume (info);
 347                 break;
 348         default:
 349                 g_error ("Unknown thread state");
 350         }
 351
 352         return info;
 353 }
 354
 355 gpointer
 356 mono_threads_enter_gc_unsafe_region_cookie (void)
 357 {
 358         MonoThreadInfo *info;
 359
 360         g_assert (mono_threads_is_coop_enabled ());
 361
 362         info = mono_thread_info_current_unchecked ();
 363
 364         check_info (info, "enter (cookie)", "unsafe");
 365
 366 #ifdef ENABLE_CHECKED_BUILD_GC
 367         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 368                 coop_tls_push (info);
 369 #endif
 370
 371         return info;
 372 }
 373
 374 void
 375 mono_threads_exit_gc_unsafe_region (gpointer cookie, gpointer *stackdata)
 376 {
 377         if (!mono_threads_is_coop_enabled ())
 378                 return;
 379
 380 #ifdef ENABLE_CHECKED_BUILD_GC
 381         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC))
 382                 coop_tls_pop (cookie);
 383 #endif
 384
 385         mono_threads_exit_gc_unsafe_region_unbalanced (cookie, stackdata);
 386 }
 387
 388 void
 389 mono_threads_exit_gc_unsafe_region_unbalanced (gpointer cookie, gpointer *stackdata)
 390 {
 391         if (!mono_threads_is_coop_enabled ())
 392                 return;
 393
 394         if (!cookie)
 395                 return;
 396
 397         mono_threads_enter_gc_safe_region_unbalanced (stackdata);
 398 }
 399
 400 void
 401 mono_threads_assert_gc_unsafe_region (void)
 402 {
 403         MONO_REQ_GC_UNSAFE_MODE;
 404 }
 405
 406 gboolean
 407 mono_threads_is_coop_enabled (void)
 408 {
 409 #if defined(USE_COOP_GC)
 410         return TRUE;
 411 #else
 412         static int is_coop_enabled = -1;
 413         if (G_UNLIKELY (is_coop_enabled == -1))
 414                 is_coop_enabled = g_getenv ("MONO_ENABLE_COOP") != NULL ? 1 : 0;
 415         return is_coop_enabled == 1;
 416 #endif
 417 }
 418
 419
 420 void
 421 mono_threads_coop_init (void)
 422 {
 423         if (!mono_threads_is_coop_enabled ())
 424                 return;
 425
 426         mono_counters_register ("Coop Reset Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_reset_blocking_count);
 427         mono_counters_register ("Coop Try Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_try_blocking_count);
 428         mono_counters_register ("Coop Do Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_blocking_count);
 429         mono_counters_register ("Coop Do Polling", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_polling_count);
 430         mono_counters_register ("Coop Save Count", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_save_count);
 431         //See the above for what's wrong here.
 432
 433 #ifdef ENABLE_CHECKED_BUILD_GC
 434         mono_native_tls_alloc (&coop_reset_count_stack_key, NULL);
 435 #endif
 436 }
 437
 438 void
 439 mono_threads_coop_begin_global_suspend (void)
 440 {
 441         if (mono_threads_is_coop_enabled ())
 442                 mono_polling_required = 1;
 443 }
 444
 445 void
 446 mono_threads_coop_end_global_suspend (void)
 447 {
 448         if (mono_threads_is_coop_enabled ())
 449                 mono_polling_required = 0;
 450 }