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