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  */
   9
  10 #include <config.h>
  11
  12 /* enable pthread extensions */
  13 #ifdef TARGET_MACH
  14 #define _DARWIN_C_SOURCE
  15 #endif
  16
  17 #include <mono/utils/mono-compiler.h>
  18 #include <mono/utils/mono-threads.h>
  19 #include <mono/utils/mono-tls.h>
  20 #include <mono/utils/hazard-pointer.h>
  21 #include <mono/utils/mono-memory-model.h>
  22 #include <mono/utils/mono-mmap.h>
  23 #include <mono/utils/atomic.h>
  24 #include <mono/utils/mono-time.h>
  25 #include <mono/utils/mono-counters.h>
  26 #include <mono/utils/mono-threads-coop.h>
  27 #include <mono/utils/mono-threads-api.h>
  28 #include <mono/utils/checked-build.h>
  29
  30 #ifdef TARGET_OSX
  31 #include <mono/utils/mach-support.h>
  32 #endif
  33
  34 #ifdef _MSC_VER
  35 // TODO: Find MSVC replacement for __builtin_unwind_init
  36 #define SAVE_REGS_ON_STACK g_assert_not_reached ();
  37 #else
  38 #define SAVE_REGS_ON_STACK __builtin_unwind_init ();
  39 #endif
  40
  41 volatile size_t mono_polling_required;
  42
  43 // FIXME: This would be more efficient if instead of instantiating the stack it just pushed a simple depth counter up and down,
  44 // perhaps with a per-thread cookie in the high bits.
  45 #ifdef ENABLE_CHECKED_BUILD_GC
  46 // Maintains a single per-thread stack of ints, used to ensure nesting is not violated
  47 MonoNativeTlsKey coop_reset_count_stack_key;
  48 static int coop_tls_push (int v) {
  49         GArray *stack = mono_native_tls_get_value (coop_reset_count_stack_key);
  50         if (!stack) {
  51                 stack = g_array_new (FALSE,FALSE,sizeof(int));
  52                 mono_native_tls_set_value (coop_reset_count_stack_key, stack);
  53         }
  54         g_array_append_val (stack, v);
  55         return stack->len;
  56 }
  57 static int coop_tls_pop (int *v) {
  58         GArray *stack = mono_native_tls_get_value (coop_reset_count_stack_key);
  59         if (!stack || 0 == stack->len)
  60                 return -1;
  61         stack->len--;
  62         *v = g_array_index (stack, int, stack->len);
  63         int len = stack->len;
  64         if (0 == len) {
  65                 g_array_free (stack,TRUE);
  66                 mono_native_tls_set_value (coop_reset_count_stack_key, NULL);
  67         }
  68         return len;
  69 }
  70 #endif
  71
  72 static int coop_reset_blocking_count;
  73 static int coop_try_blocking_count;
  74 static int coop_do_blocking_count;
  75 static int coop_do_polling_count;
  76 static int coop_save_count;
  77
  78 void
  79 mono_threads_state_poll (void)
  80 {
  81         MonoThreadInfo *info;
  82
  83         g_assert (mono_threads_is_coop_enabled ());
  84
  85         ++coop_do_polling_count;
  86
  87         info = mono_thread_info_current_unchecked ();
  88         if (!info)
  89                 return;
  90         THREADS_SUSPEND_DEBUG ("FINISH SELF SUSPEND OF %p\n", mono_thread_info_get_tid (info));
  91
  92         /* Fast check for pending suspend requests */
  93         if (!(info->thread_state & (STATE_ASYNC_SUSPEND_REQUESTED | STATE_SELF_SUSPEND_REQUESTED)))
  94                 return;
  95
  96         ++coop_save_count;
  97         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
  98
  99         /* commit the saved state and notify others if needed */
 100         switch (mono_threads_transition_state_poll (info)) {
 101         case SelfSuspendResumed:
 102                 return;
 103         case SelfSuspendWait:
 104                 mono_thread_info_wait_for_resume (info);
 105                 break;
 106         case SelfSuspendNotifyAndWait:
 107                 mono_threads_notify_initiator_of_suspend (info);
 108                 mono_thread_info_wait_for_resume (info);
 109                 break;
 110         }
 111 }
 112
 113 static void *
 114 return_stack_ptr ()
 115 {
 116         gpointer i;
 117         return &i;
 118 }
 119
 120 static void
 121 copy_stack_data (MonoThreadInfo *info, void* stackdata_begin)
 122 {
 123         MonoThreadUnwindState *state;
 124         int stackdata_size;
 125         void* stackdata_end = return_stack_ptr ();
 126
 127         SAVE_REGS_ON_STACK;
 128
 129         state = &info->thread_saved_state [SELF_SUSPEND_STATE_INDEX];
 130
 131         stackdata_size = (char*)stackdata_begin - (char*)stackdata_end;
 132
 133         if (((gsize) stackdata_begin & (SIZEOF_VOID_P - 1)) != 0)
 134                 g_error ("stackdata_begin (%p) must be %d-byte aligned", stackdata_begin, SIZEOF_VOID_P);
 135         if (((gsize) stackdata_end & (SIZEOF_VOID_P - 1)) != 0)
 136                 g_error ("stackdata_end (%p) must be %d-byte aligned", stackdata_end, SIZEOF_VOID_P);
 137
 138         if (stackdata_size <= 0)
 139                 g_error ("stackdata_size = %d, but must be > 0, stackdata_begin = %p, stackdata_end = %p", stackdata_size, stackdata_begin, stackdata_end);
 140
 141         g_byte_array_set_size (info->stackdata, stackdata_size);
 142         state->gc_stackdata = info->stackdata->data;
 143         memcpy (state->gc_stackdata, stackdata_end, stackdata_size);
 144
 145         state->gc_stackdata_size = stackdata_size;
 146 }
 147
 148 void*
 149 mono_threads_prepare_blocking (void* stackdata)
 150 {
 151         MonoThreadInfo *info;
 152
 153         if (!mono_threads_is_coop_enabled ())
 154                 return NULL;
 155
 156         ++coop_do_blocking_count;
 157
 158         info = mono_thread_info_current_unchecked ();
 159         /* If the thread is not attached, it doesn't make sense prepare for suspend. */
 160         if (!info || !mono_thread_info_is_live (info)) {
 161                 THREADS_SUSPEND_DEBUG ("PREPARE-BLOCKING failed %p\n", mono_thread_info_get_tid (info));
 162                 return NULL;
 163         }
 164
 165         copy_stack_data (info, stackdata);
 166
 167 retry:
 168         ++coop_save_count;
 169         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 170
 171         switch (mono_threads_transition_do_blocking (info)) {
 172         case DoBlockingContinue:
 173                 break;
 174         case DoBlockingPollAndRetry:
 175                 mono_threads_state_poll ();
 176                 goto retry;
 177         }
 178
 179         return info;
 180 }
 181
 182 void
 183 mono_threads_finish_blocking (void *cookie, void* stackdata)
 184 {
 185         static gboolean warned_about_bad_transition;
 186         MonoThreadInfo *info;
 187
 188         if (!mono_threads_is_coop_enabled ())
 189                 return;
 190
 191         info = (MonoThreadInfo *)cookie;
 192         if (!info)
 193                 return;
 194
 195         g_assert (info == mono_thread_info_current_unchecked ());
 196
 197         switch (mono_threads_transition_done_blocking (info)) {
 198         case DoneBlockingAborted:
 199                 if (!warned_about_bad_transition) {
 200                         warned_about_bad_transition = TRUE;
 201                         g_warning ("[%p] Blocking call ended in running state for, this might lead to unbound GC pauses.", mono_thread_info_get_tid (info));
 202                 }
 203                 mono_threads_state_poll ();
 204                 break;
 205         case DoneBlockingOk:
 206                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 207                 break;
 208         case DoneBlockingWait:
 209                 THREADS_SUSPEND_DEBUG ("state polling done, notifying of resume\n");
 210                 mono_thread_info_wait_for_resume (info);
 211                 break;
 212         default:
 213                 g_error ("Unknown thread state");
 214         }
 215 }
 216
 217
 218 void*
 219 mono_threads_reset_blocking_start (void* stackdata)
 220 {
 221         MonoThreadInfo *info;
 222
 223         if (!mono_threads_is_coop_enabled ())
 224                 return NULL;
 225
 226         info = mono_thread_info_current_unchecked ();
 227
 228 #ifdef ENABLE_CHECKED_BUILD_GC
 229         int reset_blocking_count = InterlockedIncrement (&coop_reset_blocking_count);
 230         // In this mode, the blocking count is used as the reset cookie. We would prefer
 231         // (but do not require) this to be unique across invocations and threads.
 232         if (reset_blocking_count == 0) // We *do* require it be nonzero
 233                 reset_blocking_count = coop_reset_blocking_count = 1;
 234 #else
 235         ++coop_reset_blocking_count;
 236 #endif
 237
 238         /* If the thread is not attached, it doesn't make sense prepare for suspend. */
 239         if (!info || !mono_thread_info_is_live (info))
 240                 return NULL;
 241
 242         copy_stack_data (info, stackdata);
 243
 244         switch (mono_threads_transition_abort_blocking (info)) {
 245         case AbortBlockingIgnore:
 246                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 247                 return NULL;
 248         case AbortBlockingIgnoreAndPoll:
 249                 mono_threads_state_poll ();
 250                 return NULL;
 251         case AbortBlockingOk:
 252                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 253                 break;
 254         case AbortBlockingOkAndPool:
 255                 mono_threads_state_poll ();
 256                 break;
 257         default:
 258                 g_error ("Unknown thread state");
 259         }
 260
 261 #ifdef ENABLE_CHECKED_BUILD_GC
 262         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC)) {
 263                 int level = coop_tls_push (reset_blocking_count);
 264                 //g_warning("Entering reset nest; level %d; cookie %d\n", level, reset_blocking_count);
 265                 return (void *)(intptr_t)reset_blocking_count;
 266         }
 267 #endif
 268
 269         return info;
 270 }
 271
 272 void
 273 mono_threads_reset_blocking_end (void *cookie, void* stackdata)
 274 {
 275         if (!mono_threads_is_coop_enabled ())
 276                 return;
 277
 278         if (!cookie)
 279                 return;
 280
 281 #ifdef ENABLE_CHECKED_BUILD_GC
 282         if (mono_check_mode_enabled (MONO_CHECK_MODE_GC)) {
 283                 int received_cookie = (int)(intptr_t)cookie;
 284                 int desired_cookie;
 285                 int level = coop_tls_pop (&desired_cookie);
 286                 //g_warning("Leaving reset nest; back to level %d; desired cookie %d; received cookie %d\n", level, desired_cookie, received_cookie);
 287                 if (level < 0)
 288                         mono_fatal_with_history ("Expected cookie %d but found no stack at all\n", desired_cookie);
 289                 if (desired_cookie != received_cookie)
 290                         mono_fatal_with_history ("Expected cookie %d but received %d\n", desired_cookie, received_cookie);
 291         } else // Notice this matches the line after the endif
 292 #endif
 293         {
 294                 g_assert (((MonoThreadInfo *)cookie) == mono_thread_info_current_unchecked ());
 295         }
 296
 297         mono_threads_prepare_blocking (stackdata);
 298 }
 299
 300 void
 301 mono_threads_init_coop (void)
 302 {
 303         if (!mono_threads_is_coop_enabled ())
 304                 return;
 305
 306         mono_counters_register ("Coop Reset Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_reset_blocking_count);
 307         mono_counters_register ("Coop Try Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_try_blocking_count);
 308         mono_counters_register ("Coop Do Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_blocking_count);
 309         mono_counters_register ("Coop Do Polling", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_polling_count);
 310         mono_counters_register ("Coop Save Count", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_save_count);
 311         //See the above for what's wrong here.
 312
 313 #ifdef ENABLE_CHECKED_BUILD_GC
 314         mono_native_tls_alloc (&coop_reset_count_stack_key, NULL);
 315 #endif
 316 }
 317
 318 void
 319 mono_threads_coop_begin_global_suspend (void)
 320 {
 321         if (mono_threads_is_coop_enabled ())
 322                 mono_polling_required = 1;
 323 }
 324
 325 void
 326 mono_threads_coop_end_global_suspend (void)
 327 {
 328         if (mono_threads_is_coop_enabled ())
 329                 mono_polling_required = 0;
 330 }
 331
 332 gpointer
 333 mono_threads_enter_gc_unsafe_region (gpointer* stackdata)
 334 {
 335         if (!mono_threads_is_coop_enabled ())
 336                 return NULL;
 337
 338         return mono_threads_reset_blocking_start (stackdata);
 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         mono_threads_reset_blocking_end (cookie, stackdata);
 348 }
 349
 350 void
 351 mono_threads_assert_gc_unsafe_region (void)
 352 {
 353         MONO_REQ_GC_UNSAFE_MODE;
 354 }
 355
 356 gpointer
 357 mono_threads_enter_gc_safe_region (gpointer *stackdata)
 358 {
 359         if (!mono_threads_is_coop_enabled ())
 360                 return NULL;
 361
 362         return mono_threads_prepare_blocking (stackdata);
 363 }
 364
 365 void
 366 mono_threads_exit_gc_safe_region (gpointer cookie, gpointer *stackdata)
 367 {
 368         if (!mono_threads_is_coop_enabled ())
 369                 return;
 370
 371         mono_threads_finish_blocking (cookie, stackdata);
 372 }
 373
 374 void
 375 mono_threads_assert_gc_safe_region (void)
 376 {
 377         MONO_REQ_GC_SAFE_MODE;
 378 }