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
  28 #ifdef TARGET_OSX
  29 #include <mono/utils/mach-support.h>
  30 #endif
  31
  32 #ifdef _MSC_VER
  33 // TODO: Find MSVC replacement for __builtin_unwind_init
  34 #define SAVE_REGS_ON_STACK g_assert_not_reached ();
  35 #else
  36 #define SAVE_REGS_ON_STACK __builtin_unwind_init ();
  37 #endif
  38
  39 volatile size_t mono_polling_required;
  40
  41 static int coop_reset_blocking_count;
  42 static int coop_try_blocking_count;
  43 static int coop_do_blocking_count;
  44 static int coop_do_polling_count;
  45 static int coop_save_count;
  46
  47 void
  48 mono_threads_state_poll (void)
  49 {
  50         MonoThreadInfo *info;
  51
  52         g_assert (mono_threads_is_coop_enabled ());
  53
  54         ++coop_do_polling_count;
  55
  56         info = mono_thread_info_current_unchecked ();
  57         if (!info)
  58                 return;
  59         THREADS_SUSPEND_DEBUG ("FINISH SELF SUSPEND OF %p\n", mono_thread_info_get_tid (info));
  60
  61         /* Fast check for pending suspend requests */
  62         if (!(info->thread_state & (STATE_ASYNC_SUSPEND_REQUESTED | STATE_SELF_SUSPEND_REQUESTED)))
  63                 return;
  64
  65         ++coop_save_count;
  66         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
  67
  68         /* commit the saved state and notify others if needed */
  69         switch (mono_threads_transition_state_poll (info)) {
  70         case SelfSuspendResumed:
  71                 return;
  72         case SelfSuspendWait:
  73                 mono_thread_info_wait_for_resume (info);
  74                 break;
  75         case SelfSuspendNotifyAndWait:
  76                 mono_threads_notify_initiator_of_suspend (info);
  77                 mono_thread_info_wait_for_resume (info);
  78                 break;
  79         }
  80 }
  81
  82 static void *
  83 return_stack_ptr ()
  84 {
  85         gpointer i;
  86         return &i;
  87 }
  88
  89 static void
  90 copy_stack_data (MonoThreadInfo *info, void* stackdata_begin)
  91 {
  92         MonoThreadUnwindState *state;
  93         int stackdata_size;
  94         void* stackdata_end = return_stack_ptr ();
  95
  96         SAVE_REGS_ON_STACK;
  97
  98         state = &info->thread_saved_state [SELF_SUSPEND_STATE_INDEX];
  99
 100         stackdata_size = (char*)stackdata_begin - (char*)stackdata_end;
 101
 102         if (((gsize) stackdata_begin & (SIZEOF_VOID_P - 1)) != 0)
 103                 g_error ("stackdata_begin (%p) must be %d-byte aligned", stackdata_begin, SIZEOF_VOID_P);
 104         if (((gsize) stackdata_end & (SIZEOF_VOID_P - 1)) != 0)
 105                 g_error ("stackdata_end (%p) must be %d-byte aligned", stackdata_end, SIZEOF_VOID_P);
 106
 107         if (stackdata_size <= 0)
 108                 g_error ("stackdata_size = %d, but must be > 0, stackdata_begin = %p, stackdata_end = %p", stackdata_size, stackdata_begin, stackdata_end);
 109
 110         g_byte_array_set_size (info->stackdata, stackdata_size);
 111         state->gc_stackdata = info->stackdata->data;
 112         memcpy (state->gc_stackdata, stackdata_end, stackdata_size);
 113
 114         state->gc_stackdata_size = stackdata_size;
 115 }
 116
 117 void*
 118 mono_threads_prepare_blocking (void* stackdata)
 119 {
 120         MonoThreadInfo *info;
 121
 122         if (!mono_threads_is_coop_enabled ())
 123                 return NULL;
 124
 125         ++coop_do_blocking_count;
 126
 127         info = mono_thread_info_current_unchecked ();
 128         /* If the thread is not attached, it doesn't make sense prepare for suspend. */
 129         if (!info || !mono_thread_info_is_live (info)) {
 130                 THREADS_SUSPEND_DEBUG ("PREPARE-BLOCKING failed %p\n", mono_thread_info_get_tid (info));
 131                 return NULL;
 132         }
 133
 134         copy_stack_data (info, stackdata);
 135
 136 retry:
 137         ++coop_save_count;
 138         mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
 139
 140         switch (mono_threads_transition_do_blocking (info)) {
 141         case DoBlockingContinue:
 142                 break;
 143         case DoBlockingPollAndRetry:
 144                 mono_threads_state_poll ();
 145                 goto retry;
 146         }
 147
 148         return info;
 149 }
 150
 151 void
 152 mono_threads_finish_blocking (void *cookie, void* stackdata)
 153 {
 154         static gboolean warned_about_bad_transition;
 155         MonoThreadInfo *info;
 156
 157         if (!mono_threads_is_coop_enabled ())
 158                 return;
 159
 160         info = cookie;
 161         if (!info)
 162                 return;
 163
 164         g_assert (info == mono_thread_info_current_unchecked ());
 165
 166         switch (mono_threads_transition_done_blocking (info)) {
 167         case DoneBlockingAborted:
 168                 if (!warned_about_bad_transition) {
 169                         warned_about_bad_transition = TRUE;
 170                         g_warning ("[%p] Blocking call ended in running state for, this might lead to unbound GC pauses.", mono_thread_info_get_tid (info));
 171                 }
 172                 mono_threads_state_poll ();
 173                 break;
 174         case DoneBlockingOk:
 175                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 176                 break;
 177         case DoneBlockingWait:
 178                 THREADS_SUSPEND_DEBUG ("state polling done, notifying of resume\n");
 179                 mono_thread_info_wait_for_resume (info);
 180                 break;
 181         default:
 182                 g_error ("Unknown thread state");
 183         }
 184 }
 185
 186
 187 void*
 188 mono_threads_reset_blocking_start (void* stackdata)
 189 {
 190         MonoThreadInfo *info;
 191
 192         if (!mono_threads_is_coop_enabled ())
 193                 return NULL;
 194
 195         ++coop_reset_blocking_count;
 196
 197         info = mono_thread_info_current_unchecked ();
 198         /* If the thread is not attached, it doesn't make sense prepare for suspend. */
 199         if (!info || !mono_thread_info_is_live (info))
 200                 return NULL;
 201
 202         copy_stack_data (info, stackdata);
 203
 204         switch (mono_threads_transition_abort_blocking (info)) {
 205         case AbortBlockingIgnore:
 206                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 207                 return NULL;
 208         case AbortBlockingIgnoreAndPoll:
 209                 mono_threads_state_poll ();
 210                 return NULL;
 211         case AbortBlockingOk:
 212                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 213                 return info;
 214         case AbortBlockingOkAndPool:
 215                 mono_threads_state_poll ();
 216                 return info;
 217         default:
 218                 g_error ("Unknown thread state");
 219         }
 220 }
 221
 222 void
 223 mono_threads_reset_blocking_end (void *cookie, void* stackdata)
 224 {
 225         MonoThreadInfo *info;
 226
 227         if (!mono_threads_is_coop_enabled ())
 228                 return;
 229
 230         info = cookie;
 231         if (!info)
 232                 return;
 233
 234         g_assert (info == mono_thread_info_current_unchecked ());
 235         mono_threads_prepare_blocking (stackdata);
 236 }
 237
 238 void
 239 mono_threads_init_coop (void)
 240 {
 241         if (!mono_threads_is_coop_enabled ())
 242                 return;
 243
 244         mono_counters_register ("Coop Reset Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_reset_blocking_count);
 245         mono_counters_register ("Coop Try Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_try_blocking_count);
 246         mono_counters_register ("Coop Do Blocking", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_blocking_count);
 247         mono_counters_register ("Coop Do Polling", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_do_polling_count);
 248         mono_counters_register ("Coop Save Count", MONO_COUNTER_GC | MONO_COUNTER_INT, &coop_save_count);
 249         //See the above for what's wrong here.
 250 }
 251
 252 void
 253 mono_threads_coop_begin_global_suspend (void)
 254 {
 255         if (mono_threads_is_coop_enabled ())
 256                 mono_polling_required = 1;
 257 }
 258
 259 void
 260 mono_threads_coop_end_global_suspend (void)
 261 {
 262         if (mono_threads_is_coop_enabled ())
 263                 mono_polling_required = 0;
 264 }
 265
 266 void*
 267 mono_threads_enter_gc_unsafe_region (void* stackdata)
 268 {
 269         if (!mono_threads_is_coop_enabled ())
 270                 return NULL;
 271
 272         return mono_threads_reset_blocking_start (stackdata);
 273 }
 274
 275 void
 276 mono_threads_exit_gc_unsafe_region (void *regions_cookie, void* stackdata)
 277 {
 278         if (!mono_threads_is_coop_enabled ())
 279                 return;
 280
 281         mono_threads_reset_blocking_end (regions_cookie, stackdata);
 282 }