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 <mono/utils/mono-compiler.h>
  11 #include <mono/utils/mono-semaphore.h>
  12 #include <mono/utils/mono-threads.h>
  13 #include <mono/utils/mono-tls.h>
  14 #include <mono/utils/hazard-pointer.h>
  15 #include <mono/utils/mono-memory-model.h>
  16 #include <mono/utils/mono-mmap.h>
  17 #include <mono/utils/atomic.h>
  18 #include <mono/utils/mono-time.h>
  19
  20 #ifdef USE_COOP_BACKEND
  21
  22 volatile size_t mono_polling_required;
  23
  24 void
  25 mono_threads_state_poll (void)
  26 {
  27         MonoThreadInfo *info;
  28
  29         info = mono_thread_info_current_unchecked ();
  30         if (!info)
  31                 return;
  32         THREADS_SUSPEND_DEBUG ("FINISH SELF SUSPEND OF %p\n", mono_thread_info_get_tid (info));
  33
  34         /* Fast check for pending suspend requests */
  35         if (!(info->thread_state & (STATE_ASYNC_SUSPEND_REQUESTED | STATE_SELF_SUSPEND_REQUESTED)))
  36                 return;
  37
  38         g_assert (mono_threads_get_runtime_callbacks ()->thread_state_init_from_sigctx (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX], NULL));
  39
  40         /* commit the saved state and notify others if needed */
  41         switch (mono_threads_transition_state_poll (info)) {
  42         case SelfSuspendResumed:
  43                 return;
  44         case SelfSuspendWait:
  45                 mono_thread_info_wait_for_resume (info);
  46                 break;
  47         case SelfSuspendNotifyAndWait:
  48                 mono_threads_notify_initiator_of_suspend (info);
  49                 mono_thread_info_wait_for_resume (info);
  50                 break;
  51         }
  52 }
  53
  54 void*
  55 mono_threads_prepare_blocking (void)
  56 {
  57         MonoThreadInfo *info;
  58
  59         info = mono_thread_info_current_unchecked ();
  60         /* If the thread is not attached, it doesn't make sense prepare for suspend. */
  61         if (!info || !mono_thread_info_is_live (info)) {
  62                 THREADS_SUSPEND_DEBUG ("PREPARE-BLOCKING failed %p\n", mono_thread_info_get_tid (info));
  63                 return NULL;
  64         }
  65
  66 retry:
  67         /*The JIT might not be able to save*/
  68         if (!mono_threads_get_runtime_callbacks ()->thread_state_init_from_sigctx (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX], NULL)) {
  69                 THREADS_SUSPEND_DEBUG ("PREPARE-BLOCKING failed %p to save thread state\n", mono_thread_info_get_tid (info));
  70                 return NULL;
  71         }
  72
  73         switch (mono_threads_transition_do_blocking (info)) {
  74         case DoBlockingContinue:
  75                 break;
  76         case DoBlockingPollAndRetry:
  77                 mono_threads_state_poll ();
  78                 goto retry;
  79         }
  80
  81         return info;
  82 }
  83
  84 void
  85 mono_threads_finish_blocking (void *cookie)
  86 {
  87         static gboolean warned_about_bad_transition;
  88         MonoThreadInfo *info = cookie;
  89
  90         if (!info)
  91                 return;
  92
  93         g_assert (info == mono_thread_info_current_unchecked ());
  94
  95         switch (mono_threads_transition_done_blocking (info)) {
  96         case DoneBlockingAborted:
  97                 if (!warned_about_bad_transition) {
  98                         warned_about_bad_transition = TRUE;
  99                         g_warning ("[%p] Blocking call ended in running state for, this might lead to unbound GC pauses.", mono_thread_info_get_tid (info));
 100                 }
 101                 mono_threads_state_poll ();
 102                 break;
 103         case DoneBlockingOk:
 104                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 105                 break;
 106         case DoneBlockingWait:
 107                 THREADS_SUSPEND_DEBUG ("state polling done, notifying of resume\n");
 108                 mono_thread_info_wait_for_resume (info);
 109                 break;
 110         default:
 111                 g_error ("Unknown thread state");
 112         }
 113 }
 114
 115
 116 void*
 117 mono_threads_reset_blocking_start (void)
 118 {
 119         MonoThreadInfo *info = mono_thread_info_current_unchecked ();
 120
 121         /* If the thread is not attached, it doesn't make sense prepare for suspend. */
 122         if (!info || !mono_thread_info_is_live (info))
 123                 return NULL;
 124
 125         switch (mono_threads_transition_abort_blocking (info)) {
 126         case AbortBlockingIgnore:
 127                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 128                 return NULL;
 129         case AbortBlockingIgnoreAndPoll:
 130                 mono_threads_state_poll ();
 131                 return NULL;
 132         case AbortBlockingOk:
 133                 info->thread_saved_state [SELF_SUSPEND_STATE_INDEX].valid = FALSE;
 134                 return info;
 135         case AbortBlockingOkAndPool:
 136                 mono_threads_state_poll ();
 137                 return info;
 138         default:
 139                 g_error ("Unknown thread state");
 140         }
 141 }
 142
 143 void
 144 mono_threads_reset_blocking_end (void *cookie)
 145 {
 146         MonoThreadInfo *info = cookie;
 147
 148         if (!info)
 149                 return;
 150
 151         g_assert (info == mono_thread_info_current_unchecked ());
 152         mono_threads_prepare_blocking ();
 153 }
 154
 155 void*
 156 mono_threads_try_prepare_blocking (void)
 157 {
 158         MonoThreadInfo *info;
 159
 160         info = mono_thread_info_current_unchecked ();
 161         /* If the thread is not attached, it doesn't make sense prepare for suspend. */
 162         if (!info || !mono_thread_info_is_live (info) || mono_thread_info_current_state (info) == STATE_BLOCKING) {
 163                 THREADS_SUSPEND_DEBUG ("PREPARE-TRY-BLOCKING failed %p\n", mono_thread_info_get_tid (info));
 164                 return NULL;
 165         }
 166
 167 retry:
 168         /*The JIT might not be able to save*/
 169         if (!mono_threads_get_runtime_callbacks ()->thread_state_init_from_sigctx (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX], NULL)) {
 170                 THREADS_SUSPEND_DEBUG ("PREPARE-TRY-BLOCKING failed %p to save thread state\n", mono_thread_info_get_tid (info));
 171                 return NULL;
 172         }
 173
 174         switch (mono_threads_transition_do_blocking (info)) {
 175         case DoBlockingContinue:
 176                 break;
 177         case DoBlockingPollAndRetry:
 178                 mono_threads_state_poll ();
 179                 goto retry;
 180         }
 181
 182         return info;
 183 }
 184
 185 void
 186 mono_threads_finish_try_blocking (void* cookie)
 187 {
 188         mono_threads_finish_blocking (cookie);
 189 }
 190
 191 void
 192 mono_threads_core_abort_syscall (MonoThreadInfo *info)
 193 {
 194         g_error ("FIXME");
 195 }
 196
 197 gboolean
 198 mono_threads_core_begin_async_resume (MonoThreadInfo *info)
 199 {
 200         g_error ("FIXME");
 201         return FALSE;
 202 }
 203
 204 gboolean
 205 mono_threads_core_begin_async_suspend (MonoThreadInfo *info, gboolean interrupt_kernel)
 206 {
 207         mono_threads_add_to_pending_operation_set (info);
 208         /* There's nothing else to do after we async request the thread to suspend */
 209         return TRUE;
 210 }
 211
 212 gboolean
 213 mono_threads_core_check_suspend_result (MonoThreadInfo *info)
 214 {
 215         /* Async suspend can't async fail on coop */
 216         return TRUE;
 217 }
 218
 219 gboolean
 220 mono_threads_core_needs_abort_syscall (void)
 221 {
 222         /*
 223         Small digression.
 224         Syscall abort can't be handled by the suspend machinery even though it's kind of implemented
 225         in a similar way (with, like, signals).
 226
 227         So, having it here is wrong, it should be on mono-threads-(mach|posix|windows).
 228         Ideally we would slice this in (coop|preemp) and target. Then have this file set:
 229         mono-threads-mach, mono-threads-mach-preempt and mono-threads-mach-coop.
 230         More files, less ifdef hell.
 231         */
 232         return FALSE;
 233 }
 234
 235 void
 236 mono_threads_init_platform (void)
 237 {
 238         //See the above for what's wrong here.
 239 }
 240
 241 void
 242 mono_threads_platform_free (MonoThreadInfo *info)
 243 {
 244         //See the above for what's wrong here.
 245 }
 246
 247 void
 248 mono_threads_platform_register (MonoThreadInfo *info)
 249 {
 250         //See the above for what's wrong here.
 251 }
 252
 253 void
 254 mono_threads_core_begin_global_suspend (void)
 255 {
 256         mono_polling_required = 1;
 257 }
 258
 259 void
 260 mono_threads_core_end_global_suspend (void)
 261 {
 262         mono_polling_required = 0;
 263 }
 264
 265
 266 #endif