mono/metadata/sgen-stw.c

   1 /*
   2  * sgen-stw.c: Stop the world functionality
   3  *
   4  * Author:
   5  *      Paolo Molaro (lupus@ximian.com)
   6  *  Rodrigo Kumpera (kumpera@gmail.com)
   7  *
   8  * Copyright 2005-2011 Novell, Inc (http://www.novell.com)
   9  * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
  10  * Copyright 2011 Xamarin, Inc.
  11  * Copyright (C) 2012 Xamarin Inc
  12  *
  13  * This library is free software; you can redistribute it and/or
  14  * modify it under the terms of the GNU Library General Public
  15  * License 2.0 as published by the Free Software Foundation;
  16  *
  17  * This library is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License 2.0 along with this library; if not, write to the Free
  24  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  25  */
  26
  27 #include "config.h"
  28 #ifdef HAVE_SGEN_GC
  29
  30 #include "metadata/sgen-gc.h"
  31 #include "metadata/sgen-protocol.h"
  32 #include "metadata/sgen-memory-governor.h"
  33 #include "metadata/profiler-private.h"
  34 #include "utils/mono-time.h"
  35 #include "utils/dtrace.h"
  36 #include "utils/mono-counters.h"
  37
  38 #define TV_DECLARE SGEN_TV_DECLARE
  39 #define TV_GETTIME SGEN_TV_GETTIME
  40 #define TV_ELAPSED SGEN_TV_ELAPSED
  41
  42 inline static void*
  43 align_pointer (void *ptr)
  44 {
  45         mword p = (mword)ptr;
  46         p += sizeof (gpointer) - 1;
  47         p &= ~ (sizeof (gpointer) - 1);
  48         return (void*)p;
  49 }
  50
  51 #ifdef USE_MONO_CTX
  52 static MonoContext cur_thread_ctx;
  53 #else
  54 static mword cur_thread_regs [ARCH_NUM_REGS];
  55 #endif
  56
  57 static void
  58 update_current_thread_stack (void *start)
  59 {
  60         int stack_guard = 0;
  61 #if !defined(USE_MONO_CTX)
  62         void *reg_ptr = cur_thread_regs;
  63 #endif
  64         SgenThreadInfo *info = mono_thread_info_current ();
  65
  66         info->stack_start = align_pointer (&stack_guard);
  67         g_assert (info->stack_start >= info->stack_start_limit && info->stack_start < info->stack_end);
  68 #ifdef USE_MONO_CTX
  69         MONO_CONTEXT_GET_CURRENT (cur_thread_ctx);
  70         memcpy (&info->ctx, &cur_thread_ctx, sizeof (MonoContext));
  71         if (mono_gc_get_gc_callbacks ()->thread_suspend_func)
  72                 mono_gc_get_gc_callbacks ()->thread_suspend_func (info->runtime_data, NULL, &info->ctx);
  73 #else
  74         ARCH_STORE_REGS (reg_ptr);
  75         memcpy (&info->regs, reg_ptr, sizeof (info->regs));
  76         if (mono_gc_get_gc_callbacks ()->thread_suspend_func)
  77                 mono_gc_get_gc_callbacks ()->thread_suspend_func (info->runtime_data, NULL, NULL);
  78 #endif
  79 }
  80
  81 static gboolean
  82 is_ip_in_managed_allocator (MonoDomain *domain, gpointer ip)
  83 {
  84         MonoJitInfo *ji;
  85
  86         if (!mono_thread_internal_current ())
  87                 /* Happens during thread attach */
  88                 return FALSE;
  89
  90         if (!ip || !domain)
  91                 return FALSE;
  92         if (!sgen_has_critical_method ())
  93                 return FALSE;
  94
  95         /*
  96          * mono_jit_info_table_find is not async safe since it calls into the AOT runtime to load information for
  97          * missing methods (#13951). To work around this, we disable the AOT fallback. For this to work, the JIT needs
  98          * to register the jit info for all GC critical methods after they are JITted/loaded.
  99          */
 100         ji = mono_jit_info_table_find_internal (domain, ip, FALSE);
 101         if (!ji)
 102                 return FALSE;
 103
 104         return sgen_is_critical_method (mono_jit_info_get_method (ji));
 105 }
 106
 107 static int
 108 restart_threads_until_none_in_managed_allocator (void)
 109 {
 110         SgenThreadInfo *info;
 111         int num_threads_died = 0;
 112         int sleep_duration = -1;
 113
 114         for (;;) {
 115                 int restart_count = 0, restarted_count = 0;
 116                 /* restart all threads that stopped in the
 117                    allocator */
 118                 FOREACH_THREAD_SAFE (info) {
 119                         gboolean result;
 120                         if (info->skip || info->gc_disabled || info->suspend_done)
 121                                 continue;
 122                         if (mono_thread_info_is_live (info) && (!info->stack_start || info->in_critical_region || info->info.inside_critical_region ||
 123                                         is_ip_in_managed_allocator (info->stopped_domain, info->stopped_ip))) {
 124                                 binary_protocol_thread_restart ((gpointer)mono_thread_info_get_tid (info));
 125                                 SGEN_LOG (3, "thread %p resumed.", (void*) (size_t) info->info.native_handle);
 126                                 result = sgen_resume_thread (info);
 127                                 if (result) {
 128                                         ++restart_count;
 129                                 } else {
 130                                         info->skip = 1;
 131                                 }
 132                         } else {
 133                                 /* we set the stopped_ip to
 134                                    NULL for threads which
 135                                    we're not restarting so
 136                                    that we can easily identify
 137                                    the others */
 138                                 info->stopped_ip = NULL;
 139                                 info->stopped_domain = NULL;
 140                                 info->suspend_done = TRUE;
 141                         }
 142                 } END_FOREACH_THREAD_SAFE
 143                 /* if no threads were restarted, we're done */
 144                 if (restart_count == 0)
 145                         break;
 146
 147                 /* wait for the threads to signal their restart */
 148                 sgen_wait_for_suspend_ack (restart_count);
 149
 150                 if (sleep_duration < 0) {
 151                         mono_thread_info_yield ();
 152                         sleep_duration = 0;
 153                 } else {
 154                         g_usleep (sleep_duration);
 155                         sleep_duration += 10;
 156                 }
 157
 158                 /* stop them again */
 159                 FOREACH_THREAD (info) {
 160                         gboolean result;
 161                         if (info->skip || info->stopped_ip == NULL)
 162                                 continue;
 163                         result = sgen_suspend_thread (info);
 164
 165                         if (result) {
 166                                 ++restarted_count;
 167                         } else {
 168                                 info->skip = 1;
 169                         }
 170                 } END_FOREACH_THREAD
 171                 /* some threads might have died */
 172                 num_threads_died += restart_count - restarted_count;
 173                 /* wait for the threads to signal their suspension
 174                    again */
 175                 sgen_wait_for_suspend_ack (restarted_count);
 176         }
 177
 178         return num_threads_died;
 179 }
 180
 181 static void
 182 acquire_gc_locks (void)
 183 {
 184         LOCK_INTERRUPTION;
 185         mono_thread_info_suspend_lock ();
 186 }
 187
 188 static void
 189 release_gc_locks (void)
 190 {
 191         mono_thread_info_suspend_unlock ();
 192         UNLOCK_INTERRUPTION;
 193 }
 194
 195 static void
 196 count_cards (long long *major_total, long long *major_marked, long long *los_total, long long *los_marked)
 197 {
 198         sgen_get_major_collector ()->count_cards (major_total, major_marked);
 199         sgen_los_count_cards (los_total, los_marked);
 200 }
 201
 202 static TV_DECLARE (stop_world_time);
 203 static unsigned long max_pause_usec = 0;
 204
 205 static guint64 time_stop_world;
 206 static guint64 time_restart_world;
 207
 208 /* LOCKING: assumes the GC lock is held */
 209 int
 210 sgen_stop_world (int generation)
 211 {
 212         TV_DECLARE (end_handshake);
 213         int count, dead;
 214
 215         mono_profiler_gc_event (MONO_GC_EVENT_PRE_STOP_WORLD, generation);
 216         MONO_GC_WORLD_STOP_BEGIN ();
 217         binary_protocol_world_stopping (sgen_timestamp ());
 218         acquire_gc_locks ();
 219
 220         /* We start to scan after locks are taking, this ensures we won't be interrupted. */
 221         sgen_process_togglerefs ();
 222
 223         update_current_thread_stack (&count);
 224
 225         sgen_global_stop_count++;
 226         SGEN_LOG (3, "stopping world n %d from %p %p", sgen_global_stop_count, mono_thread_info_current (), (gpointer)mono_native_thread_id_get ());
 227         TV_GETTIME (stop_world_time);
 228         count = sgen_thread_handshake (TRUE);
 229         dead = restart_threads_until_none_in_managed_allocator ();
 230         if (count < dead)
 231                 g_error ("More threads have died (%d) that been initialy suspended %d", dead, count);
 232         count -= dead;
 233
 234         SGEN_LOG (3, "world stopped %d thread(s)", count);
 235         mono_profiler_gc_event (MONO_GC_EVENT_POST_STOP_WORLD, generation);
 236         MONO_GC_WORLD_STOP_END ();
 237         if (binary_protocol_is_enabled ()) {
 238                 long long major_total = -1, major_marked = -1, los_total = -1, los_marked = -1;
 239                 if (binary_protocol_is_heavy_enabled ())
 240                         count_cards (&major_total, &major_marked, &los_total, &los_marked);
 241                 binary_protocol_world_stopped (sgen_timestamp (), major_total, major_marked, los_total, los_marked);
 242         }
 243
 244         TV_GETTIME (end_handshake);
 245         time_stop_world += TV_ELAPSED (stop_world_time, end_handshake);
 246
 247         sgen_memgov_collection_start (generation);
 248         if (sgen_need_bridge_processing ())
 249                 sgen_bridge_reset_data ();
 250
 251         return count;
 252 }
 253
 254 /* LOCKING: assumes the GC lock is held */
 255 int
 256 sgen_restart_world (int generation, GGTimingInfo *timing)
 257 {
 258         int count;
 259         SgenThreadInfo *info;
 260         TV_DECLARE (end_sw);
 261         TV_DECLARE (start_handshake);
 262         TV_DECLARE (end_bridge);
 263         unsigned long usec, bridge_usec;
 264
 265         if (binary_protocol_is_enabled ()) {
 266                 long long major_total = -1, major_marked = -1, los_total = -1, los_marked = -1;
 267                 if (binary_protocol_is_heavy_enabled ())
 268                         count_cards (&major_total, &major_marked, &los_total, &los_marked);
 269                 binary_protocol_world_restarting (generation, sgen_timestamp (), major_total, major_marked, los_total, los_marked);
 270         }
 271
 272         /* notify the profiler of the leftovers */
 273         /* FIXME this is the wrong spot at we can STW for non collection reasons. */
 274         if (G_UNLIKELY (mono_profiler_events & MONO_PROFILE_GC_MOVES))
 275                 sgen_gc_event_moves ();
 276         mono_profiler_gc_event (MONO_GC_EVENT_PRE_START_WORLD, generation);
 277         MONO_GC_WORLD_RESTART_BEGIN (generation);
 278         FOREACH_THREAD (info) {
 279                 info->stack_start = NULL;
 280 #ifdef USE_MONO_CTX
 281                 memset (&info->ctx, 0, sizeof (MonoContext));
 282 #else
 283                 memset (&info->regs, 0, sizeof (info->regs));
 284 #endif
 285         } END_FOREACH_THREAD
 286
 287         TV_GETTIME (start_handshake);
 288         count = sgen_thread_handshake (FALSE);
 289         TV_GETTIME (end_sw);
 290         time_restart_world += TV_ELAPSED (start_handshake, end_sw);
 291         usec = TV_ELAPSED (stop_world_time, end_sw);
 292         max_pause_usec = MAX (usec, max_pause_usec);
 293         SGEN_LOG (2, "restarted %d thread(s) (pause time: %d usec, max: %d)", count, (int)usec, (int)max_pause_usec);
 294         mono_profiler_gc_event (MONO_GC_EVENT_POST_START_WORLD, generation);
 295         MONO_GC_WORLD_RESTART_END (generation);
 296         binary_protocol_world_restarted (generation, sgen_timestamp ());
 297
 298         /*
 299          * We must release the thread info suspend lock after doing
 300          * the thread handshake.  Otherwise, if the GC stops the world
 301          * and a thread is in the process of starting up, but has not
 302          * yet registered (it's not in the thread_list), it is
 303          * possible that the thread does register while the world is
 304          * stopped.  When restarting the GC will then try to restart
 305          * said thread, but since it never got the suspend signal, it
 306          * cannot answer the restart signal, so a deadlock results.
 307          */
 308         release_gc_locks ();
 309
 310         sgen_try_free_some_memory = TRUE;
 311
 312         if (sgen_need_bridge_processing ())
 313                 sgen_bridge_processing_finish (generation);
 314
 315         TV_GETTIME (end_bridge);
 316         bridge_usec = TV_ELAPSED (end_sw, end_bridge);
 317
 318         if (timing) {
 319                 timing [0].stw_time = usec;
 320                 timing [0].bridge_time = bridge_usec;
 321         }
 322
 323         sgen_memgov_collection_end (generation, timing, timing ? 2 : 0);
 324
 325         return count;
 326 }
 327
 328 void
 329 sgen_init_stw (void)
 330 {
 331         mono_counters_register ("World stop", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_stop_world);
 332         mono_counters_register ("World restart", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_restart_world);
 333 }
 334
 335 #endif