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 #define TV_ELAPSED_MS SGEN_TV_ELAPSED_MS
  42
  43 inline static void*
  44 align_pointer (void *ptr)
  45 {
  46         mword p = (mword)ptr;
  47         p += sizeof (gpointer) - 1;
  48         p &= ~ (sizeof (gpointer) - 1);
  49         return (void*)p;
  50 }
  51
  52 #ifdef USE_MONO_CTX
  53 static MonoContext cur_thread_ctx = {0};
  54 #else
  55 static mword cur_thread_regs [ARCH_NUM_REGS] = {0};
  56 #endif
  57
  58 static void
  59 update_current_thread_stack (void *start)
  60 {
  61         int stack_guard = 0;
  62 #if !defined(USE_MONO_CTX)
  63         void *reg_ptr = cur_thread_regs;
  64 #endif
  65         SgenThreadInfo *info = mono_thread_info_current ();
  66
  67         info->stack_start = align_pointer (&stack_guard);
  68         g_assert (info->stack_start >= info->stack_start_limit && info->stack_start < info->stack_end);
  69 #ifdef USE_MONO_CTX
  70         MONO_CONTEXT_GET_CURRENT (cur_thread_ctx);
  71         memcpy (&info->ctx, &cur_thread_ctx, sizeof (MonoContext));
  72         if (mono_gc_get_gc_callbacks ()->thread_suspend_func)
  73                 mono_gc_get_gc_callbacks ()->thread_suspend_func (info->runtime_data, NULL, &info->ctx);
  74 #else
  75         ARCH_STORE_REGS (reg_ptr);
  76         memcpy (&info->regs, reg_ptr, sizeof (info->regs));
  77         if (mono_gc_get_gc_callbacks ()->thread_suspend_func)
  78                 mono_gc_get_gc_callbacks ()->thread_suspend_func (info->runtime_data, NULL, NULL);
  79 #endif
  80 }
  81
  82 static gboolean
  83 is_ip_in_managed_allocator (MonoDomain *domain, gpointer ip)
  84 {
  85         MonoJitInfo *ji;
  86
  87         if (!mono_thread_internal_current ())
  88                 /* Happens during thread attach */
  89                 return FALSE;
  90
  91         if (!ip || !domain)
  92                 return FALSE;
  93         if (!sgen_has_critical_method ())
  94                 return FALSE;
  95
  96         /*
  97          * mono_jit_info_table_find is not async safe since it calls into the AOT runtime to load information for
  98          * missing methods (#13951). To work around this, we disable the AOT fallback. For this to work, the JIT needs
  99          * to register the jit info for all GC critical methods after they are JITted/loaded.
 100          */
 101         ji = mono_jit_info_table_find_internal (domain, ip, FALSE);
 102         if (!ji)
 103                 return FALSE;
 104
 105         return sgen_is_critical_method (mono_jit_info_get_method (ji));
 106 }
 107
 108 static int
 109 restart_threads_until_none_in_managed_allocator (void)
 110 {
 111         SgenThreadInfo *info;
 112         int num_threads_died = 0;
 113         int sleep_duration = -1;
 114
 115         for (;;) {
 116                 int restart_count = 0, restarted_count = 0;
 117                 /* restart all threads that stopped in the
 118                    allocator */
 119                 FOREACH_THREAD_SAFE (info) {
 120                         gboolean result;
 121                         if (info->skip || info->gc_disabled)
 122                                 continue;
 123                         if (mono_thread_info_run_state (info) == STATE_RUNNING && (!info->stack_start || info->in_critical_region || info->info.inside_critical_region ||
 124                                         is_ip_in_managed_allocator (info->stopped_domain, info->stopped_ip))) {
 125                                 binary_protocol_thread_restart ((gpointer)mono_thread_info_get_tid (info));
 126                                 SGEN_LOG (3, "thread %p resumed.", (void*) (size_t) info->info.native_handle);
 127                                 result = sgen_resume_thread (info);
 128                                 if (result) {
 129                                         ++restart_count;
 130                                 } else {
 131                                         info->skip = 1;
 132                                 }
 133                         } else {
 134                                 /* we set the stopped_ip to
 135                                    NULL for threads which
 136                                    we're not restarting so
 137                                    that we can easily identify
 138                                    the others */
 139                                 info->stopped_ip = NULL;
 140                                 info->stopped_domain = NULL;
 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 long long time_stop_world;
 206 static long long 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, major_marked, los_total, los_marked;
 239                 count_cards (&major_total, &major_marked, &los_total, &los_marked);
 240                 binary_protocol_world_stopped (sgen_timestamp (), major_total, major_marked, los_total, los_marked);
 241         }
 242
 243         TV_GETTIME (end_handshake);
 244         time_stop_world += TV_ELAPSED (stop_world_time, end_handshake);
 245
 246         sgen_memgov_collection_start (generation);
 247         if (sgen_need_bridge_processing ())
 248                 sgen_bridge_reset_data ();
 249
 250         return count;
 251 }
 252
 253 /* LOCKING: assumes the GC lock is held */
 254 int
 255 sgen_restart_world (int generation, GGTimingInfo *timing)
 256 {
 257         int count;
 258         SgenThreadInfo *info;
 259         TV_DECLARE (end_sw);
 260         TV_DECLARE (start_handshake);
 261         TV_DECLARE (end_bridge);
 262         unsigned long usec, bridge_usec;
 263
 264         if (binary_protocol_is_enabled ()) {
 265                 long long major_total, major_marked, los_total, los_marked;
 266                 count_cards (&major_total, &major_marked, &los_total, &los_marked);
 267                 binary_protocol_world_restarting (generation, sgen_timestamp (), major_total, major_marked, los_total, los_marked);
 268         }
 269
 270         /* notify the profiler of the leftovers */
 271         /* FIXME this is the wrong spot at we can STW for non collection reasons. */
 272         if (G_UNLIKELY (mono_profiler_events & MONO_PROFILE_GC_MOVES))
 273                 sgen_gc_event_moves ();
 274         mono_profiler_gc_event (MONO_GC_EVENT_PRE_START_WORLD, generation);
 275         MONO_GC_WORLD_RESTART_BEGIN (generation);
 276         FOREACH_THREAD (info) {
 277                 info->stack_start = NULL;
 278 #ifdef USE_MONO_CTX
 279                 memset (&info->ctx, 0, sizeof (MonoContext));
 280 #else
 281                 memset (&info->regs, 0, sizeof (info->regs));
 282 #endif
 283         } END_FOREACH_THREAD
 284
 285         TV_GETTIME (start_handshake);
 286         count = sgen_thread_handshake (FALSE);
 287         TV_GETTIME (end_sw);
 288         time_restart_world += TV_ELAPSED (start_handshake, end_sw);
 289         usec = TV_ELAPSED (stop_world_time, end_sw);
 290         max_pause_usec = MAX (usec, max_pause_usec);
 291         SGEN_LOG (2, "restarted %d thread(s) (pause time: %d usec, max: %d)", count, (int)usec, (int)max_pause_usec);
 292         mono_profiler_gc_event (MONO_GC_EVENT_POST_START_WORLD, generation);
 293         MONO_GC_WORLD_RESTART_END (generation);
 294         binary_protocol_world_restarted (generation, sgen_timestamp ());
 295
 296         /*
 297          * We must release the thread info suspend lock after doing
 298          * the thread handshake.  Otherwise, if the GC stops the world
 299          * and a thread is in the process of starting up, but has not
 300          * yet registered (it's not in the thread_list), it is
 301          * possible that the thread does register while the world is
 302          * stopped.  When restarting the GC will then try to restart
 303          * said thread, but since it never got the suspend signal, it
 304          * cannot answer the restart signal, so a deadlock results.
 305          */
 306         release_gc_locks ();
 307
 308         sgen_try_free_some_memory = TRUE;
 309
 310         if (sgen_need_bridge_processing ())
 311                 sgen_bridge_processing_finish (generation);
 312
 313         TV_GETTIME (end_bridge);
 314         bridge_usec = TV_ELAPSED (end_sw, end_bridge);
 315
 316         if (timing) {
 317                 timing [0].stw_time = usec;
 318                 timing [0].bridge_time = bridge_usec;
 319         }
 320
 321         sgen_memgov_collection_end (generation, timing, timing ? 2 : 0);
 322
 323         return count;
 324 }
 325
 326 void
 327 sgen_init_stw (void)
 328 {
 329         mono_counters_register ("World stop", MONO_COUNTER_GC | MONO_COUNTER_LONG | MONO_COUNTER_TIME, &time_stop_world);
 330         mono_counters_register ("World restart", MONO_COUNTER_GC | MONO_COUNTER_LONG | MONO_COUNTER_TIME, &time_restart_world);
 331 }
 332
 333 #endif