base/tracked_objects.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/tracked_objects.h"
   6
   7 #include <math.h>
   8 #include <stdlib.h>
   9
  10 #include "base/compiler_specific.h"
  11 #include "base/debug/leak_annotations.h"
  12 #include "base/format_macros.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "base/port.h"
  15 #include "base/process/process_handle.h"
  16 #include "base/profiler/alternate_timer.h"
  17 #include "base/strings/stringprintf.h"
  18 #include "base/third_party/valgrind/memcheck.h"
  19 #include "base/threading/thread_restrictions.h"
  20
  21 using base::TimeDelta;
  22
  23 namespace tracked_objects {
  24
  25 namespace {
  26 // Flag to compile out almost all of the task tracking code.
  27 const bool kTrackAllTaskObjects = true;
  28
  29 // TODO(jar): Evaluate the perf impact of enabling this.  If the perf impact is
  30 // negligible, enable by default.
  31 // Flag to compile out parent-child link recording.
  32 const bool kTrackParentChildLinks = false;
  33
  34 // When ThreadData is first initialized, should we start in an ACTIVE state to
  35 // record all of the startup-time tasks, or should we start up DEACTIVATED, so
  36 // that we only record after parsing the command line flag --enable-tracking.
  37 // Note that the flag may force either state, so this really controls only the
  38 // period of time up until that flag is parsed. If there is no flag seen, then
  39 // this state may prevail for much or all of the process lifetime.
  40 const ThreadData::Status kInitialStartupState =
  41     ThreadData::PROFILING_CHILDREN_ACTIVE;
  42
  43 // Control whether an alternate time source (Now() function) is supported by
  44 // the ThreadData class.  This compile time flag should be set to true if we
  45 // want other modules (such as a memory allocator, or a thread-specific CPU time
  46 // clock) to be able to provide a thread-specific Now() function.  Without this
  47 // compile-time flag, the code will only support the wall-clock time.  This flag
  48 // can be flipped to efficiently disable this path (if there is a performance
  49 // problem with its presence).
  50 static const bool kAllowAlternateTimeSourceHandling = true;
  51
  52 }  // namespace
  53
  54 //------------------------------------------------------------------------------
  55 // DeathData tallies durations when a death takes place.
  56
  57 DeathData::DeathData() {
  58   Clear();
  59 }
  60
  61 DeathData::DeathData(int count) {
  62   Clear();
  63   count_ = count;
  64 }
  65
  66 // TODO(jar): I need to see if this macro to optimize branching is worth using.
  67 //
  68 // This macro has no branching, so it is surely fast, and is equivalent to:
  69 //             if (assign_it)
  70 //               target = source;
  71 // We use a macro rather than a template to force this to inline.
  72 // Related code for calculating max is discussed on the web.
  73 #define CONDITIONAL_ASSIGN(assign_it, target, source) \
  74     ((target) ^= ((target) ^ (source)) & -static_cast<int32>(assign_it))
  75
  76 void DeathData::RecordDeath(const int32 queue_duration,
  77                             const int32 run_duration,
  78                             int32 random_number) {
  79   // We'll just clamp at INT_MAX, but we should note this in the UI as such.
  80   if (count_ < INT_MAX)
  81     ++count_;
  82   queue_duration_sum_ += queue_duration;
  83   run_duration_sum_ += run_duration;
  84
  85   if (queue_duration_max_ < queue_duration)
  86     queue_duration_max_ = queue_duration;
  87   if (run_duration_max_ < run_duration)
  88     run_duration_max_ = run_duration;
  89
  90   // Take a uniformly distributed sample over all durations ever supplied.
  91   // The probability that we (instead) use this new sample is 1/count_.  This
  92   // results in a completely uniform selection of the sample (at least when we
  93   // don't clamp count_... but that should be inconsequentially likely).
  94   // We ignore the fact that we correlated our selection of a sample to the run
  95   // and queue times (i.e., we used them to generate random_number).
  96   CHECK_GT(count_, 0);
  97   if (0 == (random_number % count_)) {
  98     queue_duration_sample_ = queue_duration;
  99     run_duration_sample_ = run_duration;
 100   }
 101 }
 102
 103 int DeathData::count() const { return count_; }
 104
 105 int32 DeathData::run_duration_sum() const { return run_duration_sum_; }
 106
 107 int32 DeathData::run_duration_max() const { return run_duration_max_; }
 108
 109 int32 DeathData::run_duration_sample() const {
 110   return run_duration_sample_;
 111 }
 112
 113 int32 DeathData::queue_duration_sum() const {
 114   return queue_duration_sum_;
 115 }
 116
 117 int32 DeathData::queue_duration_max() const {
 118   return queue_duration_max_;
 119 }
 120
 121 int32 DeathData::queue_duration_sample() const {
 122   return queue_duration_sample_;
 123 }
 124
 125 void DeathData::ResetMax() {
 126   run_duration_max_ = 0;
 127   queue_duration_max_ = 0;
 128 }
 129
 130 void DeathData::Clear() {
 131   count_ = 0;
 132   run_duration_sum_ = 0;
 133   run_duration_max_ = 0;
 134   run_duration_sample_ = 0;
 135   queue_duration_sum_ = 0;
 136   queue_duration_max_ = 0;
 137   queue_duration_sample_ = 0;
 138 }
 139
 140 //------------------------------------------------------------------------------
 141 DeathDataSnapshot::DeathDataSnapshot()
 142     : count(-1),
 143       run_duration_sum(-1),
 144       run_duration_max(-1),
 145       run_duration_sample(-1),
 146       queue_duration_sum(-1),
 147       queue_duration_max(-1),
 148       queue_duration_sample(-1) {
 149 }
 150
 151 DeathDataSnapshot::DeathDataSnapshot(
 152     const tracked_objects::DeathData& death_data)
 153     : count(death_data.count()),
 154       run_duration_sum(death_data.run_duration_sum()),
 155       run_duration_max(death_data.run_duration_max()),
 156       run_duration_sample(death_data.run_duration_sample()),
 157       queue_duration_sum(death_data.queue_duration_sum()),
 158       queue_duration_max(death_data.queue_duration_max()),
 159       queue_duration_sample(death_data.queue_duration_sample()) {
 160 }
 161
 162 DeathDataSnapshot::~DeathDataSnapshot() {
 163 }
 164
 165 //------------------------------------------------------------------------------
 166 BirthOnThread::BirthOnThread(const Location& location,
 167                              const ThreadData& current)
 168     : location_(location),
 169       birth_thread_(&current) {
 170 }
 171
 172 //------------------------------------------------------------------------------
 173 BirthOnThreadSnapshot::BirthOnThreadSnapshot() {
 174 }
 175
 176 BirthOnThreadSnapshot::BirthOnThreadSnapshot(
 177     const tracked_objects::BirthOnThread& birth)
 178     : location(birth.location()),
 179       thread_name(birth.birth_thread()->thread_name()) {
 180 }
 181
 182 BirthOnThreadSnapshot::~BirthOnThreadSnapshot() {
 183 }
 184
 185 //------------------------------------------------------------------------------
 186 Births::Births(const Location& location, const ThreadData& current)
 187     : BirthOnThread(location, current),
 188       birth_count_(1) { }
 189
 190 int Births::birth_count() const { return birth_count_; }
 191
 192 void Births::RecordBirth() { ++birth_count_; }
 193
 194 void Births::ForgetBirth() { --birth_count_; }
 195
 196 void Births::Clear() { birth_count_ = 0; }
 197
 198 //------------------------------------------------------------------------------
 199 // ThreadData maintains the central data for all births and deaths on a single
 200 // thread.
 201
 202 // TODO(jar): We should pull all these static vars together, into a struct, and
 203 // optimize layout so that we benefit from locality of reference during accesses
 204 // to them.
 205
 206 // static
 207 NowFunction* ThreadData::now_function_ = NULL;
 208
 209 // A TLS slot which points to the ThreadData instance for the current thread. We
 210 // do a fake initialization here (zeroing out data), and then the real in-place
 211 // construction happens when we call tls_index_.Initialize().
 212 // static
 213 base::ThreadLocalStorage::StaticSlot ThreadData::tls_index_ = TLS_INITIALIZER;
 214
 215 // static
 216 int ThreadData::worker_thread_data_creation_count_ = 0;
 217
 218 // static
 219 int ThreadData::cleanup_count_ = 0;
 220
 221 // static
 222 int ThreadData::incarnation_counter_ = 0;
 223
 224 // static
 225 ThreadData* ThreadData::all_thread_data_list_head_ = NULL;
 226
 227 // static
 228 ThreadData* ThreadData::first_retired_worker_ = NULL;
 229
 230 // static
 231 base::LazyInstance<base::Lock>::Leaky
 232     ThreadData::list_lock_ = LAZY_INSTANCE_INITIALIZER;
 233
 234 // static
 235 ThreadData::Status ThreadData::status_ = ThreadData::UNINITIALIZED;
 236
 237 ThreadData::ThreadData(const std::string& suggested_name)
 238     : next_(NULL),
 239       next_retired_worker_(NULL),
 240       worker_thread_number_(0),
 241       incarnation_count_for_pool_(-1) {
 242   DCHECK_GE(suggested_name.size(), 0u);
 243   thread_name_ = suggested_name;
 244   PushToHeadOfList();  // Which sets real incarnation_count_for_pool_.
 245 }
 246
 247 ThreadData::ThreadData(int thread_number)
 248     : next_(NULL),
 249       next_retired_worker_(NULL),
 250       worker_thread_number_(thread_number),
 251       incarnation_count_for_pool_(-1)  {
 252   CHECK_GT(thread_number, 0);
 253   base::StringAppendF(&thread_name_, "WorkerThread-%d", thread_number);
 254   PushToHeadOfList();  // Which sets real incarnation_count_for_pool_.
 255 }
 256
 257 ThreadData::~ThreadData() {}
 258
 259 void ThreadData::PushToHeadOfList() {
 260   // Toss in a hint of randomness (atop the uniniitalized value).
 261   (void)VALGRIND_MAKE_MEM_DEFINED_IF_ADDRESSABLE(&random_number_,
 262                                                  sizeof(random_number_));
 263   MSAN_UNPOISON(&random_number_, sizeof(random_number_));
 264   random_number_ += static_cast<int32>(this - static_cast<ThreadData*>(0));
 265   random_number_ ^= (Now() - TrackedTime()).InMilliseconds();
 266
 267   DCHECK(!next_);
 268   base::AutoLock lock(*list_lock_.Pointer());
 269   incarnation_count_for_pool_ = incarnation_counter_;
 270   next_ = all_thread_data_list_head_;
 271   all_thread_data_list_head_ = this;
 272 }
 273
 274 // static
 275 ThreadData* ThreadData::first() {
 276   base::AutoLock lock(*list_lock_.Pointer());
 277   return all_thread_data_list_head_;
 278 }
 279
 280 ThreadData* ThreadData::next() const { return next_; }
 281
 282 // static
 283 void ThreadData::InitializeThreadContext(const std::string& suggested_name) {
 284   if (!Initialize())  // Always initialize if needed.
 285     return;
 286   ThreadData* current_thread_data =
 287       reinterpret_cast<ThreadData*>(tls_index_.Get());
 288   if (current_thread_data)
 289     return;  // Browser tests instigate this.
 290   current_thread_data = new ThreadData(suggested_name);
 291   tls_index_.Set(current_thread_data);
 292 }
 293
 294 // static
 295 ThreadData* ThreadData::Get() {
 296   if (!tls_index_.initialized())
 297     return NULL;  // For unittests only.
 298   ThreadData* registered = reinterpret_cast<ThreadData*>(tls_index_.Get());
 299   if (registered)
 300     return registered;
 301
 302   // We must be a worker thread, since we didn't pre-register.
 303   ThreadData* worker_thread_data = NULL;
 304   int worker_thread_number = 0;
 305   {
 306     base::AutoLock lock(*list_lock_.Pointer());
 307     if (first_retired_worker_) {
 308       worker_thread_data = first_retired_worker_;
 309       first_retired_worker_ = first_retired_worker_->next_retired_worker_;
 310       worker_thread_data->next_retired_worker_ = NULL;
 311     } else {
 312       worker_thread_number = ++worker_thread_data_creation_count_;
 313     }
 314   }
 315
 316   // If we can't find a previously used instance, then we have to create one.
 317   if (!worker_thread_data) {
 318     DCHECK_GT(worker_thread_number, 0);
 319     worker_thread_data = new ThreadData(worker_thread_number);
 320   }
 321   DCHECK_GT(worker_thread_data->worker_thread_number_, 0);
 322
 323   tls_index_.Set(worker_thread_data);
 324   return worker_thread_data;
 325 }
 326
 327 // static
 328 void ThreadData::OnThreadTermination(void* thread_data) {
 329   DCHECK(thread_data);  // TLS should *never* call us with a NULL.
 330   // We must NOT do any allocations during this callback. There is a chance
 331   // that the allocator is no longer active on this thread.
 332   if (!kTrackAllTaskObjects)
 333     return;  // Not compiled in.
 334   reinterpret_cast<ThreadData*>(thread_data)->OnThreadTerminationCleanup();
 335 }
 336
 337 void ThreadData::OnThreadTerminationCleanup() {
 338   // The list_lock_ was created when we registered the callback, so it won't be
 339   // allocated here despite the lazy reference.
 340   base::AutoLock lock(*list_lock_.Pointer());
 341   if (incarnation_counter_ != incarnation_count_for_pool_)
 342     return;  // ThreadData was constructed in an earlier unit test.
 343   ++cleanup_count_;
 344   // Only worker threads need to be retired and reused.
 345   if (!worker_thread_number_) {
 346     return;
 347   }
 348   // We must NOT do any allocations during this callback.
 349   // Using the simple linked lists avoids all allocations.
 350   DCHECK_EQ(this->next_retired_worker_, reinterpret_cast<ThreadData*>(NULL));
 351   this->next_retired_worker_ = first_retired_worker_;
 352   first_retired_worker_ = this;
 353 }
 354
 355 // static
 356 void ThreadData::Snapshot(bool reset_max, ProcessDataSnapshot* process_data) {
 357   // Add births that have run to completion to |collected_data|.
 358   // |birth_counts| tracks the total number of births recorded at each location
 359   // for which we have not seen a death count.
 360   BirthCountMap birth_counts;
 361   ThreadData::SnapshotAllExecutedTasks(reset_max, process_data, &birth_counts);
 362
 363   // Add births that are still active -- i.e. objects that have tallied a birth,
 364   // but have not yet tallied a matching death, and hence must be either
 365   // running, queued up, or being held in limbo for future posting.
 366   for (BirthCountMap::const_iterator it = birth_counts.begin();
 367        it != birth_counts.end(); ++it) {
 368     if (it->second > 0) {
 369       process_data->tasks.push_back(
 370           TaskSnapshot(*it->first, DeathData(it->second), "Still_Alive"));
 371     }
 372   }
 373 }
 374
 375 Births* ThreadData::TallyABirth(const Location& location) {
 376   BirthMap::iterator it = birth_map_.find(location);
 377   Births* child;
 378   if (it != birth_map_.end()) {
 379     child =  it->second;
 380     child->RecordBirth();
 381   } else {
 382     child = new Births(location, *this);  // Leak this.
 383     // Lock since the map may get relocated now, and other threads sometimes
 384     // snapshot it (but they lock before copying it).
 385     base::AutoLock lock(map_lock_);
 386     birth_map_[location] = child;
 387   }
 388
 389   if (kTrackParentChildLinks && status_ > PROFILING_ACTIVE &&
 390       !parent_stack_.empty()) {
 391     const Births* parent = parent_stack_.top();
 392     ParentChildPair pair(parent, child);
 393     if (parent_child_set_.find(pair) == parent_child_set_.end()) {
 394       // Lock since the map may get relocated now, and other threads sometimes
 395       // snapshot it (but they lock before copying it).
 396       base::AutoLock lock(map_lock_);
 397       parent_child_set_.insert(pair);
 398     }
 399   }
 400
 401   return child;
 402 }
 403
 404 void ThreadData::TallyADeath(const Births& birth,
 405                              int32 queue_duration,
 406                              int32 run_duration) {
 407   // Stir in some randomness, plus add constant in case durations are zero.
 408   const int32 kSomePrimeNumber = 2147483647;
 409   random_number_ += queue_duration + run_duration + kSomePrimeNumber;
 410   // An address is going to have some randomness to it as well ;-).
 411   random_number_ ^= static_cast<int32>(&birth - reinterpret_cast<Births*>(0));
 412
 413   // We don't have queue durations without OS timer. OS timer is automatically
 414   // used for task-post-timing, so the use of an alternate timer implies all
 415   // queue times are invalid.
 416   if (kAllowAlternateTimeSourceHandling && now_function_)
 417     queue_duration = 0;
 418
 419   DeathMap::iterator it = death_map_.find(&birth);
 420   DeathData* death_data;
 421   if (it != death_map_.end()) {
 422     death_data = &it->second;
 423   } else {
 424     base::AutoLock lock(map_lock_);  // Lock as the map may get relocated now.
 425     death_data = &death_map_[&birth];
 426   }  // Release lock ASAP.
 427   death_data->RecordDeath(queue_duration, run_duration, random_number_);
 428
 429   if (!kTrackParentChildLinks)
 430     return;
 431   if (!parent_stack_.empty()) {  // We might get turned off.
 432     DCHECK_EQ(parent_stack_.top(), &birth);
 433     parent_stack_.pop();
 434   }
 435 }
 436
 437 // static
 438 Births* ThreadData::TallyABirthIfActive(const Location& location) {
 439   if (!kTrackAllTaskObjects)
 440     return NULL;  // Not compiled in.
 441
 442   if (!TrackingStatus())
 443     return NULL;
 444   ThreadData* current_thread_data = Get();
 445   if (!current_thread_data)
 446     return NULL;
 447   return current_thread_data->TallyABirth(location);
 448 }
 449
 450 // static
 451 void ThreadData::TallyRunOnNamedThreadIfTracking(
 452     const base::TrackingInfo& completed_task,
 453     const TrackedTime& start_of_run,
 454     const TrackedTime& end_of_run) {
 455   if (!kTrackAllTaskObjects)
 456     return;  // Not compiled in.
 457
 458   // Even if we have been DEACTIVATED, we will process any pending births so
 459   // that our data structures (which counted the outstanding births) remain
 460   // consistent.
 461   const Births* birth = completed_task.birth_tally;
 462   if (!birth)
 463     return;
 464   ThreadData* current_thread_data = Get();
 465   if (!current_thread_data)
 466     return;
 467
 468   // Watch out for a race where status_ is changing, and hence one or both
 469   // of start_of_run or end_of_run is zero.  In that case, we didn't bother to
 470   // get a time value since we "weren't tracking" and we were trying to be
 471   // efficient by not calling for a genuine time value. For simplicity, we'll
 472   // use a default zero duration when we can't calculate a true value.
 473   int32 queue_duration = 0;
 474   int32 run_duration = 0;
 475   if (!start_of_run.is_null()) {
 476     queue_duration = (start_of_run - completed_task.EffectiveTimePosted())
 477         .InMilliseconds();
 478     if (!end_of_run.is_null())
 479       run_duration = (end_of_run - start_of_run).InMilliseconds();
 480   }
 481   current_thread_data->TallyADeath(*birth, queue_duration, run_duration);
 482 }
 483
 484 // static
 485 void ThreadData::TallyRunOnWorkerThreadIfTracking(
 486     const Births* birth,
 487     const TrackedTime& time_posted,
 488     const TrackedTime& start_of_run,
 489     const TrackedTime& end_of_run) {
 490   if (!kTrackAllTaskObjects)
 491     return;  // Not compiled in.
 492
 493   // Even if we have been DEACTIVATED, we will process any pending births so
 494   // that our data structures (which counted the outstanding births) remain
 495   // consistent.
 496   if (!birth)
 497     return;
 498
 499   // TODO(jar): Support the option to coalesce all worker-thread activity under
 500   // one ThreadData instance that uses locks to protect *all* access.  This will
 501   // reduce memory (making it provably bounded), but run incrementally slower
 502   // (since we'll use locks on TallyABirth and TallyADeath).  The good news is
 503   // that the locks on TallyADeath will be *after* the worker thread has run,
 504   // and hence nothing will be waiting for the completion (... besides some
 505   // other thread that might like to run).  Also, the worker threads tasks are
 506   // generally longer, and hence the cost of the lock may perchance be amortized
 507   // over the long task's lifetime.
 508   ThreadData* current_thread_data = Get();
 509   if (!current_thread_data)
 510     return;
 511
 512   int32 queue_duration = 0;
 513   int32 run_duration = 0;
 514   if (!start_of_run.is_null()) {
 515     queue_duration = (start_of_run - time_posted).InMilliseconds();
 516     if (!end_of_run.is_null())
 517       run_duration = (end_of_run - start_of_run).InMilliseconds();
 518   }
 519   current_thread_data->TallyADeath(*birth, queue_duration, run_duration);
 520 }
 521
 522 // static
 523 void ThreadData::TallyRunInAScopedRegionIfTracking(
 524     const Births* birth,
 525     const TrackedTime& start_of_run,
 526     const TrackedTime& end_of_run) {
 527   if (!kTrackAllTaskObjects)
 528     return;  // Not compiled in.
 529
 530   // Even if we have been DEACTIVATED, we will process any pending births so
 531   // that our data structures (which counted the outstanding births) remain
 532   // consistent.
 533   if (!birth)
 534     return;
 535
 536   ThreadData* current_thread_data = Get();
 537   if (!current_thread_data)
 538     return;
 539
 540   int32 queue_duration = 0;
 541   int32 run_duration = 0;
 542   if (!start_of_run.is_null() && !end_of_run.is_null())
 543     run_duration = (end_of_run - start_of_run).InMilliseconds();
 544   current_thread_data->TallyADeath(*birth, queue_duration, run_duration);
 545 }
 546
 547 // static
 548 void ThreadData::SnapshotAllExecutedTasks(bool reset_max,
 549                                           ProcessDataSnapshot* process_data,
 550                                           BirthCountMap* birth_counts) {
 551   if (!kTrackAllTaskObjects)
 552     return;  // Not compiled in.
 553
 554   // Get an unchanging copy of a ThreadData list.
 555   ThreadData* my_list = ThreadData::first();
 556
 557   // Gather data serially.
 558   // This hackish approach *can* get some slighly corrupt tallies, as we are
 559   // grabbing values without the protection of a lock, but it has the advantage
 560   // of working even with threads that don't have message loops.  If a user
 561   // sees any strangeness, they can always just run their stats gathering a
 562   // second time.
 563   for (ThreadData* thread_data = my_list;
 564        thread_data;
 565        thread_data = thread_data->next()) {
 566     thread_data->SnapshotExecutedTasks(reset_max, process_data, birth_counts);
 567   }
 568 }
 569
 570 void ThreadData::SnapshotExecutedTasks(bool reset_max,
 571                                        ProcessDataSnapshot* process_data,
 572                                        BirthCountMap* birth_counts) {
 573   // Get copy of data, so that the data will not change during the iterations
 574   // and processing.
 575   ThreadData::BirthMap birth_map;
 576   ThreadData::DeathMap death_map;
 577   ThreadData::ParentChildSet parent_child_set;
 578   SnapshotMaps(reset_max, &birth_map, &death_map, &parent_child_set);
 579
 580   for (ThreadData::DeathMap::const_iterator it = death_map.begin();
 581        it != death_map.end(); ++it) {
 582     process_data->tasks.push_back(
 583         TaskSnapshot(*it->first, it->second, thread_name()));
 584     (*birth_counts)[it->first] -= it->first->birth_count();
 585   }
 586
 587   for (ThreadData::BirthMap::const_iterator it = birth_map.begin();
 588        it != birth_map.end(); ++it) {
 589     (*birth_counts)[it->second] += it->second->birth_count();
 590   }
 591
 592   if (!kTrackParentChildLinks)
 593     return;
 594
 595   for (ThreadData::ParentChildSet::const_iterator it = parent_child_set.begin();
 596        it != parent_child_set.end(); ++it) {
 597     process_data->descendants.push_back(ParentChildPairSnapshot(*it));
 598   }
 599 }
 600
 601 // This may be called from another thread.
 602 void ThreadData::SnapshotMaps(bool reset_max,
 603                               BirthMap* birth_map,
 604                               DeathMap* death_map,
 605                               ParentChildSet* parent_child_set) {
 606   base::AutoLock lock(map_lock_);
 607   for (BirthMap::const_iterator it = birth_map_.begin();
 608        it != birth_map_.end(); ++it)
 609     (*birth_map)[it->first] = it->second;
 610   for (DeathMap::iterator it = death_map_.begin();
 611        it != death_map_.end(); ++it) {
 612     (*death_map)[it->first] = it->second;
 613     if (reset_max)
 614       it->second.ResetMax();
 615   }
 616
 617   if (!kTrackParentChildLinks)
 618     return;
 619
 620   for (ParentChildSet::iterator it = parent_child_set_.begin();
 621        it != parent_child_set_.end(); ++it)
 622     parent_child_set->insert(*it);
 623 }
 624
 625 // static
 626 void ThreadData::ResetAllThreadData() {
 627   ThreadData* my_list = first();
 628
 629   for (ThreadData* thread_data = my_list;
 630        thread_data;
 631        thread_data = thread_data->next())
 632     thread_data->Reset();
 633 }
 634
 635 void ThreadData::Reset() {
 636   base::AutoLock lock(map_lock_);
 637   for (DeathMap::iterator it = death_map_.begin();
 638        it != death_map_.end(); ++it)
 639     it->second.Clear();
 640   for (BirthMap::iterator it = birth_map_.begin();
 641        it != birth_map_.end(); ++it)
 642     it->second->Clear();
 643 }
 644
 645 static void OptionallyInitializeAlternateTimer() {
 646   NowFunction* alternate_time_source = GetAlternateTimeSource();
 647   if (alternate_time_source)
 648     ThreadData::SetAlternateTimeSource(alternate_time_source);
 649 }
 650
 651 bool ThreadData::Initialize() {
 652   if (!kTrackAllTaskObjects)
 653     return false;  // Not compiled in.
 654   if (status_ >= DEACTIVATED)
 655     return true;  // Someone else did the initialization.
 656   // Due to racy lazy initialization in tests, we'll need to recheck status_
 657   // after we acquire the lock.
 658
 659   // Ensure that we don't double initialize tls.  We are called when single
 660   // threaded in the product, but some tests may be racy and lazy about our
 661   // initialization.
 662   base::AutoLock lock(*list_lock_.Pointer());
 663   if (status_ >= DEACTIVATED)
 664     return true;  // Someone raced in here and beat us.
 665
 666   // Put an alternate timer in place if the environment calls for it, such as
 667   // for tracking TCMalloc allocations.  This insertion is idempotent, so we
 668   // don't mind if there is a race, and we'd prefer not to be in a lock while
 669   // doing this work.
 670   if (kAllowAlternateTimeSourceHandling)
 671     OptionallyInitializeAlternateTimer();
 672
 673   // Perform the "real" TLS initialization now, and leave it intact through
 674   // process termination.
 675   if (!tls_index_.initialized()) {  // Testing may have initialized this.
 676     DCHECK_EQ(status_, UNINITIALIZED);
 677     tls_index_.Initialize(&ThreadData::OnThreadTermination);
 678     if (!tls_index_.initialized())
 679       return false;
 680   } else {
 681     // TLS was initialzed for us earlier.
 682     DCHECK_EQ(status_, DORMANT_DURING_TESTS);
 683   }
 684
 685   // Incarnation counter is only significant to testing, as it otherwise will
 686   // never again change in this process.
 687   ++incarnation_counter_;
 688
 689   // The lock is not critical for setting status_, but it doesn't hurt. It also
 690   // ensures that if we have a racy initialization, that we'll bail as soon as
 691   // we get the lock earlier in this method.
 692   status_ = kInitialStartupState;
 693   if (!kTrackParentChildLinks &&
 694       kInitialStartupState == PROFILING_CHILDREN_ACTIVE)
 695     status_ = PROFILING_ACTIVE;
 696   DCHECK(status_ != UNINITIALIZED);
 697   return true;
 698 }
 699
 700 // static
 701 bool ThreadData::InitializeAndSetTrackingStatus(Status status) {
 702   DCHECK_GE(status, DEACTIVATED);
 703   DCHECK_LE(status, PROFILING_CHILDREN_ACTIVE);
 704
 705   if (!Initialize())  // No-op if already initialized.
 706     return false;  // Not compiled in.
 707
 708   if (!kTrackParentChildLinks && status > DEACTIVATED)
 709     status = PROFILING_ACTIVE;
 710   status_ = status;
 711   return true;
 712 }
 713
 714 // static
 715 ThreadData::Status ThreadData::status() {
 716   return status_;
 717 }
 718
 719 // static
 720 bool ThreadData::TrackingStatus() {
 721   return status_ > DEACTIVATED;
 722 }
 723
 724 // static
 725 bool ThreadData::TrackingParentChildStatus() {
 726   return status_ >= PROFILING_CHILDREN_ACTIVE;
 727 }
 728
 729 // static
 730 TrackedTime ThreadData::NowForStartOfRun(const Births* parent) {
 731   if (kTrackParentChildLinks && parent && status_ > PROFILING_ACTIVE) {
 732     ThreadData* current_thread_data = Get();
 733     if (current_thread_data)
 734       current_thread_data->parent_stack_.push(parent);
 735   }
 736   return Now();
 737 }
 738
 739 // static
 740 TrackedTime ThreadData::NowForEndOfRun() {
 741   return Now();
 742 }
 743
 744 // static
 745 void ThreadData::SetAlternateTimeSource(NowFunction* now_function) {
 746   DCHECK(now_function);
 747   if (kAllowAlternateTimeSourceHandling)
 748     now_function_ = now_function;
 749 }
 750
 751 // static
 752 TrackedTime ThreadData::Now() {
 753   if (kAllowAlternateTimeSourceHandling && now_function_)
 754     return TrackedTime::FromMilliseconds((*now_function_)());
 755   if (kTrackAllTaskObjects && TrackingStatus())
 756     return TrackedTime::Now();
 757   return TrackedTime();  // Super fast when disabled, or not compiled.
 758 }
 759
 760 // static
 761 void ThreadData::EnsureCleanupWasCalled(int major_threads_shutdown_count) {
 762   base::AutoLock lock(*list_lock_.Pointer());
 763   if (worker_thread_data_creation_count_ == 0)
 764     return;  // We haven't really run much, and couldn't have leaked.
 765   // Verify that we've at least shutdown/cleanup the major namesd threads.  The
 766   // caller should tell us how many thread shutdowns should have taken place by
 767   // now.
 768   return;  // TODO(jar): until this is working on XP, don't run the real test.
 769   CHECK_GT(cleanup_count_, major_threads_shutdown_count);
 770 }
 771
 772 // static
 773 void ThreadData::ShutdownSingleThreadedCleanup(bool leak) {
 774   // This is only called from test code, where we need to cleanup so that
 775   // additional tests can be run.
 776   // We must be single threaded... but be careful anyway.
 777   if (!InitializeAndSetTrackingStatus(DEACTIVATED))
 778     return;
 779   ThreadData* thread_data_list;
 780   {
 781     base::AutoLock lock(*list_lock_.Pointer());
 782     thread_data_list = all_thread_data_list_head_;
 783     all_thread_data_list_head_ = NULL;
 784     ++incarnation_counter_;
 785     // To be clean, break apart the retired worker list (though we leak them).
 786     while (first_retired_worker_) {
 787       ThreadData* worker = first_retired_worker_;
 788       CHECK_GT(worker->worker_thread_number_, 0);
 789       first_retired_worker_ = worker->next_retired_worker_;
 790       worker->next_retired_worker_ = NULL;
 791     }
 792   }
 793
 794   // Put most global static back in pristine shape.
 795   worker_thread_data_creation_count_ = 0;
 796   cleanup_count_ = 0;
 797   tls_index_.Set(NULL);
 798   status_ = DORMANT_DURING_TESTS;  // Almost UNINITIALIZED.
 799
 800   // To avoid any chance of racing in unit tests, which is the only place we
 801   // call this function, we may sometimes leak all the data structures we
 802   // recovered, as they may still be in use on threads from prior tests!
 803   if (leak) {
 804     ThreadData* thread_data = thread_data_list;
 805     while (thread_data) {
 806       ANNOTATE_LEAKING_OBJECT_PTR(thread_data);
 807       thread_data = thread_data->next();
 808     }
 809     return;
 810   }
 811
 812   // When we want to cleanup (on a single thread), here is what we do.
 813
 814   // Do actual recursive delete in all ThreadData instances.
 815   while (thread_data_list) {
 816     ThreadData* next_thread_data = thread_data_list;
 817     thread_data_list = thread_data_list->next();
 818
 819     for (BirthMap::iterator it = next_thread_data->birth_map_.begin();
 820          next_thread_data->birth_map_.end() != it; ++it)
 821       delete it->second;  // Delete the Birth Records.
 822     delete next_thread_data;  // Includes all Death Records.
 823   }
 824 }
 825
 826 //------------------------------------------------------------------------------
 827 TaskSnapshot::TaskSnapshot() {
 828 }
 829
 830 TaskSnapshot::TaskSnapshot(const BirthOnThread& birth,
 831                            const DeathData& death_data,
 832                            const std::string& death_thread_name)
 833     : birth(birth),
 834       death_data(death_data),
 835       death_thread_name(death_thread_name) {
 836 }
 837
 838 TaskSnapshot::~TaskSnapshot() {
 839 }
 840
 841 //------------------------------------------------------------------------------
 842 // ParentChildPairSnapshot
 843
 844 ParentChildPairSnapshot::ParentChildPairSnapshot() {
 845 }
 846
 847 ParentChildPairSnapshot::ParentChildPairSnapshot(
 848     const ThreadData::ParentChildPair& parent_child)
 849     : parent(*parent_child.first),
 850       child(*parent_child.second) {
 851 }
 852
 853 ParentChildPairSnapshot::~ParentChildPairSnapshot() {
 854 }
 855
 856 //------------------------------------------------------------------------------
 857 // ProcessDataSnapshot
 858
 859 ProcessDataSnapshot::ProcessDataSnapshot()
 860 #if !defined(OS_NACL)
 861     : process_id(base::GetCurrentProcId()) {
 862 #else
 863     : process_id(0) {
 864 #endif
 865 }
 866
 867 ProcessDataSnapshot::~ProcessDataSnapshot() {
 868 }
 869
 870 }  // namespace tracked_objects