summaryrefslogtreecommitdiff
path: root/xpcom/threads/BackgroundHangMonitor.cpp
blob: b0b41e291e011ba5ac448ca48fb980e0f45e3fa0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/ArrayUtils.h"
#include "mozilla/BackgroundHangMonitor.h"
#include "mozilla/LinkedList.h"
#include "mozilla/Monitor.h"
#include "mozilla/Move.h"
#include "mozilla/Preferences.h"
#include "mozilla/StaticPtr.h"
#include "mozilla/ThreadLocal.h"

#include "prinrval.h"
#include "prthread.h"
#include "nsIObserverService.h"
#include "nsIObserver.h"
#include "mozilla/Services.h"
#include "nsXULAppAPI.h"

#include <algorithm>

// Activate BHR only for one every BHR_BETA_MOD users.
// This is now 100% of Beta population for the Beta 45/46 e10s A/B trials
// It can be scaled back again in the future
#define BHR_BETA_MOD 1;

// Maximum depth of the call stack in the reported thread hangs. This value represents
// the 99.9th percentile of the thread hangs stack depths reported.
static const size_t kMaxThreadHangStackDepth = 30;

// An utility comparator function used by std::unique to collapse "(* script)" entries in
// a vector representing a call stack.
bool StackScriptEntriesCollapser(const char* aStackEntry, const char *aAnotherStackEntry)
{
  return !strcmp(aStackEntry, aAnotherStackEntry) &&
         (!strcmp(aStackEntry, "(chrome script)") || !strcmp(aStackEntry, "(content script)"));
}

namespace mozilla {

/**
 * BackgroundHangManager is the global object that
 * manages all instances of BackgroundHangThread.
 */
class BackgroundHangManager : public nsIObserver
{
private:
  // Background hang monitor thread function
  static void MonitorThread(void* aData)
  {
    PR_SetCurrentThreadName("BgHangManager");

    /* We do not hold a reference to BackgroundHangManager here
       because the monitor thread only exists as long as the
       BackgroundHangManager instance exists. We stop the monitor
       thread in the BackgroundHangManager destructor, and we can
       only get to the destructor if we don't hold a reference here. */
    static_cast<BackgroundHangManager*>(aData)->RunMonitorThread();
  }

  // Hang monitor thread
  PRThread* mHangMonitorThread;
  // Stop hang monitoring
  bool mShutdown;

  BackgroundHangManager(const BackgroundHangManager&);
  BackgroundHangManager& operator=(const BackgroundHangManager&);
  void RunMonitorThread();

public:
  NS_DECL_THREADSAFE_ISUPPORTS
  NS_DECL_NSIOBSERVER
  static StaticRefPtr<BackgroundHangManager> sInstance;
  static bool sDisabled;

  // Lock for access to members of this class
  Monitor mLock;
  // Current time as seen by hang monitors
  PRIntervalTime mIntervalNow;
  // List of BackgroundHangThread instances associated with each thread
  LinkedList<BackgroundHangThread> mHangThreads;

  void Shutdown()
  {
    MonitorAutoLock autoLock(mLock);
    mShutdown = true;
    autoLock.Notify();
  }

  void Wakeup()
  {
    // PR_CreateThread could have failed earlier
    if (mHangMonitorThread) {
      // Use PR_Interrupt to avoid potentially taking a lock
      PR_Interrupt(mHangMonitorThread);
    }
  }

  BackgroundHangManager();
private:
  virtual ~BackgroundHangManager();
};

NS_IMPL_ISUPPORTS(BackgroundHangManager, nsIObserver)

NS_IMETHODIMP
BackgroundHangManager::Observe(nsISupports* aSubject, const char* aTopic, const char16_t* aData) {
  NS_ENSURE_TRUE(!strcmp(aTopic, "profile-after-change"), NS_ERROR_UNEXPECTED);
  BackgroundHangMonitor::DisableOnBeta();

  nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
  MOZ_ASSERT(observerService);
  observerService->RemoveObserver(this, "profile-after-change");

  return NS_OK;
}

/**
 * BackgroundHangThread is a per-thread object that is used
 * by all instances of BackgroundHangMonitor to monitor hangs.
 */
class BackgroundHangThread : public LinkedListElement<BackgroundHangThread>
{
private:
  static MOZ_THREAD_LOCAL(BackgroundHangThread*) sTlsKey;
  static bool sTlsKeyInitialized;

  BackgroundHangThread(const BackgroundHangThread&);
  BackgroundHangThread& operator=(const BackgroundHangThread&);
  ~BackgroundHangThread();

  /* Keep a reference to the manager, so we can keep going even
     after BackgroundHangManager::Shutdown is called. */
  const RefPtr<BackgroundHangManager> mManager;
  // Unique thread ID for identification
  const PRThread* mThreadID;

  void Update();

public:
  NS_INLINE_DECL_REFCOUNTING(BackgroundHangThread)
  /**
   * Returns the BackgroundHangThread associated with the
   * running thread. Note that this will not find private
   * BackgroundHangThread threads.
   *
   * @return BackgroundHangThread*, or nullptr if no thread
   *         is found.
   */
  static BackgroundHangThread* FindThread();

  static void Startup()
  {
    /* We can tolerate init() failing. */
    sTlsKeyInitialized = sTlsKey.init();
  }

  // Hang timeout in ticks
  const PRIntervalTime mTimeout;
  // PermaHang timeout in ticks
  const PRIntervalTime mMaxTimeout;
  // Time at last activity
  PRIntervalTime mInterval;
  // Time when a hang started
  PRIntervalTime mHangStart;
  // Is the thread in a hang
  bool mHanging;
  // Is the thread in a waiting state
  bool mWaiting;
  // Is the thread dedicated to a single BackgroundHangMonitor
  BackgroundHangMonitor::ThreadType mThreadType;
  // Annotations for the current hang
  UniquePtr<HangMonitor::HangAnnotations> mAnnotations;
  // Annotators registered for this thread
  HangMonitor::Observer::Annotators mAnnotators;

  BackgroundHangThread(const char* aName,
                       uint32_t aTimeoutMs,
                       uint32_t aMaxTimeoutMs,
                       BackgroundHangMonitor::ThreadType aThreadType = BackgroundHangMonitor::THREAD_SHARED);

  // Called by BackgroundHangMonitor::NotifyActivity
  void NotifyActivity()
  {
    MonitorAutoLock autoLock(mManager->mLock);
    Update();
  }
  // Called by BackgroundHangMonitor::NotifyWait
  void NotifyWait()
  {
    MonitorAutoLock autoLock(mManager->mLock);

    if (mWaiting) {
      return;
    }

    Update();
    mWaiting = true;
  }

  // Returns true if this thread is (or might be) shared between other
  // BackgroundHangMonitors for the monitored thread.
  bool IsShared() {
    return mThreadType == BackgroundHangMonitor::THREAD_SHARED;
  }
};


StaticRefPtr<BackgroundHangManager> BackgroundHangManager::sInstance;
bool BackgroundHangManager::sDisabled = false;

MOZ_THREAD_LOCAL(BackgroundHangThread*) BackgroundHangThread::sTlsKey;
bool BackgroundHangThread::sTlsKeyInitialized;

BackgroundHangManager::BackgroundHangManager()
  : mShutdown(false)
  , mLock("BackgroundHangManager")
  , mIntervalNow(0)
{
  // Lock so we don't race against the new monitor thread
  MonitorAutoLock autoLock(mLock);
  mHangMonitorThread = PR_CreateThread(
    PR_USER_THREAD, MonitorThread, this,
    PR_PRIORITY_LOW, PR_GLOBAL_THREAD, PR_JOINABLE_THREAD, 0);

  MOZ_ASSERT(mHangMonitorThread, "Failed to create monitor thread");
}

BackgroundHangManager::~BackgroundHangManager()
{
  MOZ_ASSERT(mShutdown, "Destruction without Shutdown call");
  MOZ_ASSERT(mHangThreads.isEmpty(), "Destruction with outstanding monitors");
  MOZ_ASSERT(mHangMonitorThread, "No monitor thread");

  // PR_CreateThread could have failed above due to resource limitation
  if (mHangMonitorThread) {
    // The monitor thread can only live as long as the instance lives
    PR_JoinThread(mHangMonitorThread);
  }
}

void
BackgroundHangManager::RunMonitorThread()
{
  // Keep us locked except when waiting
  MonitorAutoLock autoLock(mLock);

  /* mIntervalNow is updated at various intervals determined by waitTime.
     However, if an update latency is too long (due to CPU scheduling, system
     sleep, etc.), we don't update mIntervalNow at all. This is done so that
     long latencies in our timing are not detected as hangs. systemTime is
     used to track PR_IntervalNow() and determine our latency. */

  PRIntervalTime systemTime = PR_IntervalNow();
  // Default values for the first iteration of thread loop
  PRIntervalTime waitTime = PR_INTERVAL_NO_WAIT;
  PRIntervalTime recheckTimeout = PR_INTERVAL_NO_WAIT;

  while (!mShutdown) {

    PR_ClearInterrupt();
    nsresult rv = autoLock.Wait(waitTime);

    PRIntervalTime newTime = PR_IntervalNow();
    PRIntervalTime systemInterval = newTime - systemTime;
    systemTime = newTime;

    /* waitTime is a quarter of the shortest timeout value; If our timing
       latency is low enough (less than half the shortest timeout value),
       we can update mIntervalNow. */
    if (MOZ_LIKELY(waitTime != PR_INTERVAL_NO_TIMEOUT &&
                   systemInterval < 2 * waitTime)) {
      mIntervalNow += systemInterval;
    }

    /* If it's before the next recheck timeout, and our wait did not
       get interrupted (either through Notify or PR_Interrupt), we can
       keep the current waitTime and skip iterating through hang monitors. */
    if (MOZ_LIKELY(systemInterval < recheckTimeout &&
                   systemInterval >= waitTime &&
                   rv == NS_OK)) {
      recheckTimeout -= systemInterval;
      continue;
    }

    /* We are in one of the following scenarios,
     - Hang or permahang recheck timeout
     - Thread added/removed
     - Thread wait or hang ended
       In all cases, we want to go through our list of hang
       monitors and update waitTime and recheckTimeout. */
    waitTime = PR_INTERVAL_NO_TIMEOUT;
    recheckTimeout = PR_INTERVAL_NO_TIMEOUT;

    // Locally hold mIntervalNow
    PRIntervalTime intervalNow = mIntervalNow;

    // iterate through hang monitors
    for (BackgroundHangThread* currentThread = mHangThreads.getFirst();
         currentThread; currentThread = currentThread->getNext()) {

      if (currentThread->mWaiting) {
        // Thread is waiting, not hanging
        continue;
      }
      PRIntervalTime interval = currentThread->mInterval;
      PRIntervalTime hangTime = intervalNow - interval;
      if (MOZ_UNLIKELY(hangTime >= currentThread->mMaxTimeout)) {
        // A permahang started
        // Skip subsequent iterations and tolerate a race on mWaiting here
        currentThread->mWaiting = true;
        currentThread->mHanging = false;
        continue;
      }

      if (MOZ_LIKELY(!currentThread->mHanging)) {
        if (MOZ_UNLIKELY(hangTime >= currentThread->mTimeout)) {
          // A hang started
          currentThread->mHangStart = interval;
          currentThread->mHanging = true;
          currentThread->mAnnotations =
            currentThread->mAnnotators.GatherAnnotations();
        }
      } else {
        if (MOZ_LIKELY(interval != currentThread->mHangStart)) {
          // A hang ended
          currentThread->mHanging = false;
        }
      }

      /* If we are hanging, the next time we check for hang status is when
         the hang turns into a permahang. If we're not hanging, the next
         recheck timeout is when we may be entering a hang. */
      PRIntervalTime nextRecheck;
      if (currentThread->mHanging) {
        nextRecheck = currentThread->mMaxTimeout;
      } else {
        nextRecheck = currentThread->mTimeout;
      }
      recheckTimeout = std::min(recheckTimeout, nextRecheck - hangTime);

      if (currentThread->mTimeout != PR_INTERVAL_NO_TIMEOUT) {
        /* We wait for a quarter of the shortest timeout
           value to give mIntervalNow enough granularity. */
        waitTime = std::min(waitTime, currentThread->mTimeout / 4);
      }
    }
  }

  /* We are shutting down now.
     Wait for all outstanding monitors to unregister. */
  while (!mHangThreads.isEmpty()) {
    autoLock.Wait(PR_INTERVAL_NO_TIMEOUT);
  }
}


BackgroundHangThread::BackgroundHangThread(const char* aName,
                                           uint32_t aTimeoutMs,
                                           uint32_t aMaxTimeoutMs,
                                           BackgroundHangMonitor::ThreadType aThreadType)
  : mManager(BackgroundHangManager::sInstance)
  , mThreadID(PR_GetCurrentThread())
  , mTimeout(aTimeoutMs == BackgroundHangMonitor::kNoTimeout
             ? PR_INTERVAL_NO_TIMEOUT
             : PR_MillisecondsToInterval(aTimeoutMs))
  , mMaxTimeout(aMaxTimeoutMs == BackgroundHangMonitor::kNoTimeout
                ? PR_INTERVAL_NO_TIMEOUT
                : PR_MillisecondsToInterval(aMaxTimeoutMs))
  , mInterval(mManager->mIntervalNow)
  , mHangStart(mInterval)
  , mHanging(false)
  , mWaiting(true)
  , mThreadType(aThreadType)
{
  if (sTlsKeyInitialized && IsShared()) {
    sTlsKey.set(this);
  }
  // Lock here because LinkedList is not thread-safe
  MonitorAutoLock autoLock(mManager->mLock);
  // Add to thread list
  mManager->mHangThreads.insertBack(this);
  // Wake up monitor thread to process new thread
  autoLock.Notify();
}

BackgroundHangThread::~BackgroundHangThread()
{
  // Lock here because LinkedList is not thread-safe
  MonitorAutoLock autoLock(mManager->mLock);
  // Remove from thread list
  remove();
  // Wake up monitor thread to process removed thread
  autoLock.Notify();

  // We no longer have a thread
  if (sTlsKeyInitialized && IsShared()) {
    sTlsKey.set(nullptr);
  }
}

MOZ_ALWAYS_INLINE void
BackgroundHangThread::Update()
{
  PRIntervalTime intervalNow = mManager->mIntervalNow;
  if (mWaiting) {
    mInterval = intervalNow;
    mWaiting = false;
    /* We have to wake up the manager thread because when all threads
       are waiting, the manager thread waits indefinitely as well. */
    mManager->Wakeup();
  } else {
    PRIntervalTime duration = intervalNow - mInterval;
    if (MOZ_UNLIKELY(duration >= mTimeout)) {
      /* Wake up the manager thread to tell it that a hang ended */
      mManager->Wakeup();
    }
    mInterval = intervalNow;
  }
}

BackgroundHangThread*
BackgroundHangThread::FindThread()
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  if (BackgroundHangManager::sInstance == nullptr) {
    MOZ_ASSERT(BackgroundHangManager::sDisabled,
               "BackgroundHandleManager is not initialized");
    return nullptr;
  }

  if (sTlsKeyInitialized) {
    // Use TLS if available
    return sTlsKey.get();
  }
  // If TLS is unavailable, we can search through the thread list
  RefPtr<BackgroundHangManager> manager(BackgroundHangManager::sInstance);
  MOZ_ASSERT(manager, "Creating BackgroundHangMonitor after shutdown");

  PRThread* threadID = PR_GetCurrentThread();
  // Lock thread list for traversal
  MonitorAutoLock autoLock(manager->mLock);
  for (BackgroundHangThread* thread = manager->mHangThreads.getFirst();
       thread; thread = thread->getNext()) {
    if (thread->mThreadID == threadID && thread->IsShared()) {
      return thread;
    }
  }
#endif
  // Current thread is not initialized
  return nullptr;
}

bool
BackgroundHangMonitor::ShouldDisableOnBeta(const nsCString &clientID) {
  MOZ_ASSERT(clientID.Length() == 36, "clientID is invalid");
  const char *suffix = clientID.get() + clientID.Length() - 4;
  return strtol(suffix, NULL, 16) % BHR_BETA_MOD;
}

bool
BackgroundHangMonitor::IsDisabled() {
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  return BackgroundHangManager::sDisabled;
#else
  return true;
#endif
}

bool
BackgroundHangMonitor::DisableOnBeta() {
  if (XRE_IsParentProcess()) {
    BackgroundHangMonitor::Shutdown();
  } else {
    BackgroundHangManager::sDisabled = true;
  }
  return true;
}

void
BackgroundHangMonitor::Startup()
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  MOZ_ASSERT(!BackgroundHangManager::sInstance, "Already initialized");

  if (!strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "beta")) {
    if (XRE_IsParentProcess()) { // cached ClientID hasn't been read yet
      BackgroundHangThread::Startup();
      BackgroundHangManager::sInstance = new BackgroundHangManager();

      nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
      MOZ_ASSERT(observerService);

      observerService->AddObserver(BackgroundHangManager::sInstance, "profile-after-change", false);
      return;
    } else if(DisableOnBeta()){
      return;
    }
  }

  BackgroundHangThread::Startup();
  BackgroundHangManager::sInstance = new BackgroundHangManager();
#endif
}

void
BackgroundHangMonitor::Shutdown()
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  if (BackgroundHangManager::sDisabled) {
    MOZ_ASSERT(!BackgroundHangManager::sInstance, "Initialized");
    return;
  }

  MOZ_ASSERT(BackgroundHangManager::sInstance, "Not initialized");
  /* Scope our lock inside Shutdown() because the sInstance object can
     be destroyed as soon as we set sInstance to nullptr below, and
     we don't want to hold the lock when it's being destroyed. */
  BackgroundHangManager::sInstance->Shutdown();
  BackgroundHangManager::sInstance = nullptr;
  BackgroundHangManager::sDisabled = true;
#endif
}

BackgroundHangMonitor::BackgroundHangMonitor(const char* aName,
                                             uint32_t aTimeoutMs,
                                             uint32_t aMaxTimeoutMs,
                                             ThreadType aThreadType)
  : mThread(aThreadType == THREAD_SHARED ? BackgroundHangThread::FindThread() : nullptr)
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  if (!BackgroundHangManager::sDisabled && !mThread) {
    mThread = new BackgroundHangThread(aName, aTimeoutMs, aMaxTimeoutMs,
                                       aThreadType);
  }
#endif
}

BackgroundHangMonitor::BackgroundHangMonitor()
  : mThread(BackgroundHangThread::FindThread())
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  if (BackgroundHangManager::sDisabled) {
    return;
  }
#endif
}

BackgroundHangMonitor::~BackgroundHangMonitor()
{
}

void
BackgroundHangMonitor::NotifyActivity()
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  if (mThread == nullptr) {
    MOZ_ASSERT(BackgroundHangManager::sDisabled,
               "This thread is not initialized for hang monitoring");
    return;
  }
#endif
// STUB
}

void
BackgroundHangMonitor::NotifyWait()
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  if (mThread == nullptr) {
    MOZ_ASSERT(BackgroundHangManager::sDisabled,
               "This thread is not initialized for hang monitoring");
    return;
  }
#endif
// STUB
}

bool
BackgroundHangMonitor::RegisterAnnotator(HangMonitor::Annotator& aAnnotator)
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  BackgroundHangThread* thisThread = BackgroundHangThread::FindThread();
  if (!thisThread) {
    return false;
  }
  return thisThread->mAnnotators.Register(aAnnotator);
#else
  return false;
#endif
}

bool
BackgroundHangMonitor::UnregisterAnnotator(HangMonitor::Annotator& aAnnotator)
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  BackgroundHangThread* thisThread = BackgroundHangThread::FindThread();
  if (!thisThread) {
    return false;
  }
  return thisThread->mAnnotators.Unregister(aAnnotator);
#else
  return false;
#endif
}

/* Because we are iterating through the BackgroundHangThread linked list,
   we need to take a lock. Using MonitorAutoLock as a base class makes
   sure all of that is taken care of for us. */
BackgroundHangMonitor::ThreadHangStatsIterator::ThreadHangStatsIterator()
  : MonitorAutoLock(BackgroundHangManager::sInstance->mLock)
  , mThread(BackgroundHangManager::sInstance ?
            BackgroundHangManager::sInstance->mHangThreads.getFirst() :
            nullptr)
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
  MOZ_ASSERT(BackgroundHangManager::sInstance ||
             BackgroundHangManager::sDisabled,
             "Inconsistent state");
#endif
}

} // namespace mozilla