Revision control

Line Code
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
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
/* 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 "CacheIOThread.h"
#include "CacheFileIOManager.h"

#include "nsIRunnable.h"
#include "nsISupportsImpl.h"
#include "nsPrintfCString.h"
#include "nsThreadUtils.h"
#include "mozilla/IOInterposer.h"
#include "GeckoProfiler.h"

#ifdef XP_WIN
#include <windows.h>
#endif

#ifdef MOZ_TASK_TRACER
#include "GeckoTaskTracer.h"
#include "TracedTaskCommon.h"
#endif

namespace mozilla {
namespace net {

namespace { // anon

class CacheIOTelemetry
{
public:
  typedef CacheIOThread::EventQueue::size_type size_type;
  static size_type mMinLengthToReport[CacheIOThread::LAST_LEVEL];
  static void Report(uint32_t aLevel, size_type aLength);
};

static CacheIOTelemetry::size_type const kGranularity = 30;

CacheIOTelemetry::size_type
CacheIOTelemetry::mMinLengthToReport[CacheIOThread::LAST_LEVEL] = {
  kGranularity, kGranularity, kGranularity, kGranularity,
  kGranularity, kGranularity, kGranularity, kGranularity
};

// static
void CacheIOTelemetry::Report(uint32_t aLevel, CacheIOTelemetry::size_type aLength)
{
  if (mMinLengthToReport[aLevel] > aLength) {
    return;
  }

  static Telemetry::HistogramID telemetryID[] = {
    Telemetry::HTTP_CACHE_IO_QUEUE_2_OPEN_PRIORITY,
    Telemetry::HTTP_CACHE_IO_QUEUE_2_READ_PRIORITY,
    Telemetry::HTTP_CACHE_IO_QUEUE_2_MANAGEMENT,
    Telemetry::HTTP_CACHE_IO_QUEUE_2_OPEN,
    Telemetry::HTTP_CACHE_IO_QUEUE_2_READ,
    Telemetry::HTTP_CACHE_IO_QUEUE_2_WRITE_PRIORITY,
    Telemetry::HTTP_CACHE_IO_QUEUE_2_WRITE,
    Telemetry::HTTP_CACHE_IO_QUEUE_2_INDEX,
    Telemetry::HTTP_CACHE_IO_QUEUE_2_EVICT
  };

  // Each bucket is a multiply of kGranularity (30, 60, 90..., 300+)
  aLength = (aLength / kGranularity);
  // Next time report only when over the current length + kGranularity
  mMinLengthToReport[aLevel] = (aLength + 1) * kGranularity;

  // 10 is number of buckets we have in each probe
  aLength = std::min<size_type>(aLength, 10);

  Telemetry::Accumulate(telemetryID[aLevel], aLength - 1); // counted from 0
}

} // anon

namespace detail {

/**
 * Helper class encapsulating platform-specific code to cancel
 * any pending IO operation taking too long.  Solely used during
 * shutdown to prevent any IO shutdown hangs.
 * Mainly designed for using Win32 CancelSynchronousIo function.
 */
class BlockingIOWatcher
{
#ifdef XP_WIN
  typedef BOOL(WINAPI* TCancelSynchronousIo)(HANDLE hThread);
  TCancelSynchronousIo mCancelSynchronousIo;
  // The native handle to the thread
  HANDLE mThread;
  // Event signaling back to the main thread, see NotifyOperationDone.
  HANDLE mEvent;
#endif

public:
  // Created and destroyed on the main thread only
  BlockingIOWatcher();
  ~BlockingIOWatcher();

  // Called on the IO thread to grab the platform specific
  // reference to it.
  void InitThread();
  // If there is a blocking operation being handled on the IO
  // thread, this is called on the main thread during shutdown.
  // Waits for notification from the IO thread for up to two seconds.
  // If that times out, it attempts to cancel the IO operation.
  void WatchAndCancel(Monitor& aMonitor);
  // Called by the IO thread after each operation has been
  // finished (after each Run() call).  This wakes the main
  // thread up and makes WatchAndCancel() early exit and become
  // a no-op.
  void NotifyOperationDone();
};

#ifdef XP_WIN

BlockingIOWatcher::BlockingIOWatcher()
  : mCancelSynchronousIo(NULL)
  , mThread(NULL)
  , mEvent(NULL)
{
  HMODULE kernel32_dll = GetModuleHandle("kernel32.dll");
  if (!kernel32_dll) {
    return;
  }

  FARPROC ptr = GetProcAddress(kernel32_dll, "CancelSynchronousIo");
  if (!ptr) {
    return;
  }

  mCancelSynchronousIo = reinterpret_cast<TCancelSynchronousIo>(ptr);

  mEvent = ::CreateEvent(NULL, TRUE, FALSE, NULL);
}

BlockingIOWatcher::~BlockingIOWatcher()
{
  if (mEvent) {
    CloseHandle(mEvent);
  }
  if (mThread) {
    CloseHandle(mThread);
  }
}

void BlockingIOWatcher::InitThread()
{
  // GetCurrentThread() only returns a pseudo handle, hence DuplicateHandle
  ::DuplicateHandle(
    GetCurrentProcess(),
    GetCurrentThread(),
    GetCurrentProcess(),
    &mThread,
    0,
    FALSE,
    DUPLICATE_SAME_ACCESS);
}

void BlockingIOWatcher::WatchAndCancel(Monitor& aMonitor)
{
  if (!mEvent) {
    return;
  }

  // Reset before we enter the monitor to raise the chance we catch
  // the currently pending IO op completion.
  ::ResetEvent(mEvent);

  HANDLE thread;
  {
    MonitorAutoLock lock(aMonitor);
    thread = mThread;

    if (!thread) {
      return;
    }
  }

  LOG(("Blocking IO operation pending on IO thread, waiting..."));

  // It seems wise to use the I/O lag time as a maximum time to wait
  // for an operation to finish.  When that times out and cancelation
  // succeeds, there will be no other IO operation permitted.  By default
  // this is two seconds.
  uint32_t maxLag = std::min<uint32_t>(5, CacheObserver::MaxShutdownIOLag()) * 1000;

  DWORD result = ::WaitForSingleObject(mEvent, maxLag);
  if (result == WAIT_TIMEOUT) {
    LOG(("CacheIOThread: Attempting to cancel a long blocking IO operation"));
    BOOL result = mCancelSynchronousIo(thread);
    if (result) {
      LOG(("  cancelation signal succeeded"));
    } else {
      DWORD error = GetLastError();
      LOG(("  cancelation signal failed with GetLastError=%u", error));
    }
  }
}

void BlockingIOWatcher::NotifyOperationDone()
{
  if (mEvent) {
    ::SetEvent(mEvent);
  }
}

#else // WIN

// Stub code only (we don't implement IO cancelation for this platform)

BlockingIOWatcher::BlockingIOWatcher() { }
BlockingIOWatcher::~BlockingIOWatcher() { }
void BlockingIOWatcher::InitThread() { }
void BlockingIOWatcher::WatchAndCancel(Monitor&) { }
void BlockingIOWatcher::NotifyOperationDone() { }

#endif

} // detail

CacheIOThread* CacheIOThread::sSelf = nullptr;

NS_IMPL_ISUPPORTS(CacheIOThread, nsIThreadObserver)

CacheIOThread::CacheIOThread()
: mMonitor("CacheIOThread")
, mThread(nullptr)
, mXPCOMThread(nullptr)
, mLowestLevelWaiting(LAST_LEVEL)
, mCurrentlyExecutingLevel(0)
, mHasXPCOMEvents(false)
, mRerunCurrentEvent(false)
, mShutdown(false)
, mIOCancelableEvents(0)
, mEventCounter(0)
#ifdef DEBUG
, mInsideLoop(true)
#endif
{
  for (uint32_t i = 0; i < LAST_LEVEL; ++i) {
    mQueueLength[i] = 0;
  }

  sSelf = this;
}

CacheIOThread::~CacheIOThread()
{
  if (mXPCOMThread) {
    nsIThread *thread = mXPCOMThread;
    thread->Release();
  }

  sSelf = nullptr;
#ifdef DEBUG
  for (uint32_t level = 0; level < LAST_LEVEL; ++level) {
    MOZ_ASSERT(!mEventQueue[level].Length());
  }
#endif
}

nsresult CacheIOThread::Init()
{
  {
    MonitorAutoLock lock(mMonitor);
    // Yeah, there is not a thread yet, but we want to make sure
    // the sequencing is correct.
    mBlockingIOWatcher = MakeUnique<detail::BlockingIOWatcher>();
  }

  mThread = PR_CreateThread(PR_USER_THREAD, ThreadFunc, this,
                            PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD,
                            PR_JOINABLE_THREAD, 128 * 1024);
  if (!mThread) {
    return NS_ERROR_FAILURE;
  }

  return NS_OK;
}

nsresult CacheIOThread::Dispatch(nsIRunnable* aRunnable, uint32_t aLevel)
{
  return Dispatch(do_AddRef(aRunnable), aLevel);
}

nsresult CacheIOThread::Dispatch(already_AddRefed<nsIRunnable> aRunnable,
				 uint32_t aLevel)
{
  NS_ENSURE_ARG(aLevel < LAST_LEVEL);

  nsCOMPtr<nsIRunnable> runnable(aRunnable);

  // Runnable is always expected to be non-null, hard null-check bellow.
  MOZ_ASSERT(runnable);

  MonitorAutoLock lock(mMonitor);

  if (mShutdown && (PR_GetCurrentThread() != mThread))
    return NS_ERROR_UNEXPECTED;

  return DispatchInternal(runnable.forget(), aLevel);
}

nsresult CacheIOThread::DispatchAfterPendingOpens(nsIRunnable* aRunnable)
{
  // Runnable is always expected to be non-null, hard null-check bellow.
  MOZ_ASSERT(aRunnable);

  MonitorAutoLock lock(mMonitor);

  if (mShutdown && (PR_GetCurrentThread() != mThread))
    return NS_ERROR_UNEXPECTED;

  // Move everything from later executed OPEN level to the OPEN_PRIORITY level
  // where we post the (eviction) runnable.
  mQueueLength[OPEN_PRIORITY] += mEventQueue[OPEN].Length();
  mQueueLength[OPEN] -= mEventQueue[OPEN].Length();
  mEventQueue[OPEN_PRIORITY].AppendElements(mEventQueue[OPEN]);
  mEventQueue[OPEN].Clear();

  return DispatchInternal(do_AddRef(aRunnable), OPEN_PRIORITY);
}

nsresult CacheIOThread::DispatchInternal(already_AddRefed<nsIRunnable> aRunnable,
					 uint32_t aLevel)
{
  nsCOMPtr<nsIRunnable> runnable(aRunnable);
#ifdef MOZ_TASK_TRACER
  if (tasktracer::IsStartLogging()) {
      runnable = tasktracer::CreateTracedRunnable(runnable.forget());
      (static_cast<tasktracer::TracedRunnable*>(runnable.get()))->DispatchTask();
  }
#endif

  if (NS_WARN_IF(!runnable))
    return NS_ERROR_NULL_POINTER;

  mMonitor.AssertCurrentThreadOwns();

  ++mQueueLength[aLevel];
  mEventQueue[aLevel].AppendElement(runnable.forget());
  if (mLowestLevelWaiting > aLevel)
    mLowestLevelWaiting = aLevel;

  mMonitor.NotifyAll();

  return NS_OK;
}

bool CacheIOThread::IsCurrentThread()
{
  return mThread == PR_GetCurrentThread();
}

uint32_t CacheIOThread::QueueSize(bool highPriority)
{
  MonitorAutoLock lock(mMonitor);
  if (highPriority) {
    return mQueueLength[OPEN_PRIORITY] + mQueueLength[READ_PRIORITY];
  }

  return mQueueLength[OPEN_PRIORITY] + mQueueLength[READ_PRIORITY] +
         mQueueLength[MANAGEMENT] + mQueueLength[OPEN] + mQueueLength[READ];
}

bool CacheIOThread::YieldInternal()
{
  if (!IsCurrentThread()) {
    NS_WARNING("Trying to yield to priority events on non-cache2 I/O thread? "
               "You probably do something wrong.");
    return false;
  }

  if (mCurrentlyExecutingLevel == XPCOM_LEVEL) {
    // Doesn't make any sense, since this handler is the one
    // that would be executed as the next one.
    return false;
  }

  if (!EventsPending(mCurrentlyExecutingLevel))
    return false;

  mRerunCurrentEvent = true;
  return true;
}

void CacheIOThread::Shutdown()
{
  if (!mThread) {
    return;
  }

  {
    MonitorAutoLock lock(mMonitor);
    mShutdown = true;
    mMonitor.NotifyAll();
  }

  PR_JoinThread(mThread);
  mThread = nullptr;
}

void CacheIOThread::CancelBlockingIO()
{
  // This is an attempt to cancel any blocking I/O operation taking
  // too long time.
  if (!mBlockingIOWatcher) {
    return;
  }

  if (!mIOCancelableEvents) {
    LOG(("CacheIOThread::CancelBlockingIO, no blocking operation to cancel"));
    return;
  }

  // OK, when we are here, we are processing an IO on the thread that
  // can be cancelled.
  mBlockingIOWatcher->WatchAndCancel(mMonitor);
}

already_AddRefed<nsIEventTarget> CacheIOThread::Target()
{
  nsCOMPtr<nsIEventTarget> target;

  target = mXPCOMThread;
  if (!target && mThread)
  {
    MonitorAutoLock lock(mMonitor);
    while (!mXPCOMThread) {
      lock.Wait();
    }

    target = mXPCOMThread;
  }

  return target.forget();
}

// static
void CacheIOThread::ThreadFunc(void* aClosure)
{
  // XXXmstange We'd like to register this thread with the profiler, but doing
  // so causes leaks, see bug 1323100.
  NS_SetCurrentThreadName("Cache2 I/O");

  mozilla::IOInterposer::RegisterCurrentThread();
  CacheIOThread* thread = static_cast<CacheIOThread*>(aClosure);
  thread->ThreadFunc();
  mozilla::IOInterposer::UnregisterCurrentThread();
}

void CacheIOThread::ThreadFunc()
{
  nsCOMPtr<nsIThreadInternal> threadInternal;

  {
    MonitorAutoLock lock(mMonitor);

    MOZ_ASSERT(mBlockingIOWatcher);
    mBlockingIOWatcher->InitThread();

    // This creates nsThread for this PRThread
    nsCOMPtr<nsIThread> xpcomThread = NS_GetCurrentThread();

    threadInternal = do_QueryInterface(xpcomThread);
    if (threadInternal)
      threadInternal->SetObserver(this);

    mXPCOMThread = xpcomThread.forget().take();

    lock.NotifyAll();

    do {
loopStart:
      // Reset the lowest level now, so that we can detect a new event on
      // a lower level (i.e. higher priority) has been scheduled while
      // executing any previously scheduled event.
      mLowestLevelWaiting = LAST_LEVEL;

      // Process xpcom events first
      while (mHasXPCOMEvents) {
        mHasXPCOMEvents = false;
        mCurrentlyExecutingLevel = XPCOM_LEVEL;

        MonitorAutoUnlock unlock(mMonitor);

        bool processedEvent;
        nsresult rv;
        do {
          nsIThread *thread = mXPCOMThread;
          rv = thread->ProcessNextEvent(false, &processedEvent);

          ++mEventCounter;
          MOZ_ASSERT(mBlockingIOWatcher);
          mBlockingIOWatcher->NotifyOperationDone();
        } while (NS_SUCCEEDED(rv) && processedEvent);
      }

      uint32_t level;
      for (level = 0; level < LAST_LEVEL; ++level) {
        if (!mEventQueue[level].Length()) {
          // no events on this level, go to the next level
          continue;
        }

        LoopOneLevel(level);

        // Go to the first (lowest) level again
        goto loopStart;
      }

      if (EventsPending()) {
        continue;
      }

      if (mShutdown) {
        break;
      }

      lock.Wait(PR_INTERVAL_NO_TIMEOUT);

    } while (true);

    MOZ_ASSERT(!EventsPending());

#ifdef DEBUG
    // This is for correct assertion on XPCOM events dispatch.
    mInsideLoop = false;
#endif
  } // lock

  if (threadInternal)
    threadInternal->SetObserver(nullptr);
}

void CacheIOThread::LoopOneLevel(uint32_t aLevel)
{
  EventQueue events;
  events.SwapElements(mEventQueue[aLevel]);
  EventQueue::size_type length = events.Length();

  mCurrentlyExecutingLevel = aLevel;

  bool returnEvents = false;
  bool reportTelemetry = true;

  EventQueue::size_type index;
  {
    MonitorAutoUnlock unlock(mMonitor);

    for (index = 0; index < length; ++index) {
      if (EventsPending(aLevel)) {
        // Somebody scheduled a new event on a lower level, break and harry
        // to execute it!  Don't forget to return what we haven't exec.
        returnEvents = true;
        break;
      }

      if (reportTelemetry) {
        reportTelemetry = false;
        CacheIOTelemetry::Report(aLevel, length);
      }

      // Drop any previous flagging, only an event on the current level may set
      // this flag.
      mRerunCurrentEvent = false;

      events[index]->Run();

      MOZ_ASSERT(mBlockingIOWatcher);
      mBlockingIOWatcher->NotifyOperationDone();

      if (mRerunCurrentEvent) {
        // The event handler yields to higher priority events and wants to rerun.
        returnEvents = true;
        break;
      }

      ++mEventCounter;
      --mQueueLength[aLevel];

      // Release outside the lock.
      events[index] = nullptr;
    }
  }

  if (returnEvents)
    mEventQueue[aLevel].InsertElementsAt(0, events.Elements() + index, length - index);
}

bool CacheIOThread::EventsPending(uint32_t aLastLevel)
{
  return mLowestLevelWaiting < aLastLevel || mHasXPCOMEvents;
}

NS_IMETHODIMP CacheIOThread::OnDispatchedEvent()
{
  MonitorAutoLock lock(mMonitor);
  mHasXPCOMEvents = true;
  MOZ_ASSERT(mInsideLoop);
  lock.Notify();
  return NS_OK;
}

NS_IMETHODIMP CacheIOThread::OnProcessNextEvent(nsIThreadInternal *thread, bool mayWait)
{
  return NS_OK;
}

NS_IMETHODIMP CacheIOThread::AfterProcessNextEvent(nsIThreadInternal *thread,
                                                   bool eventWasProcessed)
{
  return NS_OK;
}

// Memory reporting

size_t CacheIOThread::SizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const
{
  MonitorAutoLock lock(const_cast<CacheIOThread*>(this)->mMonitor);

  size_t n = 0;
  n += mallocSizeOf(mThread);
  for (uint32_t level = 0; level < LAST_LEVEL; ++level) {
    n += mEventQueue[level].ShallowSizeOfExcludingThis(mallocSizeOf);
    // Events referenced by the queues are arbitrary objects we cannot be sure
    // are reported elsewhere as well as probably not implementing nsISizeOf
    // interface.  Deliberatly omitting them from reporting here.
  }

  return n;
}

size_t CacheIOThread::SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const
{
  return mallocSizeOf(this) + SizeOfExcludingThis(mallocSizeOf);
}

CacheIOThread::Cancelable::Cancelable(bool aCancelable)
  : mCancelable(aCancelable)
{
  // This will only ever be used on the I/O thread,
  // which is expected to be alive longer than this class.
  MOZ_ASSERT(CacheIOThread::sSelf);
  MOZ_ASSERT(CacheIOThread::sSelf->IsCurrentThread());

  if (mCancelable) {
    ++CacheIOThread::sSelf->mIOCancelableEvents;
  }
}

CacheIOThread::Cancelable::~Cancelable()
{
  MOZ_ASSERT(CacheIOThread::sSelf);

  if (mCancelable) {
    --CacheIOThread::sSelf->mIOCancelableEvents;
  }
}

} // namespace net
} // namespace mozilla