DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (409f3966645a)

VCS Links

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
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 "PrioritizedEventQueue.h"
#include "mozilla/EventQueue.h"
#include "mozilla/ScopeExit.h"
#include "nsThreadManager.h"
#include "nsXPCOMPrivate.h" // for gXPCOMThreadsShutDown
#include "InputEventStatistics.h"

using namespace mozilla;

template<class InnerQueueT>
PrioritizedEventQueue<InnerQueueT>::PrioritizedEventQueue(UniquePtr<InnerQueueT> aHighQueue,
                                                          UniquePtr<InnerQueueT> aInputQueue,
                                                          UniquePtr<InnerQueueT> aNormalQueue,
                                                          UniquePtr<InnerQueueT> aIdleQueue,
                                                          already_AddRefed<nsIIdlePeriod> aIdlePeriod)
  : mHighQueue(std::move(aHighQueue))
  , mInputQueue(std::move(aInputQueue))
  , mNormalQueue(std::move(aNormalQueue))
  , mIdleQueue(std::move(aIdleQueue))
  , mIdlePeriod(aIdlePeriod)
{
  static_assert(IsBaseOf<AbstractEventQueue, InnerQueueT>::value,
                "InnerQueueT must be an AbstractEventQueue subclass");
}

template<class InnerQueueT>
void
PrioritizedEventQueue<InnerQueueT>::PutEvent(already_AddRefed<nsIRunnable>&& aEvent,
                                             EventPriority aPriority,
                                             const MutexAutoLock& aProofOfLock)
{
  // Double check the priority with a QI.
  RefPtr<nsIRunnable> event(aEvent);
  EventPriority priority = aPriority;

  if (priority == EventPriority::Input && mInputQueueState == STATE_DISABLED) {
    priority = EventPriority::Normal;
  }

  switch (priority) {
  case EventPriority::High:
    mHighQueue->PutEvent(event.forget(), priority, aProofOfLock);
    break;
  case EventPriority::Input:
    mInputQueue->PutEvent(event.forget(), priority, aProofOfLock);
    break;
  case EventPriority::Normal:
    mNormalQueue->PutEvent(event.forget(), priority, aProofOfLock);
    break;
  case EventPriority::Idle:
    mIdleQueue->PutEvent(event.forget(), priority, aProofOfLock);
    break;
  case EventPriority::Count:
    MOZ_CRASH("EventPriority::Count isn't a valid priority");
    break;
  }
}

template<class InnerQueueT>
TimeStamp
PrioritizedEventQueue<InnerQueueT>::GetIdleDeadline()
{
  // If we are shutting down, we won't honor the idle period, and we will
  // always process idle runnables.  This will ensure that the idle queue
  // gets exhausted at shutdown time to prevent intermittently leaking
  // some runnables inside that queue and even worse potentially leaving
  // some important cleanup work unfinished.
  if (gXPCOMThreadsShutDown || nsThreadManager::get().GetCurrentThread()->ShuttingDown()) {
    return TimeStamp::Now();
  }

  TimeStamp idleDeadline;
  {
    // Releasing the lock temporarily since getting the idle period
    // might need to lock the timer thread. Unlocking here might make
    // us receive an event on the main queue, but we've committed to
    // run an idle event anyhow.
    MutexAutoUnlock unlock(*mMutex);
    mIdlePeriod->GetIdlePeriodHint(&idleDeadline);
  }

  // If HasPendingEvents() has been called and it has returned true because of
  // pending idle events, there is a risk that we may decide here that we aren't
  // idle and return null, in which case HasPendingEvents() has effectively
  // lied.  Since we can't go back and fix the past, we have to adjust what we
  // do here and forcefully pick the idle queue task here.  Note that this means
  // that we are choosing to run a task from the idle queue when we would
  // normally decide that we aren't in an idle period, but this can only happen
  // if we fall out of the idle period in between the call to HasPendingEvents()
  // and here, which should hopefully be quite rare.  We are effectively
  // choosing to prioritize the sanity of our API semantics over the optimal
  // scheduling.
  if (!mHasPendingEventsPromisedIdleEvent &&
      (!idleDeadline || idleDeadline < TimeStamp::Now())) {
    return TimeStamp();
  }
  if (mHasPendingEventsPromisedIdleEvent && !idleDeadline) {
    // If HasPendingEvents() has been called and it has returned true, but we're no
    // longer in the idle period, we must return a valid timestamp to pretend that
    // we are still in the idle period.
    return TimeStamp::Now();
  }
  return idleDeadline;
}

template<class InnerQueueT>
EventPriority
PrioritizedEventQueue<InnerQueueT>::SelectQueue(bool aUpdateState,
                                                const MutexAutoLock& aProofOfLock)
{
  bool highPending = !mHighQueue->IsEmpty(aProofOfLock);
  bool normalPending = !mNormalQueue->IsEmpty(aProofOfLock);
  size_t inputCount = mInputQueue->Count(aProofOfLock);

  if (aUpdateState &&
      mInputQueueState == STATE_ENABLED &&
      mInputHandlingStartTime.IsNull() &&
      inputCount > 0) {
    mInputHandlingStartTime =
      InputEventStatistics::Get()
      .GetInputHandlingStartTime(inputCount);
  }

  // We check the different queues in the following order. The conditions we use
  // are meant to avoid starvation and to ensure that we don't process an event
  // at the wrong time.
  //
  // HIGH: if mProcessHighPriorityQueue
  // INPUT: if inputCount > 0 && TimeStamp::Now() > mInputHandlingStartTime
  // NORMAL: if normalPending
  //
  // If we still don't have an event, then we take events from the queues
  // in the following order:
  //
  // HIGH
  // INPUT
  // IDLE: if GetIdleDeadline()
  //
  // If we don't get an event in this pass, then we return null since no events
  // are ready.

  // This variable determines which queue we will take an event from.
  EventPriority queue;

  if (mProcessHighPriorityQueue) {
    queue = EventPriority::High;
  } else if (inputCount > 0 && (mInputQueueState == STATE_FLUSHING ||
                                (mInputQueueState == STATE_ENABLED &&
                                 !mInputHandlingStartTime.IsNull() &&
                                 TimeStamp::Now() > mInputHandlingStartTime))) {
    queue = EventPriority::Input;
  } else if (normalPending) {
    MOZ_ASSERT(mInputQueueState != STATE_FLUSHING,
               "Shouldn't consume normal event when flusing input events");
    queue = EventPriority::Normal;
  } else if (highPending) {
    queue = EventPriority::High;
  } else if (inputCount > 0 && mInputQueueState != STATE_SUSPEND) {
    MOZ_ASSERT(mInputQueueState != STATE_DISABLED,
               "Shouldn't consume input events when the input queue is disabled");
    queue = EventPriority::Input;
  } else {
    // We may not actually return an idle event in this case.
    queue = EventPriority::Idle;
  }

  MOZ_ASSERT_IF(queue == EventPriority::Input,
                mInputQueueState != STATE_DISABLED && mInputQueueState != STATE_SUSPEND);

  if (aUpdateState) {
    mProcessHighPriorityQueue = highPending;
  }

  return queue;
}

template<class InnerQueueT>
already_AddRefed<nsIRunnable>
PrioritizedEventQueue<InnerQueueT>::GetEvent(EventPriority* aPriority,
                                             const MutexAutoLock& aProofOfLock)
{
  auto guard = MakeScopeExit([&] {
    mHasPendingEventsPromisedIdleEvent = false;
  });

#ifndef RELEASE_OR_BETA
  // Clear mNextIdleDeadline so that it is possible to determine that
  // we're running an idle runnable in ProcessNextEvent.
  *mNextIdleDeadline = TimeStamp();
#endif

  EventPriority queue = SelectQueue(true, aProofOfLock);

  if (aPriority) {
    *aPriority = queue;
  }

  if (queue == EventPriority::High) {
    nsCOMPtr<nsIRunnable> event = mHighQueue->GetEvent(aPriority, aProofOfLock);
    MOZ_ASSERT(event);
    mInputHandlingStartTime = TimeStamp();
    mProcessHighPriorityQueue = false;
    return event.forget();
  }

  if (queue == EventPriority::Input) {
    nsCOMPtr<nsIRunnable> event = mInputQueue->GetEvent(aPriority, aProofOfLock);
    MOZ_ASSERT(event);
    return event.forget();
  }

  if (queue == EventPriority::Normal) {
    nsCOMPtr<nsIRunnable> event = mNormalQueue->GetEvent(aPriority, aProofOfLock);
    return event.forget();
  }

  // If we get here, then all queues except idle are empty.
  MOZ_ASSERT(queue == EventPriority::Idle);

  if (mIdleQueue->IsEmpty(aProofOfLock)) {
    MOZ_ASSERT(!mHasPendingEventsPromisedIdleEvent);
    return nullptr;
  }

  TimeStamp idleDeadline = GetIdleDeadline();
  if (!idleDeadline) {
    return nullptr;
  }

  nsCOMPtr<nsIRunnable> event = mIdleQueue->GetEvent(aPriority, aProofOfLock);
  if (event) {
    nsCOMPtr<nsIIdleRunnable> idleEvent = do_QueryInterface(event);
    if (idleEvent) {
      idleEvent->SetDeadline(idleDeadline);
    }

#ifndef RELEASE_OR_BETA
    // Store the next idle deadline to be able to determine budget use
    // in ProcessNextEvent.
    *mNextIdleDeadline = idleDeadline;
#endif
  }

  return event.forget();
}

template<class InnerQueueT>
bool
PrioritizedEventQueue<InnerQueueT>::IsEmpty(const MutexAutoLock& aProofOfLock)
{
  // Just check IsEmpty() on the sub-queues. Don't bother checking the idle
  // deadline since that only determines whether an idle event is ready or not.
  return mHighQueue->IsEmpty(aProofOfLock)
      && mInputQueue->IsEmpty(aProofOfLock)
      && mNormalQueue->IsEmpty(aProofOfLock)
      && mIdleQueue->IsEmpty(aProofOfLock);
}

template<class InnerQueueT>
bool
PrioritizedEventQueue<InnerQueueT>::HasReadyEvent(const MutexAutoLock& aProofOfLock)
{
  mHasPendingEventsPromisedIdleEvent = false;

  EventPriority queue = SelectQueue(false, aProofOfLock);

  if (queue == EventPriority::High) {
    return mHighQueue->HasReadyEvent(aProofOfLock);
  } else if (queue == EventPriority::Input) {
    return mInputQueue->HasReadyEvent(aProofOfLock);
  } else if (queue == EventPriority::Normal) {
    return mNormalQueue->HasReadyEvent(aProofOfLock);
  }

  MOZ_ASSERT(queue == EventPriority::Idle);

  // If we get here, then both the high and normal queues are empty.

  if (mIdleQueue->IsEmpty(aProofOfLock)) {
    return false;
  }

  TimeStamp idleDeadline = GetIdleDeadline();
  if (idleDeadline && mIdleQueue->HasReadyEvent(aProofOfLock)) {
    mHasPendingEventsPromisedIdleEvent = true;
    return true;
  }

  return false;
}

template<class InnerQueueT>
size_t
PrioritizedEventQueue<InnerQueueT>::Count(const MutexAutoLock& aProofOfLock) const
{
  MOZ_CRASH("unimplemented");
}

template<class InnerQueueT>
void
PrioritizedEventQueue<InnerQueueT>::EnableInputEventPrioritization(const MutexAutoLock& aProofOfLock)
{
  MOZ_ASSERT(mInputQueueState == STATE_DISABLED);
  mInputQueueState = STATE_ENABLED;
  mInputHandlingStartTime = TimeStamp();
}

template<class InnerQueueT>
void
PrioritizedEventQueue<InnerQueueT>::
FlushInputEventPrioritization(const MutexAutoLock& aProofOfLock)
{
  MOZ_ASSERT(mInputQueueState == STATE_ENABLED || mInputQueueState == STATE_SUSPEND);
  mInputQueueState =
    mInputQueueState == STATE_ENABLED ? STATE_FLUSHING : STATE_SUSPEND;
}

template<class InnerQueueT>
void
PrioritizedEventQueue<InnerQueueT>::
SuspendInputEventPrioritization(const MutexAutoLock& aProofOfLock)
{
  MOZ_ASSERT(mInputQueueState == STATE_ENABLED || mInputQueueState == STATE_FLUSHING);
  mInputQueueState = STATE_SUSPEND;
}

template<class InnerQueueT>
void
PrioritizedEventQueue<InnerQueueT>::
ResumeInputEventPrioritization(const MutexAutoLock& aProofOfLock)
{
  MOZ_ASSERT(mInputQueueState == STATE_SUSPEND);
  mInputQueueState = STATE_ENABLED;
}

namespace mozilla {
template class PrioritizedEventQueue<EventQueue>;
template class PrioritizedEventQueue<LabeledEventQueue>;
}