mirror of
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147 lines
3.7 KiB
C++
147 lines
3.7 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "nsEventQueue.h"
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#include "nsAutoPtr.h"
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#include "mozilla/Logging.h"
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#include "nsThreadUtils.h"
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#include "prthread.h"
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#include "mozilla/ChaosMode.h"
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using namespace mozilla;
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static LazyLogModule sEventQueueLog("nsEventQueue");
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#ifdef LOG
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#undef LOG
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#endif
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#define LOG(args) MOZ_LOG(sEventQueueLog, mozilla::LogLevel::Debug, args)
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nsEventQueue::nsEventQueue(Mutex& aLock)
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: mHead(nullptr)
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, mTail(nullptr)
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, mOffsetHead(0)
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, mOffsetTail(0)
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, mEventsAvailable(aLock, "[nsEventQueue.mEventsAvailable]")
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{
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}
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nsEventQueue::~nsEventQueue()
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{
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// It'd be nice to be able to assert that no one else is holding the lock,
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// but NSPR doesn't really expose APIs for it.
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NS_ASSERTION(IsEmpty(),
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"Non-empty event queue being destroyed; events being leaked.");
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if (mHead) {
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FreePage(mHead);
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}
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}
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bool
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nsEventQueue::GetEvent(bool aMayWait, nsIRunnable** aResult,
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MutexAutoLock& aProofOfLock)
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{
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while (IsEmpty()) {
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if (!aMayWait) {
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if (aResult) {
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*aResult = nullptr;
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}
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return false;
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}
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LOG(("EVENTQ(%p): wait begin\n", this));
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mEventsAvailable.Wait();
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LOG(("EVENTQ(%p): wait end\n", this));
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}
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if (aResult) {
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MOZ_ASSERT(mOffsetHead < EVENTS_PER_PAGE);
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MOZ_ASSERT_IF(mHead == mTail, mOffsetHead <= mOffsetTail);
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*aResult = mHead->mEvents[mOffsetHead++];
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MOZ_ASSERT(*aResult);
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MOZ_ASSERT(mOffsetHead <= EVENTS_PER_PAGE);
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// Check if mHead points to empty Page
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if (mOffsetHead == EVENTS_PER_PAGE) {
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Page* dead = mHead;
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mHead = mHead->mNext;
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FreePage(dead);
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mOffsetHead = 0;
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}
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}
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return true;
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}
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void
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nsEventQueue::PutEvent(already_AddRefed<nsIRunnable>&& aRunnable,
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MutexAutoLock& aProofOfLock)
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{
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if (!mHead) {
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mHead = NewPage();
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MOZ_ASSERT(mHead);
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mTail = mHead;
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mOffsetHead = 0;
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mOffsetTail = 0;
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} else if (mOffsetTail == EVENTS_PER_PAGE) {
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Page* page = NewPage();
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MOZ_ASSERT(page);
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mTail->mNext = page;
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mTail = page;
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mOffsetTail = 0;
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}
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nsIRunnable*& queueLocation = mTail->mEvents[mOffsetTail];
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MOZ_ASSERT(!queueLocation);
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queueLocation = aRunnable.take();
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++mOffsetTail;
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LOG(("EVENTQ(%p): notify\n", this));
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mEventsAvailable.Notify();
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}
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void
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nsEventQueue::PutEvent(nsIRunnable* aRunnable, MutexAutoLock& aProofOfLock)
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{
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nsCOMPtr<nsIRunnable> event(aRunnable);
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PutEvent(event.forget(), aProofOfLock);
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}
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size_t
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nsEventQueue::Count(MutexAutoLock& aProofOfLock)
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{
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// It is obvious count is 0 when the queue is empty.
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if (!mHead) {
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return 0;
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}
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/* How we count the number of events in the queue:
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* 1. Let pageCount(x, y) denote the number of pages excluding the tail page
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* where x is the index of head page and y is the index of the tail page.
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* 2. Then we have pageCount(x, y) = y - x.
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*
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* Ex: pageCount(0, 0) = 0 where both head and tail pages point to page 0.
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* pageCount(0, 1) = 1 where head points to page 0 and tail points page 1.
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*
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* 3. number of events = (EVENTS_PER_PAGE * pageCount(x, y))
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* - (empty slots in head page) + (non-empty slots in tail page)
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* = (EVENTS_PER_PAGE * pageCount(x, y)) - mOffsetHead + mOffsetTail
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*/
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int count = -mOffsetHead;
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// Compute (EVENTS_PER_PAGE * pageCount(x, y))
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for (Page* page = mHead; page != mTail; page = page->mNext) {
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count += EVENTS_PER_PAGE;
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}
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count += mOffsetTail;
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MOZ_ASSERT(count >= 0);
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return count;
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}
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