The Tor Browser: xpcom/threads/nsEventQueue.cpp@b8a032363ba2

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

     2 /* vim:set ts=2 sw=2 sts=2 et cindent: */

     3 /* This Source Code Form is subject to the terms of the Mozilla Public

     4  * License, v. 2.0. If a copy of the MPL was not distributed with this

     5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     7 #include "nsEventQueue.h"

     8 #include "nsAutoPtr.h"

     9 #include "prlog.h"

    10 #include "nsThreadUtils.h"

    11 #include "prthread.h"

    12 #include "mozilla/ChaosMode.h"

    14 using namespace mozilla;

    16 #ifdef PR_LOGGING

    17 static PRLogModuleInfo *

    18 GetLog()

    19 {

    20   static PRLogModuleInfo *sLog;

    21   if (!sLog)

    22     sLog = PR_NewLogModule("nsEventQueue");

    23   return sLog;

    24 }

    25 #endif

    26 #ifdef LOG

    27 #undef LOG

    28 #endif

    29 #define LOG(args) PR_LOG(GetLog(), PR_LOG_DEBUG, args)

    31 nsEventQueue::nsEventQueue()

    32   : mReentrantMonitor("nsEventQueue.mReentrantMonitor")

    33   , mHead(nullptr)

    34   , mTail(nullptr)

    35   , mOffsetHead(0)

    36   , mOffsetTail(0)

    37 {

    38 }

    40 nsEventQueue::~nsEventQueue()

    41 {

    42   // It'd be nice to be able to assert that no one else is holding the monitor,

    43   // but NSPR doesn't really expose APIs for it.

    44   NS_ASSERTION(IsEmpty(), "Non-empty event queue being destroyed; events being leaked.");

    46   if (mHead)

    47     FreePage(mHead);

    48 }

    50 bool

    51 nsEventQueue::GetEvent(bool mayWait, nsIRunnable **result)

    52 {

    53   {

    54     ReentrantMonitorAutoEnter mon(mReentrantMonitor);

    56     while (IsEmpty()) {

    57       if (!mayWait) {

    58         if (result)

    59           *result = nullptr;

    60         return false;

    61       }

    62       LOG(("EVENTQ(%p): wait begin\n", this));

    63       mon.Wait();

    64       LOG(("EVENTQ(%p): wait end\n", this));

    65     }

    67     if (result) {

    68       *result = mHead->mEvents[mOffsetHead++];

    70       // Check if mHead points to empty Page

    71       if (mOffsetHead == EVENTS_PER_PAGE) {

    72         Page *dead = mHead;

    73         mHead = mHead->mNext;

    74         FreePage(dead);

    75         mOffsetHead = 0;

    76       }

    77     }

    78   }

    80   return true;

    81 }

    83 bool

    84 nsEventQueue::PutEvent(nsIRunnable *runnable)

    85 {

    86   // Avoid calling AddRef+Release while holding our monitor.

    87   nsRefPtr<nsIRunnable> event(runnable);

    88   bool rv = true;

    89   {

    90     if (ChaosMode::isActive()) {

    91       // With probability 0.5, yield so other threads have a chance to

    92       // dispatch events to this queue first.

    93       if (ChaosMode::randomUint32LessThan(2)) {

    94         PR_Sleep(PR_INTERVAL_NO_WAIT);

    95       }

    96     }

    98     ReentrantMonitorAutoEnter mon(mReentrantMonitor);

   100     if (!mHead) {

   101       mHead = NewPage();

   102       if (!mHead) {

   103         rv = false;

   104       } else {

   105         mTail = mHead;

   106         mOffsetHead = 0;

   107         mOffsetTail = 0;

   108       }

   109     } else if (mOffsetTail == EVENTS_PER_PAGE) {

   110       Page *page = NewPage();

   111       if (!page) {

   112         rv = false;

   113       } else {

   114         mTail->mNext = page;

   115         mTail = page;

   116         mOffsetTail = 0;

   117       }

   118     }

   119     if (rv) {

   120       event.swap(mTail->mEvents[mOffsetTail]);

   121       ++mOffsetTail;

   122       LOG(("EVENTQ(%p): notify\n", this));

   123       mon.NotifyAll();

   124     }

   125   }

   126   return rv;

   127 }

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