wtf/MainThread.cpp

   1 /*
   2  * Copyright (C) 2007, 2008 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  * 1.  Redistributions of source code must retain the above copyright
   9  *     notice, this list of conditions and the following disclaimer.
  10  * 2.  Redistributions in binary form must reproduce the above copyright
  11  *     notice, this list of conditions and the following disclaimer in the
  12  *     documentation and/or other materials provided with the distribution.
  13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
  14  *     its contributors may be used to endorse or promote products derived
  15  *     from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #include "config.h"
  30 #include "MainThread.h"
  31
  32 #include "StdLibExtras.h"
  33 #include "CurrentTime.h"
  34 #include "Deque.h"
  35 #include "Threading.h"
  36
  37 namespace WTF {
  38
  39 struct FunctionWithContext {
  40     MainThreadFunction* function;
  41     void* context;
  42     ThreadCondition* syncFlag;
  43
  44     FunctionWithContext(MainThreadFunction* function = 0, void* context = 0, ThreadCondition* syncFlag = 0)
  45         : function(function)
  46         , context(context)
  47         , syncFlag(syncFlag)
  48     {
  49     }
  50 };
  51
  52 typedef Deque<FunctionWithContext> FunctionQueue;
  53
  54 static bool callbacksPaused; // This global variable is only accessed from main thread.
  55
  56 Mutex& mainThreadFunctionQueueMutex()
  57 {
  58     DEFINE_STATIC_LOCAL(Mutex, staticMutex, ());
  59     return staticMutex;
  60 }
  61
  62 static FunctionQueue& functionQueue()
  63 {
  64     DEFINE_STATIC_LOCAL(FunctionQueue, staticFunctionQueue, ());
  65     return staticFunctionQueue;
  66 }
  67
  68 void initializeMainThread()
  69 {
  70     mainThreadFunctionQueueMutex();
  71     initializeMainThreadPlatform();
  72 }
  73
  74 // 0.1 sec delays in UI is approximate threshold when they become noticeable. Have a limit that's half of that.
  75 static const double maxRunLoopSuspensionTime = 0.05;
  76
  77 void dispatchFunctionsFromMainThread()
  78 {
  79     ASSERT(isMainThread());
  80
  81     if (callbacksPaused)
  82         return;
  83
  84     double startTime = currentTime();
  85
  86     FunctionWithContext invocation;
  87     while (true) {
  88         {
  89             MutexLocker locker(mainThreadFunctionQueueMutex());
  90             if (!functionQueue().size())
  91                 break;
  92             invocation = functionQueue().first();
  93             functionQueue().removeFirst();
  94         }
  95
  96         invocation.function(invocation.context);
  97         if (invocation.syncFlag)
  98             invocation.syncFlag->signal();
  99
 100         // If we are running accumulated functions for too long so UI may become unresponsive, we need to
 101         // yield so the user input can be processed. Otherwise user may not be able to even close the window.
 102         // This code has effect only in case the scheduleDispatchFunctionsOnMainThread() is implemented in a way that
 103         // allows input events to be processed before we are back here.
 104         if (currentTime() - startTime > maxRunLoopSuspensionTime) {
 105             scheduleDispatchFunctionsOnMainThread();
 106             break;
 107         }
 108     }
 109 }
 110
 111 void callOnMainThread(MainThreadFunction* function, void* context)
 112 {
 113     ASSERT(function);
 114     bool needToSchedule = false;
 115     {
 116         MutexLocker locker(mainThreadFunctionQueueMutex());
 117         needToSchedule = functionQueue().size() == 0;
 118         functionQueue().append(FunctionWithContext(function, context));
 119     }
 120     if (needToSchedule)
 121         scheduleDispatchFunctionsOnMainThread();
 122 }
 123
 124 void callOnMainThreadAndWait(MainThreadFunction* function, void* context)
 125 {
 126     ASSERT(function);
 127
 128     if (isMainThread()) {
 129         function(context);
 130         return;
 131     }
 132
 133     ThreadCondition syncFlag;
 134     Mutex& functionQueueMutex = mainThreadFunctionQueueMutex();
 135     MutexLocker locker(functionQueueMutex);
 136     functionQueue().append(FunctionWithContext(function, context, &syncFlag));
 137     if (functionQueue().size() == 1)
 138         scheduleDispatchFunctionsOnMainThread();
 139     syncFlag.wait(functionQueueMutex);
 140 }
 141
 142 void setMainThreadCallbacksPaused(bool paused)
 143 {
 144     ASSERT(isMainThread());
 145
 146     if (callbacksPaused == paused)
 147         return;
 148
 149     callbacksPaused = paused;
 150
 151     if (!callbacksPaused)
 152         scheduleDispatchFunctionsOnMainThread();
 153 }
 154
 155 } // namespace WTF