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 "CurrentTime.h"

    33 #include "Deque.h"

    34 #include "StdLibExtras.h"

    35 #include "Threading.h"

    36 

    37 #if PLATFORM(CHROMIUM)

    38 #error Chromium uses a different main thread implementation

    39 #endif

    40 

    41 namespace WTF {

    42 

    43 struct FunctionWithContext {

    44     MainThreadFunction* function;

    45     void* context;

    46     ThreadCondition* syncFlag;

    47 

    48     FunctionWithContext(MainThreadFunction* function = 0, void* context = 0, ThreadCondition* syncFlag = 0)

    49         : function(function)

    50         , context(context)

    51         , syncFlag(syncFlag)

    52     { 

    53     }

    54     bool operator == (const FunctionWithContext& o)

    55     {

    56         return function == o.function

    57             && context == o.context

    58             && syncFlag == o.syncFlag;

    59     }

    60 };

    61 

    62 class FunctionWithContextFinder {

    63 public:

    64     FunctionWithContextFinder(const FunctionWithContext& m) : m(m) {}

    65     bool operator() (FunctionWithContext& o) { return o == m; }

    66     FunctionWithContext m;

    67 };

    68 

    69 

    70 typedef Deque<FunctionWithContext> FunctionQueue;

    71 

    72 static bool callbacksPaused; // This global variable is only accessed from main thread.

    73 #if !PLATFORM(MAC) && !PLATFORM(QT)

    74 static ThreadIdentifier mainThreadIdentifier;

    75 #endif

    76 

    77 static Mutex& mainThreadFunctionQueueMutex()

    78 {

    79     DEFINE_STATIC_LOCAL(Mutex, staticMutex, ());

    80     return staticMutex;

    81 }

    82 

    83 static FunctionQueue& functionQueue()

    84 {

    85     DEFINE_STATIC_LOCAL(FunctionQueue, staticFunctionQueue, ());

    86     return staticFunctionQueue;

    87 }

    88 

    89 

    90 #if !PLATFORM(MAC)

    91 

    92 void initializeMainThread()

    93 {

    94     static bool initializedMainThread;

    95     if (initializedMainThread)

    96         return;

    97     initializedMainThread = true;

    98 

    99 #if !PLATFORM(QT)

   100     mainThreadIdentifier = currentThread();

   101 #endif

   102 

   103     mainThreadFunctionQueueMutex();

   104     initializeMainThreadPlatform();

   105 }

   106 

   107 #else

   108 

   109 static pthread_once_t initializeMainThreadKeyOnce = PTHREAD_ONCE_INIT;

   110 

   111 static void initializeMainThreadOnce()

   112 {

   113     mainThreadFunctionQueueMutex();

   114     initializeMainThreadPlatform();

   115 }

   116 

   117 void initializeMainThread()

   118 {

   119     pthread_once(&initializeMainThreadKeyOnce, initializeMainThreadOnce);

   120 }

   121 

   122 static void initializeMainThreadToProcessMainThreadOnce()

   123 {

   124     mainThreadFunctionQueueMutex();

   125     initializeMainThreadToProcessMainThreadPlatform();

   126 }

   127 

   128 void initializeMainThreadToProcessMainThread()

   129 {

   130     pthread_once(&initializeMainThreadKeyOnce, initializeMainThreadToProcessMainThreadOnce);

   131 }

   132 #endif

   133 

   134 // 0.1 sec delays in UI is approximate threshold when they become noticeable. Have a limit that's half of that.

   135 static const double maxRunLoopSuspensionTime = 0.05;

   136 

   137 void dispatchFunctionsFromMainThread()

   138 {

   139     ASSERT(isMainThread());

   140 

   141     if (callbacksPaused)

   142         return;

   143 

   144     double startTime = currentTime();

   145 

   146     FunctionWithContext invocation;

   147     while (true) {

   148         {

   149             MutexLocker locker(mainThreadFunctionQueueMutex());

   150             if (!functionQueue().size())

   151                 break;

   152             invocation = functionQueue().takeFirst();

   153         }

   154 

   155         invocation.function(invocation.context);

   156         if (invocation.syncFlag)

   157             invocation.syncFlag->signal();

   158 

   159         // If we are running accumulated functions for too long so UI may become unresponsive, we need to

   160         // yield so the user input can be processed. Otherwise user may not be able to even close the window.

   161         // This code has effect only in case the scheduleDispatchFunctionsOnMainThread() is implemented in a way that

   162         // allows input events to be processed before we are back here.

   163         if (currentTime() - startTime > maxRunLoopSuspensionTime) {

   164             scheduleDispatchFunctionsOnMainThread();

   165             break;

   166         }

   167     }

   168 }

   169 

   170 void callOnMainThread(MainThreadFunction* function, void* context)

   171 {

   172     ASSERT(function);

   173     bool needToSchedule = false;

   174     {

   175         MutexLocker locker(mainThreadFunctionQueueMutex());

   176         needToSchedule = functionQueue().size() == 0;

   177         functionQueue().append(FunctionWithContext(function, context));

   178     }

   179     if (needToSchedule)

   180         scheduleDispatchFunctionsOnMainThread();

   181 }

   182 

   183 void callOnMainThreadAndWait(MainThreadFunction* function, void* context)

   184 {

   185     ASSERT(function);

   186 

   187     if (isMainThread()) {

   188         function(context);

   189         return;

   190     }

   191 

   192     ThreadCondition syncFlag;

   193     Mutex& functionQueueMutex = mainThreadFunctionQueueMutex();

   194     MutexLocker locker(functionQueueMutex);

   195     functionQueue().append(FunctionWithContext(function, context, &syncFlag));

   196     if (functionQueue().size() == 1)

   197         scheduleDispatchFunctionsOnMainThread();

   198     syncFlag.wait(functionQueueMutex);

   199 }

   200 

   201 void cancelCallOnMainThread(MainThreadFunction* function, void* context)

   202 {

   203     ASSERT(function);

   204 

   205     MutexLocker locker(mainThreadFunctionQueueMutex());

   206 

   207     FunctionWithContextFinder pred(FunctionWithContext(function, context));

   208 

   209     while (true) {

   210         // We must redefine 'i' each pass, because the itererator's operator= 

   211         // requires 'this' to be valid, and remove() invalidates all iterators

   212         FunctionQueue::iterator i(functionQueue().findIf(pred));

   213         if (i == functionQueue().end())

   214             break;

   215         functionQueue().remove(i);

   216     }

   217 }

   218 

   219 void setMainThreadCallbacksPaused(bool paused)

   220 {

   221     ASSERT(isMainThread());

   222 

   223     if (callbacksPaused == paused)

   224         return;

   225 

   226     callbacksPaused = paused;

   227 

   228     if (!callbacksPaused)

   229         scheduleDispatchFunctionsOnMainThread();

   230 }

   231 

   232 #if !PLATFORM(MAC) && !PLATFORM(QT) && !PLATFORM(BREWMP)

   233 bool isMainThread()

   234 {

   235     return currentThread() == mainThreadIdentifier;

   236 }

   237 #endif

   238 

   239 } // namespace WTF