1 /*

     2  * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.

     3  * Copyright (C) 2009 Google Inc. All rights reserved.

     4  *

     5  * Redistribution and use in source and binary forms, with or without

     6  * modification, are permitted provided that the following conditions

     7  * are met:

     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  *

    14  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY

    15  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

    16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

    17  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR

    18  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

    19  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

    20  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

    21  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY

    22  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

    23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

    24  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 

    25  */

    26 

    27 #include "config.h"

    28 #include "ThreadTimers.h"

    29 

    30 #include "SharedTimer.h"

    31 #include "ThreadGlobalData.h"

    32 #include "Timer.h"

    33 #include <wtf/CurrentTime.h>

    34 

    35 namespace WebCore {

    36 

    37 // Fire timers for this length of time, and then quit to let the run loop process user input events.

    38 // 100ms is about a perceptable delay in UI, so use a half of that as a threshold.

    39 // This is to prevent UI freeze when there are too many timers or machine performance is low.

    40 static const double maxDurationOfFiringTimers = 0.050;

    41 

    42 // Timers are created, started and fired on the same thread, and each thread has its own ThreadTimers

    43 // copy to keep the heap and a set of currently firing timers.

    44 

    45 static MainThreadSharedTimer* mainThreadSharedTimer()

    46 {

    47     static MainThreadSharedTimer* timer = new MainThreadSharedTimer;

    48     return timer;

    49 }

    50 

    51 ThreadTimers::ThreadTimers()

    52     : m_sharedTimer(0)

    53     , m_firingTimers(false)

    54 {

    55     if (isMainThread())

    56         setSharedTimer(mainThreadSharedTimer());

    57 }

    58 

    59 // A worker thread may initialize SharedTimer after some timers are created.

    60 // Also, SharedTimer can be replaced with 0 before all timers are destroyed.

    61 void ThreadTimers::setSharedTimer(SharedTimer* sharedTimer)

    62 {

    63     if (m_sharedTimer) {

    64         m_sharedTimer->setFiredFunction(0);

    65         m_sharedTimer->stop();

    66     }

    67     

    68     m_sharedTimer = sharedTimer;

    69     

    70     if (sharedTimer) {

    71         m_sharedTimer->setFiredFunction(ThreadTimers::sharedTimerFired);

    72         updateSharedTimer();

    73     }

    74 }

    75 

    76 void ThreadTimers::updateSharedTimer()

    77 {

    78     if (!m_sharedTimer)

    79         return;

    80         

    81     if (m_firingTimers || m_timerHeap.isEmpty())

    82         m_sharedTimer->stop();

    83     else

    84         m_sharedTimer->setFireTime(m_timerHeap.first()->m_nextFireTime);

    85 }

    86 

    87 void ThreadTimers::sharedTimerFired()

    88 {

    89     // Redirect to non-static method.

    90     threadGlobalData().threadTimers().sharedTimerFiredInternal();

    91 }

    92 

    93 void ThreadTimers::sharedTimerFiredInternal()

    94 {

    95     // Do a re-entrancy check.

    96     if (m_firingTimers)

    97         return;

    98     m_firingTimers = true;

    99 

   100     double fireTime = currentTime();

   101     double timeToQuit = fireTime + maxDurationOfFiringTimers;

   102 

   103     while (!m_timerHeap.isEmpty() && m_timerHeap.first()->m_nextFireTime <= fireTime) {

   104         TimerBase* timer = m_timerHeap.first();

   105         timer->m_nextFireTime = 0;

   106         timer->heapDeleteMin();

   107 

   108         double interval = timer->repeatInterval();

   109         timer->setNextFireTime(interval ? fireTime + interval : 0);

   110 

   111         // Once the timer has been fired, it may be deleted, so do nothing else with it after this point.

   112         timer->fired();

   113 

   114         // Catch the case where the timer asked timers to fire in a nested event loop, or we are over time limit.

   115         if (!m_firingTimers || timeToQuit < currentTime())

   116             break;

   117     }

   118 

   119     m_firingTimers = false;

   120 

   121     updateSharedTimer();

   122 }

   123 

   124 void ThreadTimers::fireTimersInNestedEventLoop()

   125 {

   126     // Reset the reentrancy guard so the timers can fire again.

   127     m_firingTimers = false;

   128     updateSharedTimer();

   129 }

   130 

   131 } // namespace WebCore

   132