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      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 
    133