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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 "platform/ThreadTimers.h"
     29 
     30 #include "platform/SharedTimer.h"
     31 #include "platform/PlatformThreadData.h"
     32 #include "platform/Timer.h"
     33 #include "platform/TraceEvent.h"
     34 #include "wtf/CurrentTime.h"
     35 #include "wtf/MainThread.h"
     36 
     37 using namespace std;
     38 
     39 namespace WebCore {
     40 
     41 // Fire timers for this length of time, and then quit to let the run loop process user input events.
     42 // 100ms is about a perceptable delay in UI, so use a half of that as a threshold.
     43 // This is to prevent UI freeze when there are too many timers or machine performance is low.
     44 static const double maxDurationOfFiringTimers = 0.050;
     45 
     46 // Timers are created, started and fired on the same thread, and each thread has its own ThreadTimers
     47 // copy to keep the heap and a set of currently firing timers.
     48 
     49 static MainThreadSharedTimer* mainThreadSharedTimer()
     50 {
     51     static MainThreadSharedTimer* timer = new MainThreadSharedTimer;
     52     return timer;
     53 }
     54 
     55 ThreadTimers::ThreadTimers()
     56     : m_sharedTimer(0)
     57     , m_firingTimers(false)
     58     , m_pendingSharedTimerFireTime(0)
     59 {
     60     if (isMainThread())
     61         setSharedTimer(mainThreadSharedTimer());
     62 }
     63 
     64 // A worker thread may initialize SharedTimer after some timers are created.
     65 // Also, SharedTimer can be replaced with 0 before all timers are destroyed.
     66 void ThreadTimers::setSharedTimer(SharedTimer* sharedTimer)
     67 {
     68     if (m_sharedTimer) {
     69         m_sharedTimer->setFiredFunction(0);
     70         m_sharedTimer->stop();
     71         m_pendingSharedTimerFireTime = 0;
     72     }
     73 
     74     m_sharedTimer = sharedTimer;
     75 
     76     if (sharedTimer) {
     77         m_sharedTimer->setFiredFunction(ThreadTimers::sharedTimerFired);
     78         updateSharedTimer();
     79     }
     80 }
     81 
     82 void ThreadTimers::updateSharedTimer()
     83 {
     84     if (!m_sharedTimer)
     85         return;
     86 
     87     if (m_firingTimers || m_timerHeap.isEmpty()) {
     88         m_pendingSharedTimerFireTime = 0;
     89         m_sharedTimer->stop();
     90     } else {
     91         double nextFireTime = m_timerHeap.first()->m_nextFireTime;
     92         double currentMonotonicTime = monotonicallyIncreasingTime();
     93         if (m_pendingSharedTimerFireTime) {
     94             // No need to restart the timer if both the pending fire time and the new fire time are in the past.
     95             if (m_pendingSharedTimerFireTime <= currentMonotonicTime && nextFireTime <= currentMonotonicTime)
     96                 return;
     97         }
     98         m_pendingSharedTimerFireTime = nextFireTime;
     99         m_sharedTimer->setFireInterval(max(nextFireTime - currentMonotonicTime, 0.0));
    100     }
    101 }
    102 
    103 void ThreadTimers::sharedTimerFired()
    104 {
    105     TRACE_EVENT_SET_SAMPLING_STATE("Blink", "Internal");
    106 
    107     // Redirect to non-static method.
    108     PlatformThreadData::current().threadTimers().sharedTimerFiredInternal();
    109 
    110     TRACE_EVENT_SET_SAMPLING_STATE("Blink", "Sleeping");
    111 }
    112 
    113 void ThreadTimers::sharedTimerFiredInternal()
    114 {
    115     // Do a re-entrancy check.
    116     if (m_firingTimers)
    117         return;
    118     m_firingTimers = true;
    119     m_pendingSharedTimerFireTime = 0;
    120 
    121     double fireTime = monotonicallyIncreasingTime();
    122     double timeToQuit = fireTime + maxDurationOfFiringTimers;
    123 
    124     while (!m_timerHeap.isEmpty() && m_timerHeap.first()->m_nextFireTime <= fireTime) {
    125         TimerBase* timer = m_timerHeap.first();
    126         timer->m_nextFireTime = 0;
    127         timer->m_unalignedNextFireTime = 0;
    128         timer->heapDeleteMin();
    129 
    130         double interval = timer->repeatInterval();
    131         timer->setNextFireTime(interval ? fireTime + interval : 0);
    132 
    133         // Once the timer has been fired, it may be deleted, so do nothing else with it after this point.
    134         timer->fired();
    135 
    136         // Catch the case where the timer asked timers to fire in a nested event loop, or we are over time limit.
    137         if (!m_firingTimers || timeToQuit < monotonicallyIncreasingTime())
    138             break;
    139     }
    140 
    141     m_firingTimers = false;
    142 
    143     updateSharedTimer();
    144 }
    145 
    146 void ThreadTimers::fireTimersInNestedEventLoop()
    147 {
    148     // Reset the reentrancy guard so the timers can fire again.
    149     m_firingTimers = false;
    150     updateSharedTimer();
    151 }
    152 
    153 } // namespace WebCore
    154 
    155