gecko-dev/xpcom/threads/TimerThread.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is Netscape Communications
* Corporation. Portions created by the Initial Developer are
* Copyright (C) 2001 the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Stuart Parmenter <pavlov@netscape.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*/
#include "nsTimerImpl.h"
#include "TimerThread.h"
#include "nsAutoLock.h"
#include "pratom.h"
#include "nsIServiceManager.h"
NS_IMPL_THREADSAFE_ISUPPORTS1(TimerThread, nsIRunnable)
TimerThread::TimerThread() :
mLock(nsnull),
mCondVar(nsnull),
mShutdown(PR_FALSE),
mWaiting(PR_FALSE),
mDelayLineCounter(0),
mMinTimerPeriod(0),
mTimeoutAdjustment(0)
{
NS_INIT_REFCNT();
}
TimerThread::~TimerThread()
{
if (mCondVar)
PR_DestroyCondVar(mCondVar);
if (mLock)
PR_DestroyLock(mLock);
mThread = nsnull;
PRInt32 n = mTimers.Count();
while (--n >= 0) {
nsTimerImpl *timer = NS_STATIC_CAST(nsTimerImpl *, mTimers[n]);
NS_RELEASE(timer);
}
}
nsresult TimerThread::Init()
{
if (mThread)
return NS_OK;
mLock = PR_NewLock();
if (!mLock)
return NS_ERROR_OUT_OF_MEMORY;
mCondVar = PR_NewCondVar(mLock);
if (!mCondVar)
return NS_ERROR_OUT_OF_MEMORY;
nsresult rv;
mEventQueueService = do_GetService("@mozilla.org/event-queue-service;1", &rv);
if (NS_FAILED(rv))
return rv;
// We hold on to mThread to keep the thread alive.
rv = NS_NewThread(getter_AddRefs(mThread),
NS_STATIC_CAST(nsIRunnable*, this),
0,
PR_JOINABLE_THREAD,
PR_PRIORITY_NORMAL,
PR_GLOBAL_THREAD);
return rv;
}
nsresult TimerThread::Shutdown()
{
if (!mThread)
return NS_ERROR_NOT_INITIALIZED;
{ // lock scope
nsAutoLock lock(mLock);
mShutdown = PR_TRUE;
// notify the cond var so that Run() can return
if (mCondVar && mWaiting)
PR_NotifyCondVar(mCondVar);
nsTimerImpl *timer;
for (PRInt32 i = mTimers.Count() - 1; i >= 0; i--) {
timer = NS_STATIC_CAST(nsTimerImpl*, mTimers[i]);
RemoveTimerInternal(timer);
}
}
mThread->Join(); // wait for the thread to die
return NS_OK;
}
// Keep track of how early (positive slack) or late (negative slack) timers
// are running, and use the filtered slack number to adaptively estimate how
// early timers should fire to be "on time".
void TimerThread::UpdateFilter(PRUint32 aDelay, PRIntervalTime aTimeout,
PRIntervalTime aNow)
{
PRInt32 slack = (PRInt32) (aTimeout - aNow);
double smoothSlack = 0;
PRUint32 i, filterLength;
static PRIntervalTime kFilterFeedbackMaxTicks =
PR_MillisecondsToInterval(FILTER_FEEDBACK_MAX);
if (slack > 0) {
if (slack > (PRInt32)kFilterFeedbackMaxTicks)
slack = kFilterFeedbackMaxTicks;
} else {
if (slack < -(PRInt32)kFilterFeedbackMaxTicks)
slack = -(PRInt32)kFilterFeedbackMaxTicks;
}
mDelayLine[mDelayLineCounter & DELAY_LINE_LENGTH_MASK] = slack;
if (++mDelayLineCounter < DELAY_LINE_LENGTH) {
// Startup mode: accumulate a full delay line before filtering.
PR_ASSERT(mTimeoutAdjustment == 0);
filterLength = 0;
} else {
// Past startup: compute number of filter taps based on mMinTimerPeriod.
if (mMinTimerPeriod == 0) {
mMinTimerPeriod = (aDelay != 0) ? aDelay : 1;
} else if (aDelay != 0 && aDelay < mMinTimerPeriod) {
mMinTimerPeriod = aDelay;
}
filterLength = (PRUint32) (FILTER_DURATION / mMinTimerPeriod);
if (filterLength > DELAY_LINE_LENGTH)
filterLength = DELAY_LINE_LENGTH;
else if (filterLength < 4)
filterLength = 4;
for (i = 1; i <= filterLength; i++)
smoothSlack += mDelayLine[(mDelayLineCounter-i) & DELAY_LINE_LENGTH_MASK];
smoothSlack /= filterLength;
// XXXbe do we need amplification? hacking a fudge factor, need testing...
mTimeoutAdjustment = (PRInt32) (smoothSlack * 1.5);
}
#ifdef DEBUG_TIMERS
if (PR_LOG_TEST(gTimerLog, PR_LOG_DEBUG)) {
PR_LOG(gTimerLog, PR_LOG_DEBUG,
("UpdateFilter: smoothSlack = %g, filterLength = %u\n",
smoothSlack, filterLength));
}
#endif
}
/* void Run(); */
NS_IMETHODIMP TimerThread::Run()
{
nsAutoLock lock(mLock);
while (!mShutdown) {
PRIntervalTime now = PR_IntervalNow();
nsTimerImpl *timer = nsnull;
if (mTimers.Count() > 0) {
timer = NS_STATIC_CAST(nsTimerImpl*, mTimers[0]);
if (!TIMER_LESS_THAN(now, timer->mTimeout + mTimeoutAdjustment)) {
next:
// NB: AddRef before the Release under RemoveTimerInternal to avoid
// mRefCnt passing through zero, in case all other refs than the one
// from mTimers have gone away (the last non-mTimers[i]-ref's Release
// must be racing with us, blocked in gThread->RemoveTimer waiting
// for TimerThread::mLock, under nsTimerImpl::Release.
NS_ADDREF(timer);
RemoveTimerInternal(timer);
// We release mLock around the Fire call, of course, to avoid deadlock.
lock.unlock();
#ifdef DEBUG_TIMERS
if (PR_LOG_TEST(gTimerLog, PR_LOG_DEBUG)) {
PR_LOG(gTimerLog, PR_LOG_DEBUG,
("Timer thread woke up %dms from when it was supposed to\n",
(now >= timer->mTimeout)
? PR_IntervalToMilliseconds(now - timer->mTimeout)
: -(PRInt32)PR_IntervalToMilliseconds(timer->mTimeout - now))
);
}
#endif
// We are going to let the call to PostTimerEvent here handle the release of the
// timer so that we don't end up releasing the timer on the TimerThread
// instead of on the thread it targets.
timer->PostTimerEvent();
timer = nsnull;
lock.lock();
if (mShutdown)
break;
// Update now, as PostTimerEvent plus the locking may have taken a tick or two,
// and we may goto next below.
now = PR_IntervalNow();
}
}
PRIntervalTime waitFor = PR_INTERVAL_NO_TIMEOUT;
if (mTimers.Count() > 0) {
timer = NS_STATIC_CAST(nsTimerImpl *, mTimers[0]);
PRIntervalTime timeout = timer->mTimeout + mTimeoutAdjustment;
// Don't wait at all (even for PR_INTERVAL_NO_WAIT) if the next timer is
// due now or overdue.
if (!TIMER_LESS_THAN(now, timeout))
goto next;
waitFor = timeout - now;
}
#ifdef DEBUG_TIMERS
if (PR_LOG_TEST(gTimerLog, PR_LOG_DEBUG)) {
if (waitFor == PR_INTERVAL_NO_TIMEOUT)
PR_LOG(gTimerLog, PR_LOG_DEBUG,
("waiting for PR_INTERVAL_NO_TIMEOUT\n"));
else
PR_LOG(gTimerLog, PR_LOG_DEBUG,
("waiting for %u\n", PR_IntervalToMilliseconds(waitFor)));
}
#endif
mWaiting = PR_TRUE;
PR_WaitCondVar(mCondVar, waitFor);
mWaiting = PR_FALSE;
}
return NS_OK;
}
nsresult TimerThread::AddTimer(nsTimerImpl *aTimer)
{
nsAutoLock lock(mLock);
// Add the timer to our list.
PRInt32 i = AddTimerInternal(aTimer);
if (i < 0)
return NS_ERROR_OUT_OF_MEMORY;
// Awaken the timer thread.
if (mCondVar && mWaiting && i == 0)
PR_NotifyCondVar(mCondVar);
return NS_OK;
}
nsresult TimerThread::TimerDelayChanged(nsTimerImpl *aTimer)
{
nsAutoLock lock(mLock);
// Our caller has a strong ref to aTimer, so it can't go away here under
// ReleaseTimerInternal.
RemoveTimerInternal(aTimer);
PRInt32 i = AddTimerInternal(aTimer);
if (i < 0)
return NS_ERROR_OUT_OF_MEMORY;
// Awaken the timer thread.
if (mCondVar && mWaiting && i == 0)
PR_NotifyCondVar(mCondVar);
return NS_OK;
}
nsresult TimerThread::RemoveTimer(nsTimerImpl *aTimer)
{
nsAutoLock lock(mLock);
// Remove the timer from our array. Tell callers that aTimer was not found
// by returning NS_ERROR_NOT_AVAILABLE. Unlike the TimerDelayChanged case
// immediately above, our caller may be passing a (now-)weak ref in via the
// aTimer param, specifically when nsTimerImpl::Release loses a race with
// TimerThread::Run, must wait for the mLock auto-lock here, and during the
// wait Run drops the only remaining ref to aTimer via RemoveTimerInternal.
if (!RemoveTimerInternal(aTimer))
return NS_ERROR_NOT_AVAILABLE;
// Awaken the timer thread.
if (mCondVar && mWaiting)
PR_NotifyCondVar(mCondVar);
return NS_OK;
}
// This function must be called from within a lock
PRInt32 TimerThread::AddTimerInternal(nsTimerImpl *aTimer)
{
PRInt32 count = mTimers.Count();
PRInt32 i = 0;
for (; i < count; i++) {
nsTimerImpl *timer = NS_STATIC_CAST(nsTimerImpl *, mTimers[i]);
if (TIMER_LESS_THAN(aTimer->mTimeout, timer->mTimeout)) {
break;
}
}
if (!mTimers.InsertElementAt(aTimer, i))
return -1;
aTimer->mArmed = PR_TRUE;
NS_ADDREF(aTimer);
return i;
}
PRBool TimerThread::RemoveTimerInternal(nsTimerImpl *aTimer)
{
if (!mTimers.RemoveElement(aTimer))
return PR_FALSE;
// Order is crucial here -- see nsTimerImpl::Release.
aTimer->mArmed = PR_FALSE;
NS_RELEASE(aTimer);
return PR_TRUE;
}