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Avoid calling QElapsedTimer::nsecsElapsed before the first futex sleep

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The first time we're going to sleep, the timeout should be exactly the
value that was passed by the user. We don't need to calculate the time
elapsed between start() and a few lines below.

Change-Id: I99c363b6f0ecfd07ad787b79b75e61771733c2b3
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
This commit is contained in:
Thiago Macieira 2012-08-11 16:03:51 +02:00 committed by Qt by Nokia
parent d8eb52fc45
commit f587e8f4fd
1 changed files with 8 additions and 4 deletions
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12
src/corelib/thread/qmutex_linux.cpp
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@ -184,15 +184,18 @@ bool lockInternal_helper(QBasicAtomicPointer<QMutexData> &d_ptr, int timeout = -
if (timeout == 0)
return false;
struct timespec ts, *pts = 0;
QElapsedTimer elapsedTimer;
checkElapsedTimerIsTrivial();
if (IsTimed)
if (IsTimed) {
ts.tv_sec = timeout / Q_INT64_C(1000) / 1000 / 1000;
ts.tv_nsec = timeout % Q_INT64_C(1000) * 1000 * 1000;
elapsedTimer.start();
}
// the mutex is locked already, set a bit indicating we're waiting
while (d_ptr.fetchAndStoreAcquire(dummyFutexValue()) != 0) {
struct timespec ts, *pts = 0;
if (IsTimed) {
if (IsTimed && pts == &ts) {
// recalculate the timeout
qint64 xtimeout = qint64(timeout) * 1000 * 1000;
xtimeout -= elapsedTimer.nsecsElapsed();
@ -202,8 +205,9 @@ bool lockInternal_helper(QBasicAtomicPointer<QMutexData> &d_ptr, int timeout = -
}
ts.tv_sec = xtimeout / Q_INT64_C(1000) / 1000 / 1000;
ts.tv_nsec = xtimeout % (Q_INT64_C(1000) * 1000 * 1000);
pts = &ts;
}
if (IsTimed)
pts = &ts;
// successfully set the waiting bit, now sleep
int r = _q_futex(&d_ptr, FUTEX_WAIT, quintptr(dummyFutexValue()), pts);