From f587e8f4fd670f11fa1e878c1015d7241033559a Mon Sep 17 00:00:00 2001 From: Thiago Macieira Date: Sat, 11 Aug 2012 16:03:51 +0200 Subject: [PATCH] Avoid calling QElapsedTimer::nsecsElapsed before the first futex sleep 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 Reviewed-by: Olivier Goffart --- src/corelib/thread/qmutex_linux.cpp | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/src/corelib/thread/qmutex_linux.cpp b/src/corelib/thread/qmutex_linux.cpp index 0c44d18b8f..e2842a670b 100644 --- a/src/corelib/thread/qmutex_linux.cpp +++ b/src/corelib/thread/qmutex_linux.cpp @@ -184,15 +184,18 @@ bool lockInternal_helper(QBasicAtomicPointer &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 &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);