diff --git a/src/corelib/io/qiodevice.cpp b/src/corelib/io/qiodevice.cpp
index f1c42c9bb5..35911934df 100644
--- a/src/corelib/io/qiodevice.cpp
+++ b/src/corelib/io/qiodevice.cpp
@@ -1667,6 +1667,23 @@ QString QIODevice::errorString() const
     \sa read(), write()
 */
 
+/*!
+  \internal
+  \fn int qt_subtract_from_timeout(int timeout, int elapsed)
+
+  Reduces the \a timeout by \a elapsed, taking into account that -1 is a
+  special value for timeouts.
+*/
+
+int qt_subtract_from_timeout(int timeout, int elapsed)
+{
+    if (timeout == -1)
+        return -1;
+
+    timeout = timeout - elapsed;
+    return timeout < 0 ? 0 : timeout;
+}
+
 
 #if !defined(QT_NO_DEBUG_STREAM)
 QDebug operator<<(QDebug debug, QIODevice::OpenMode modes)
diff --git a/src/corelib/io/qiodevice_p.h b/src/corelib/io/qiodevice_p.h
index d764cb0fbb..ddd222e9a8 100644
--- a/src/corelib/io/qiodevice_p.h
+++ b/src/corelib/io/qiodevice_p.h
@@ -60,6 +60,8 @@ QT_BEGIN_NAMESPACE
 #define QIODEVICE_BUFFERSIZE Q_INT64_C(16384)
 #endif
 
+Q_CORE_EXPORT int qt_subtract_from_timeout(int timeout, int elapsed);
+
 // This is QIODevice's read buffer, optimized for read(), isEmpty() and getChar()
 class QIODevicePrivateLinearBuffer
 {
diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp
index 94912ad616..baba9a0f9e 100644
--- a/src/corelib/io/qprocess.cpp
+++ b/src/corelib/io/qprocess.cpp
@@ -1793,8 +1793,7 @@ bool QProcess::waitForBytesWritten(int msecs)
         bool started = waitForStarted(msecs);
         if (!started)
             return false;
-        if (msecs != -1)
-            msecs -= stopWatch.elapsed();
+        msecs = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
     }
 
     return d->waitForBytesWritten(msecs);
@@ -1830,8 +1829,7 @@ bool QProcess::waitForFinished(int msecs)
         bool started = waitForStarted(msecs);
         if (!started)
             return false;
-        if (msecs != -1)
-            msecs -= stopWatch.elapsed();
+        msecs = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
     }
 
     return d->waitForFinished(msecs);
diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index cc154cfbc5..1c1c058c7a 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -1019,19 +1019,6 @@ void QProcessPrivate::killProcess()
         ::kill(pid_t(pid), SIGKILL);
 }
 
-/*
-   Returns the difference between msecs and elapsed. If msecs is -1,
-   however, -1 is returned.
-*/
-static int qt_timeout_value(int msecs, int elapsed)
-{
-    if (msecs == -1)
-        return -1;
-
-    int timeout = msecs - elapsed;
-    return timeout < 0 ? 0 : timeout;
-}
-
 bool QProcessPrivate::waitForStarted(int msecs)
 {
     Q_Q(QProcess);
@@ -1106,7 +1093,7 @@ bool QProcessPrivate::waitForReadyRead(int msecs)
         if (!stdinChannel.buffer.isEmpty() && stdinChannel.pipe[1] != -1)
             add_fd(nfds, stdinChannel.pipe[1], &fdwrite);
 
-        int timeout = qt_timeout_value(msecs, stopWatch.elapsed());
+        int timeout = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
 #ifdef Q_OS_BLACKBERRY
         int ret = bb_select(notifiers, nfds + 1, &fdread, &fdwrite, timeout);
 #else
@@ -1187,7 +1174,7 @@ bool QProcessPrivate::waitForBytesWritten(int msecs)
         if (!stdinChannel.buffer.isEmpty() && stdinChannel.pipe[1] != -1)
             add_fd(nfds, stdinChannel.pipe[1], &fdwrite);
 
-        int timeout = qt_timeout_value(msecs, stopWatch.elapsed());
+        int timeout = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
 #ifdef Q_OS_BLACKBERRY
         int ret = bb_select(notifiers, nfds + 1, &fdread, &fdwrite, timeout);
 #else
@@ -1262,7 +1249,7 @@ bool QProcessPrivate::waitForFinished(int msecs)
         if (!stdinChannel.buffer.isEmpty() && stdinChannel.pipe[1] != -1)
             add_fd(nfds, stdinChannel.pipe[1], &fdwrite);
 
-        int timeout = qt_timeout_value(msecs, stopWatch.elapsed());
+        int timeout = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
 #ifdef Q_OS_BLACKBERRY
         int ret = bb_select(notifiers, nfds + 1, &fdread, &fdwrite, timeout);
 #else
diff --git a/src/corelib/io/qwinoverlappedionotifier.cpp b/src/corelib/io/qwinoverlappedionotifier.cpp
index de0e205d26..7a005430ea 100644
--- a/src/corelib/io/qwinoverlappedionotifier.cpp
+++ b/src/corelib/io/qwinoverlappedionotifier.cpp
@@ -41,6 +41,7 @@
 #include <qthread.h>
 #include <qt_windows.h>
 #include <private/qobject_p.h>
+#include <private/qiodevice_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -332,11 +333,9 @@ bool QWinOverlappedIoNotifier::waitForNotified(int msecs, OVERLAPPED *overlapped
             return false;
         if (triggeredOverlapped == overlapped)
             return true;
-        if (msecs != -1) {
-            t = msecs - stopWatch.elapsed();
-            if (t < 0)
-                return false;
-        }
+        msecs = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
+        if (t == 0)
+            return false;
     }
 }
 
diff --git a/src/network/socket/qabstractsocket.cpp b/src/network/socket/qabstractsocket.cpp
index 5a1ad40b90..26667715be 100644
--- a/src/network/socket/qabstractsocket.cpp
+++ b/src/network/socket/qabstractsocket.cpp
@@ -1976,20 +1976,6 @@ QVariant QAbstractSocket::socketOption(QAbstractSocket::SocketOption option)
         return QVariant(ret);
 }
 
-
-/*
-   Returns the difference between msecs and elapsed. If msecs is -1,
-   however, -1 is returned.
-*/
-static int qt_timeout_value(int msecs, int elapsed)
-{
-    if (msecs == -1)
-        return -1;
-
-    int timeout = msecs - elapsed;
-    return timeout < 0 ? 0 : timeout;
-}
-
 /*!
     Waits until the socket is connected, up to \a msecs
     milliseconds. If the connection has been established, this
@@ -2067,7 +2053,7 @@ bool QAbstractSocket::waitForConnected(int msecs)
     int attempt = 1;
 #endif
     while (state() == ConnectingState && (msecs == -1 || stopWatch.elapsed() < msecs)) {
-        int timeout = qt_timeout_value(msecs, stopWatch.elapsed());
+        int timeout = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
         if (msecs != -1 && timeout > QT_CONNECT_TIMEOUT)
             timeout = QT_CONNECT_TIMEOUT;
 #if defined (QABSTRACTSOCKET_DEBUG)
@@ -2146,7 +2132,7 @@ bool QAbstractSocket::waitForReadyRead(int msecs)
         bool readyToRead = false;
         bool readyToWrite = false;
         if (!d->socketEngine->waitForReadOrWrite(&readyToRead, &readyToWrite, true, !d->writeBuffer.isEmpty(),
-                                               qt_timeout_value(msecs, stopWatch.elapsed()))) {
+                                               qt_subtract_from_timeout(msecs, stopWatch.elapsed()))) {
             d->socketError = d->socketEngine->error();
             setErrorString(d->socketEngine->errorString());
 #if defined (QABSTRACTSOCKET_DEBUG)
@@ -2169,7 +2155,7 @@ bool QAbstractSocket::waitForReadyRead(int msecs)
 
         if (state() != ConnectedState)
             return false;
-    } while (msecs == -1 || qt_timeout_value(msecs, stopWatch.elapsed()) > 0);
+    } while (msecs == -1 || qt_subtract_from_timeout(msecs, stopWatch.elapsed()) > 0);
     return false;
 }
 
@@ -2218,7 +2204,7 @@ bool QAbstractSocket::waitForBytesWritten(int msecs)
         bool readyToRead = false;
         bool readyToWrite = false;
         if (!d->socketEngine->waitForReadOrWrite(&readyToRead, &readyToWrite, true, !d->writeBuffer.isEmpty(),
-                                               qt_timeout_value(msecs, stopWatch.elapsed()))) {
+                                               qt_subtract_from_timeout(msecs, stopWatch.elapsed()))) {
             d->socketError = d->socketEngine->error();
             setErrorString(d->socketEngine->errorString());
 #if defined (QABSTRACTSOCKET_DEBUG)
@@ -2300,7 +2286,7 @@ bool QAbstractSocket::waitForDisconnected(int msecs)
         bool readyToWrite = false;
         if (!d->socketEngine->waitForReadOrWrite(&readyToRead, &readyToWrite, state() == ConnectedState,
                                                !d->writeBuffer.isEmpty(),
-                                               qt_timeout_value(msecs, stopWatch.elapsed()))) {
+                                               qt_subtract_from_timeout(msecs, stopWatch.elapsed()))) {
             d->socketError = d->socketEngine->error();
             setErrorString(d->socketEngine->errorString());
 #if defined (QABSTRACTSOCKET_DEBUG)
diff --git a/src/network/socket/qhttpsocketengine.cpp b/src/network/socket/qhttpsocketengine.cpp
index b929ee088e..7b601db79d 100644
--- a/src/network/socket/qhttpsocketengine.cpp
+++ b/src/network/socket/qhttpsocketengine.cpp
@@ -36,6 +36,7 @@
 #include "qhostaddress.h"
 #include "qurl.h"
 #include "private/qhttpnetworkreply_p.h"
+#include "private/qiodevice_p.h"
 #include "qelapsedtimer.h"
 #include "qnetworkinterface.h"
 
@@ -330,19 +331,6 @@ bool QHttpSocketEngine::setOption(SocketOption option, int value)
     return false;
 }
 
-/*
-   Returns the difference between msecs and elapsed. If msecs is -1,
-   however, -1 is returned.
-*/
-static int qt_timeout_value(int msecs, int elapsed)
-{
-    if (msecs == -1)
-        return -1;
-
-    int timeout = msecs - elapsed;
-    return timeout < 0 ? 0 : timeout;
-}
-
 bool QHttpSocketEngine::waitForRead(int msecs, bool *timedOut)
 {
     Q_D(const QHttpSocketEngine);
@@ -355,7 +343,7 @@ bool QHttpSocketEngine::waitForRead(int msecs, bool *timedOut)
 
     // Wait for more data if nothing is available.
     if (!d->socket->bytesAvailable()) {
-        if (!d->socket->waitForReadyRead(qt_timeout_value(msecs, stopWatch.elapsed()))) {
+        if (!d->socket->waitForReadyRead(qt_subtract_from_timeout(msecs, stopWatch.elapsed()))) {
             if (d->socket->state() == QAbstractSocket::UnconnectedState)
                 return true;
             setError(d->socket->error(), d->socket->errorString());
@@ -367,7 +355,7 @@ bool QHttpSocketEngine::waitForRead(int msecs, bool *timedOut)
 
     // If we're not connected yet, wait until we are, or until an error
     // occurs.
-    while (d->state != Connected && d->socket->waitForReadyRead(qt_timeout_value(msecs, stopWatch.elapsed()))) {
+    while (d->state != Connected && d->socket->waitForReadyRead(qt_subtract_from_timeout(msecs, stopWatch.elapsed()))) {
         // Loop while the protocol handshake is taking place.
     }
 
@@ -403,7 +391,7 @@ bool QHttpSocketEngine::waitForWrite(int msecs, bool *timedOut)
     // If we're not connected yet, wait until we are, and until bytes have
     // been received (i.e., the socket has connected, we have sent the
     // greeting, and then received the response).
-    while (d->state != Connected && d->socket->waitForReadyRead(qt_timeout_value(msecs, stopWatch.elapsed()))) {
+    while (d->state != Connected && d->socket->waitForReadyRead(qt_subtract_from_timeout(msecs, stopWatch.elapsed()))) {
         // Loop while the protocol handshake is taking place.
     }
 
diff --git a/src/network/socket/qsocks5socketengine.cpp b/src/network/socket/qsocks5socketengine.cpp
index 1634352333..60f1c2fa50 100644
--- a/src/network/socket/qsocks5socketengine.cpp
+++ b/src/network/socket/qsocks5socketengine.cpp
@@ -47,6 +47,7 @@
 #include "qcoreapplication.h"
 #include "qurl.h"
 #include "qauthenticator.h"
+#include "private/qiodevice_p.h"
 #include <qendian.h>
 #include <qnetworkinterface.h>
 
@@ -269,19 +270,6 @@ static int qt_socks5_get_host_address_and_port(const QByteArray &buf, QHostAddre
     return ret;
 }
 
-/*
-   Returns the difference between msecs and elapsed. If msecs is -1,
-   however, -1 is returned.
-*/
-static int qt_timeout_value(int msecs, int elapsed)
-{
-    if (msecs == -1)
-        return -1;
-
-    int timeout = msecs - elapsed;
-    return timeout < 0 ? 0 : timeout;
-}
-
 struct QSocks5Data
 {
     QTcpSocket *controlSocket;
@@ -1396,7 +1384,7 @@ bool QSocks5SocketEngine::bind(const QHostAddress &addr, quint16 port)
         dummy.setProxy(QNetworkProxy::NoProxy);
         if (!dummy.bind()
             || writeDatagram(0,0, d->data->controlSocket->localAddress(), dummy.localPort()) != 0
-            || !dummy.waitForReadyRead(qt_timeout_value(msecs, stopWatch.elapsed()))
+            || !dummy.waitForReadyRead(qt_subtract_from_timeout(msecs, stopWatch.elapsed()))
             || dummy.readDatagram(0,0, &d->localAddress, &d->localPort) != 0) {
             QSOCKS5_DEBUG << "udp actual address and port lookup failed";
             setState(QAbstractSocket::UnconnectedState);
@@ -1484,7 +1472,7 @@ void QSocks5SocketEngine::close()
             QElapsedTimer stopWatch;
             stopWatch.start();
             while (!d->data->controlSocket->bytesToWrite()) {
-               if (!d->data->controlSocket->waitForBytesWritten(qt_timeout_value(msecs, stopWatch.elapsed())))
+               if (!d->data->controlSocket->waitForBytesWritten(qt_subtract_from_timeout(msecs, stopWatch.elapsed())))
                    break;
             }
         }
@@ -1740,7 +1728,7 @@ bool QSocks5SocketEnginePrivate::waitForConnected(int msecs, bool *timedOut)
     stopWatch.start();
 
     while (socks5State != wantedState) {
-        if (!data->controlSocket->waitForReadyRead(qt_timeout_value(msecs, stopWatch.elapsed()))) {
+        if (!data->controlSocket->waitForReadyRead(qt_subtract_from_timeout(msecs, stopWatch.elapsed()))) {
             if (data->controlSocket->state() == QAbstractSocket::UnconnectedState)
                 return true;
 
@@ -1774,7 +1762,7 @@ bool QSocks5SocketEngine::waitForRead(int msecs, bool *timedOut)
     if (d->mode == QSocks5SocketEnginePrivate::ConnectMode ||
         d->mode == QSocks5SocketEnginePrivate::BindMode) {
         while (!d->readNotificationActivated) {
-            if (!d->data->controlSocket->waitForReadyRead(qt_timeout_value(msecs, stopWatch.elapsed()))) {
+            if (!d->data->controlSocket->waitForReadyRead(qt_subtract_from_timeout(msecs, stopWatch.elapsed()))) {
                 if (d->data->controlSocket->state() == QAbstractSocket::UnconnectedState)
                     return true;
 
@@ -1787,7 +1775,7 @@ bool QSocks5SocketEngine::waitForRead(int msecs, bool *timedOut)
 #ifndef QT_NO_UDPSOCKET
     } else {
         while (!d->readNotificationActivated) {
-            if (!d->udpData->udpSocket->waitForReadyRead(qt_timeout_value(msecs, stopWatch.elapsed()))) {
+            if (!d->udpData->udpSocket->waitForReadyRead(qt_subtract_from_timeout(msecs, stopWatch.elapsed()))) {
                 setError(d->udpData->udpSocket->error(), d->udpData->udpSocket->errorString());
                 if (timedOut && d->udpData->udpSocket->error() == QAbstractSocket::SocketTimeoutError)
                     *timedOut = true;
@@ -1824,11 +1812,11 @@ bool QSocks5SocketEngine::waitForWrite(int msecs, bool *timedOut)
 
     // flush any bytes we may still have buffered in the time that we have left
     if (d->data->controlSocket->bytesToWrite())
-        d->data->controlSocket->waitForBytesWritten(qt_timeout_value(msecs, stopWatch.elapsed()));
+        d->data->controlSocket->waitForBytesWritten(qt_subtract_from_timeout(msecs, stopWatch.elapsed()));
     while ((msecs == -1 || stopWatch.elapsed() < msecs)
            && d->data->controlSocket->state() == QAbstractSocket::ConnectedState
            && d->data->controlSocket->bytesToWrite() >= MaxWriteBufferSize)
-        d->data->controlSocket->waitForBytesWritten(qt_timeout_value(msecs, stopWatch.elapsed()));
+        d->data->controlSocket->waitForBytesWritten(qt_subtract_from_timeout(msecs, stopWatch.elapsed()));
     return d->data->controlSocket->bytesToWrite() < MaxWriteBufferSize;
 }
 
diff --git a/src/network/ssl/qsslsocket.cpp b/src/network/ssl/qsslsocket.cpp
index c0c15fb5b1..39cd562bc4 100644
--- a/src/network/ssl/qsslsocket.cpp
+++ b/src/network/ssl/qsslsocket.cpp
@@ -301,19 +301,6 @@
 
 QT_BEGIN_NAMESPACE
 
-/*
-   Returns the difference between msecs and elapsed. If msecs is -1,
-   however, -1 is returned.
-*/
-static int qt_timeout_value(int msecs, int elapsed)
-{
-    if (msecs == -1)
-        return -1;
-
-    int timeout = msecs - elapsed;
-    return timeout < 0 ? 0 : timeout;
-}
-
 class QSslSocketGlobalData
 {
 public:
@@ -1518,7 +1505,7 @@ bool QSslSocket::waitForEncrypted(int msecs)
             startClientEncryption();
         // Loop, waiting until the connection has been encrypted or an error
         // occurs.
-        if (!d->plainSocket->waitForReadyRead(qt_timeout_value(msecs, stopWatch.elapsed())))
+        if (!d->plainSocket->waitForReadyRead(qt_subtract_from_timeout(msecs, stopWatch.elapsed())))
             return false;
     }
     return d->connectionEncrypted;
@@ -1562,7 +1549,7 @@ bool QSslSocket::waitForReadyRead(int msecs)
     // test readyReadEmitted first because either operation above
     // (waitForEncrypted or transmit) may have set it
     while (!readyReadEmitted &&
-           d->plainSocket->waitForReadyRead(qt_timeout_value(msecs, stopWatch.elapsed()))) {
+           d->plainSocket->waitForReadyRead(qt_subtract_from_timeout(msecs, stopWatch.elapsed()))) {
     }
 
     d->readyReadEmittedPointer = previousReadyReadEmittedPointer;
@@ -1593,7 +1580,7 @@ bool QSslSocket::waitForBytesWritten(int msecs)
         d->transmit();
     }
 
-    return d->plainSocket->waitForBytesWritten(qt_timeout_value(msecs, stopWatch.elapsed()));
+    return d->plainSocket->waitForBytesWritten(qt_subtract_from_timeout(msecs, stopWatch.elapsed()));
 }
 
 /*!
@@ -1626,7 +1613,7 @@ bool QSslSocket::waitForDisconnected(int msecs)
         if (!waitForEncrypted(msecs))
             return false;
     }
-    bool retVal = d->plainSocket->waitForDisconnected(qt_timeout_value(msecs, stopWatch.elapsed()));
+    bool retVal = d->plainSocket->waitForDisconnected(qt_subtract_from_timeout(msecs, stopWatch.elapsed()));
     if (!retVal) {
         setSocketState(d->plainSocket->state());
         setSocketError(d->plainSocket->error());
diff --git a/tests/auto/other/networkselftest/networkselftest.pro b/tests/auto/other/networkselftest/networkselftest.pro
index c8b870128d..22208e02fb 100644
--- a/tests/auto/other/networkselftest/networkselftest.pro
+++ b/tests/auto/other/networkselftest/networkselftest.pro
@@ -2,7 +2,7 @@ CONFIG += testcase
 TARGET = tst_networkselftest
 
 SOURCES += tst_networkselftest.cpp
-QT = core network testlib
+QT = core core-private network testlib
 
 win32:CONFIG += insignificant_test # QTBUG-27571
 DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0
diff --git a/tests/auto/other/networkselftest/tst_networkselftest.cpp b/tests/auto/other/networkselftest/tst_networkselftest.cpp
index 36c9027aca..5472b74c07 100644
--- a/tests/auto/other/networkselftest/tst_networkselftest.cpp
+++ b/tests/auto/other/networkselftest/tst_networkselftest.cpp
@@ -34,6 +34,7 @@
 #include <QtTest/QtTest>
 #include <QtNetwork/QtNetwork>
 #include <QtCore/QDateTime>
+#include <QtCore/private/qiodevice_p.h>
 
 #ifndef QT_NO_BEARERMANAGEMENT
 #include <QtNetwork/qnetworkconfigmanager.h>
@@ -171,10 +172,11 @@ static bool doSocketRead(QTcpSocket *socket, int minBytesAvailable, int timeout
     forever {
         if (socket->bytesAvailable() >= minBytesAvailable)
             return true;
+        timeout = qt_subtract_from_timeout(timeout, timer.elapsed());
         if (socket->state() == QAbstractSocket::UnconnectedState
-            || timer.elapsed() >= timeout)
+            || timeout == 0)
             return false;
-        if (!socket->waitForReadyRead(timeout - timer.elapsed()))
+        if (!socket->waitForReadyRead(timeout))
             return false;
     }
 }
@@ -202,10 +204,11 @@ static bool doSocketFlush(QTcpSocket *socket, int timeout = 4000)
 #endif
             )
             return true;
+        timeout = qt_subtract_from_timeout(timeout, timer.elapsed());
         if (socket->state() == QAbstractSocket::UnconnectedState
-            || timer.elapsed() >= timeout)
+            || timeout == 0)
             return false;
-        if (!socket->waitForBytesWritten(timeout - timer.elapsed()))
+        if (!socket->waitForBytesWritten(timeout))
             return false;
     }
 }