From 30bea611df2d95b53b63273ac867d9bd0a181edf Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Sat, 11 Aug 2012 16:45:14 +0200
Subject: Make QBasicMutex be exclusively non-recursive

Dispatch to the recursive mutex functions from QMutex::lock, tryLock
and unlock.

This has the benefit that those using QBasicMutex will not go through
the testing for recursive mutexes. It simplifies a little the code for
those users.

For the users of QMutex, the code required to perform a lock does not
appear to change.

Change-Id: I0ca9965e012b283c30f1fab8e9f6d9b3288c2247
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
---
 src/corelib/thread/qmutex.cpp | 60 ++++++++++++++++++++++++++++---------------
 1 file changed, 40 insertions(+), 20 deletions(-)

(limited to 'src/corelib/thread/qmutex.cpp')

diff --git a/src/corelib/thread/qmutex.cpp b/src/corelib/thread/qmutex.cpp
index fa4fddca56..2906a5a198 100644
--- a/src/corelib/thread/qmutex.cpp
+++ b/src/corelib/thread/qmutex.cpp
@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
+** Copyright (C) 2012 Intel Corporation
 ** Contact: http://www.qt-project.org/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -55,6 +56,19 @@
 
 QT_BEGIN_NAMESPACE
 
+static inline bool isRecursive(QMutexData *d)
+{
+    register quintptr u = quintptr(d);
+    if (Q_LIKELY(u <= 0x3))
+        return false;
+#ifdef QT_LINUX_FUTEX
+    Q_ASSERT(d->recursive);
+    return true;
+#else
+    return d->recursive;
+#endif
+}
+
 /*
     \class QBasicMutex
     \inmodule QtCore
@@ -180,7 +194,13 @@ QMutex::~QMutex()
 */
 void QMutex::lock() QT_MUTEX_LOCK_NOEXCEPT
 {
-    QBasicMutex::lock();
+    if (fastTryLock())
+        return;
+    QMutexData *current = d_ptr.loadAcquire();
+    if (QT_PREPEND_NAMESPACE(isRecursive)(current))
+        static_cast<QRecursiveMutexPrivate *>(current)->lock(-1);
+    else
+        lockInternal();
 }
 
 /*! \fn bool QMutex::tryLock(int timeout)
@@ -208,7 +228,13 @@ void QMutex::lock() QT_MUTEX_LOCK_NOEXCEPT
 */
 bool QMutex::tryLock(int timeout) QT_MUTEX_LOCK_NOEXCEPT
 {
-    return QBasicMutex::tryLock(timeout);
+    if (fastTryLock())
+        return true;
+    QMutexData *current = d_ptr.loadAcquire();
+    if (QT_PREPEND_NAMESPACE(isRecursive)(current))
+        return static_cast<QRecursiveMutexPrivate *>(current)->lock(timeout);
+    else
+        return lockInternal(timeout);
 }
 
 /*! \fn void QMutex::unlock()
@@ -220,7 +246,13 @@ bool QMutex::tryLock(int timeout) QT_MUTEX_LOCK_NOEXCEPT
 */
 void QMutex::unlock() Q_DECL_NOTHROW
 {
-    QBasicMutex::unlock();
+    if (fastTryUnlock())
+        return;
+    QMutexData *current = d_ptr.loadAcquire();
+    if (QT_PREPEND_NAMESPACE(isRecursive)(current))
+        static_cast<QRecursiveMutexPrivate *>(current)->unlock();
+    else
+        unlockInternal();
 }
 
 /*!
@@ -230,16 +262,9 @@ void QMutex::unlock() Q_DECL_NOTHROW
     Returns true if the mutex is recursive
 
 */
-bool QBasicMutex::isRecursive() {
-    QMutexData *d = d_ptr.load();
-    if (quintptr(d) <= 0x3)
-        return false;
-#ifdef QT_LINUX_FUTEX
-    Q_ASSERT(d->recursive);
-    return true;
-#else
-    return d->recursive;
-#endif
+bool QBasicMutex::isRecursive()
+{
+    return QT_PREPEND_NAMESPACE(isRecursive)(d_ptr.loadAcquire());
 }
 
 
@@ -338,8 +363,7 @@ bool QBasicMutex::isRecursive() {
  */
 bool QBasicMutex::lockInternal(int timeout) QT_MUTEX_LOCK_NOEXCEPT
 {
-    if (isRecursive())
-        return static_cast<QRecursiveMutexPrivate *>(d_ptr.load())->lock(timeout);
+    Q_ASSERT(!isRecursive());
 
     while (!fastTryLock()) {
         QMutexData *copy = d_ptr.loadAcquire();
@@ -435,11 +459,7 @@ void QBasicMutex::unlockInternal() Q_DECL_NOTHROW
     QMutexData *copy = d_ptr.loadAcquire();
     Q_ASSERT(copy); //we must be locked
     Q_ASSERT(copy != dummyLocked()); // testAndSetRelease(dummyLocked(), 0) failed
-
-    if (copy->recursive) {
-        static_cast<QRecursiveMutexPrivate *>(copy)->unlock();
-        return;
-    }
+    Q_ASSERT(!isRecursive());
 
     QMutexPrivate *d = reinterpret_cast<QMutexPrivate *>(copy);
 
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