Doc: state that models are not thread-safe

Fixes: QTBUG-107598
Pick-to: 6.5 6.2 5.15
Change-Id: I0e7ea8d4b2094d92b3cad5eec5b30e6e3ac64018
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit ccda3362464bfaff999b739aa81925c7b51075a9)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/doc/src/includes/models.qdocinc

@@ -0,0 +1,14 @@
+//! [thread-safety-section1]
+\section1 Thread safety
+
+Being a \l {Accessing QObject Subclasses from Other Threads}{subclass of
+QObject}, \1 is not \l {Reentrancy and Thread-Safety}{thread-safe}. Any \1
+model-related API should only be called from the thread the model object lives
+in. If the \1 is connected with a view, that means the GUI thread, as that is
+where the view lives, and it will call into the model from the GUI thread.
+Using a background thread to populate or modify the contents of a model is
+possible, but requires care, as the background thread cannot call any
+model-related API directly. Instead, you should queue the updates and apply
+them in the main thread. This can be done with \l {Signals and Slots Across
+Threads}{queued connections}.
+//! [thread-safety-section1]

src/corelib/itemmodels/qabstractitemmodel.cpp

@@ -1499,6 +1499,8 @@ void QAbstractItemModel::resetInternalData()
     rows to the model, \l{QAbstractItemModel::}{beginInsertRows()} and
     \l{QAbstractItemModel::}{endInsertRows()} must be called.
 
+    \include models.qdocinc {thread-safety-section1}{QAbstractItemModel}
+
     \sa {Model Classes}, {Model Subclassing Reference}, QModelIndex,
         QAbstractItemView, {Using drag and drop with item views},
         {Simple Tree Model Example}, {Editable Tree Model Example},
@@ -3730,7 +3732,7 @@ void QAbstractItemModel::multiData(const QModelIndex &index, QModelRoleDataSpan
     \note Some general guidelines for subclassing models are available in the
     \l{Model Subclassing Reference}.
 
-    \note
+    \include models.qdocinc {thread-safety-section1}{QAbstractTableModel}
 
     \sa {Model Classes}, QAbstractItemModel, QAbstractListModel
 */