1 files changed, 35 insertions, 3 deletions
diff --git a/poky/documentation/ref-manual/tasks.rst b/poky/documentation/ref-manual/tasks.rst
index 0db960b22f..c28cd7a94a 100644
--- a/poky/documentation/ref-manual/tasks.rst
+++ b/poky/documentation/ref-manual/tasks.rst
@@ -470,9 +470,29 @@ You can run this task using BitBake as follows::
 
    $ bitbake -c cleanall recipe
 
-Typically, you would not normally use the :ref:`ref-tasks-cleanall` task. Do so only
-if you want to start fresh with the :ref:`ref-tasks-fetch`
-task.
+You should never use the :ref:`ref-tasks-cleanall` task in a normal
+scenario. If you want to start fresh with the :ref:`ref-tasks-fetch` task,
+use instead::
+
+  $ bitbake -f -c fetch recipe
+
+.. note::
+
+   The reason to prefer ``bitbake -f -c fetch`` is that the
+   :ref:`ref-tasks-cleanall` task would break in some cases, such as::
+
+      $ bitbake -c fetch    recipe
+      $ bitbake -c cleanall recipe-native
+      $ bitbake -c unpack   recipe
+
+   because after step 1 there is a stamp file for the
+   :ref:`ref-tasks-fetch` task of ``recipe``, and it won't be removed at
+   step 2 because step 2 uses a different work directory. So the unpack task
+   at step 3 will try to extract the downloaded archive and fail as it has
+   been deleted in step 2.
+
+   Note that this also applies to BitBake from concurrent processes when a
+   shared download directory (:term:`DL_DIR`) is setup.
 
 .. _ref-tasks-cleansstate:
 
@@ -496,6 +516,18 @@ scratch is guaranteed.
 
 .. note::
 
+   Using :ref:`ref-tasks-cleansstate` with a shared :term:`SSTATE_DIR` is
+   not recommended because it could trigger an error during the build of a
+   separate BitBake instance. This is because the builds check sstate "up
+   front" but download the files later, so it if is deleted in the
+   meantime, it will cause an error but not a total failure as it will
+   rebuild it.
+
+   The reliable and preferred way to force a new build is to use ``bitbake
+   -f`` instead.
+
+.. note::
+
    The :ref:`ref-tasks-cleansstate` task cannot remove sstate from a remote sstate
    mirror. If you need to build a target from scratch using remote mirrors, use
    the "-f" option as follows::