[rtems-docs commit] c-user: Clarify rtems_extension_create()

[Sebastian Huber]

Module:    rtems-docs
Branch:    master
Commit:    0bc62eee950008a2e3b4eb8c5a4f8f4cf39473e1
Changeset: http://git.rtems.org/rtems-docs/commit/?id=0bc62eee950008a2e3b4eb8c5a4f8f4cf39473e1

Author:    Sebastian Huber <sebastian.huber at embedded-brains.de>
Date:      Tue Sep 14 08:15:25 2021 +0200

c-user: Clarify rtems_extension_create()

---

 c-user/user-extensions/directives.rst | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/c-user/user-extensions/directives.rst b/c-user/user-extensions/directives.rst
index 2dbac54..ac04cdd 100644
--- a/c-user/user-extensions/directives.rst
+++ b/c-user/user-extensions/directives.rst
@@ -102,11 +102,15 @@ The extension set is initialized using the extension table specified in
 
 .. rubric:: NOTES:
 
-The user-provided extension set table is not used after the return of the
+The user-provided extension table is not used after the return of the
 directive.
 
-Newly created extension sets are immediately installed and are invoked upon the
-next system event supporting an extension.
+Each extension of the extension table is optional and may be `NULL
+<https://en.cppreference.com/w/c/types/NULL>`_.  All extensions except the task
+switch extension of the extension table are atomically and immediately
+installed.  A task switch extension is separately installed after the other
+extensions.  The extensions of the extension table are invoked upon the next
+system event supporting an extension.
 
 An alternative to dynamically created extension sets are initial extensions,
 see :ref:`CONFIGURE_INITIAL_EXTENSIONS`.  Initial extensions are recommended