FAILED: patch "[PATCH] docs: Makefile: Use CONFIG_SHELL not SHELL" failed to apply to 5.10-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 222a28edce38b62074a950fb243df621c602b4d3 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Thu, 17 Jun 2021 15:58:08 -0700
Subject: [PATCH] docs: Makefile: Use CONFIG_SHELL not SHELL

Fix think-o about which variable to find the Kbuild-configured shell.
This has accidentally worked due to most shells setting $SHELL by
default.

Fixes: 51e46c7a4007 ("docs, parallelism: Rearrange how jobserver reservations are made")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210617225808.3907377-1-keescook@chromium.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/Documentation/Makefile b/Documentation/Makefile
index 9c42dde97671..c3feb657b654 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -76,7 +76,7 @@ quiet_cmd_sphinx = SPHINX  $@ --> file://$(abspath $(BUILDDIR)/$3/$4)
 	PYTHONDONTWRITEBYTECODE=1 \
 	BUILDDIR=$(abspath $(BUILDDIR)) SPHINX_CONF=$(abspath $(srctree)/$(src)/$5/$(SPHINX_CONF)) \
 	$(PYTHON3) $(srctree)/scripts/jobserver-exec \
-	$(SHELL) $(srctree)/Documentation/sphinx/parallel-wrapper.sh \
+	$(CONFIG_SHELL) $(srctree)/Documentation/sphinx/parallel-wrapper.sh \
 	$(SPHINXBUILD) \
 	-b $2 \
 	-c $(abspath $(srctree)/$(src)) \