Patch "gcov: disable tree-loop-im to reduce stack usage" has been added to the 4.5-stable tree

This is a note to let you know that I've just added the patch titled

gcov: disable tree-loop-im to reduce stack usage

to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
gcov-disable-tree-loop-im-to-reduce-stack-usage.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Arnd Bergmann <[email protected]>
Date: Mon, 25 Apr 2016 17:35:30 +0200
Subject: gcov: disable tree-loop-im to reduce stack usage

From: Arnd Bergmann <[email protected]>

commit c87bf431448b404a6ef5fbabd74c0e3e42157a7f upstream.

Enabling CONFIG_GCOV_PROFILE_ALL produces us a lot of warnings like

lib/lz4/lz4hc_compress.c: In function 'lz4_compresshcctx':
lib/lz4/lz4hc_compress.c:514:1: warning: the frame size of 1504 bytes is larger than 1024 bytes [-Wframe-larger-than=]

After some investigation, I found that this behavior started with gcc-4.9, and opened https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69702.
A suggested workaround for it is to use the -fno-tree-loop-im flag that turns off one of the optimization stages in gcc, so the code runs a little slower but does not use excessive amounts of stack.

We could make this conditional on the gcc version, but I could not find an easy way to do this in Kbuild and the benefit would be fairly small, given that most of the gcc version in production are affected now.

I'm marking this for 'stable' backports because it addresses a bug with code generation in gcc that exists in all kernel versions with the affected gcc releases.

---
 Makefile |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -364,7 +364,7 @@ AFLAGS_MODULE   =
 LDFLAGS_MODULE  =
 CFLAGS_KERNEL	=
 AFLAGS_KERNEL	=
-CFLAGS_GCOV	= -fprofile-arcs -ftest-coverage
+CFLAGS_GCOV	= -fprofile-arcs -ftest-coverage -fno-tree-loop-im
 
 
 # Use USERINCLUDE when you must reference the UAPI directories only.

Patches currently in stable-queue which might be from [email protected] are

queue-4.5/gcov-disable-tree-loop-im-to-reduce-stack-usage.patch