This is a note to let you know that I've just added the patch titled
arm64: Remove redundant mov from LL/SC cmpxchg
to the 4.9-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:
arm64-remove-redundant-mov-from-ll-sc-cmpxchg.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Mar 4 02:49:26 PM CET 2021
From: Robin Murphy <robin.murphy@xxxxxxx>
Date: Fri, 12 May 2017 13:48:41 +0100
Subject: arm64: Remove redundant mov from LL/SC cmpxchg
From: Robin Murphy <robin.murphy@xxxxxxx>
commit 8df728e1ae614f592961e51f65d3e3212ede5a75 upstream.
The cmpxchg implementation introduced by commit c342f78217e8 ("arm64:
cmpxchg: patch in lse instructions when supported by the CPU") performs
an apparently redundant register move of [old] to [oldval] in the
success case - it always uses the same register width as [oldval] was
originally loaded with, and is only executed when [old] and [oldval] are
known to be equal anyway.
The only effect it seemingly does have is to take up a surprising amount
of space in the kernel text, as removing it reveals:
text data bss dec hex filename
12426658 1348614 4499749 18275021 116dacd vmlinux.o.new
12429238 1348614 4499749 18277601 116e4e1 vmlinux.o.old
Reviewed-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/include/asm/atomic_ll_sc.h | 1 -
1 file changed, 1 deletion(-)
--- a/arch/arm64/include/asm/atomic_ll_sc.h
+++ b/arch/arm64/include/asm/atomic_ll_sc.h
@@ -264,7 +264,6 @@ __LL_SC_PREFIX(__cmpxchg_case_##name(vol
" st" #rel "xr" #sz "\t%w[tmp], %" #w "[new], %[v]\n" \
" cbnz %w[tmp], 1b\n" \
" " #mb "\n" \
- " mov %" #w "[oldval], %" #w "[old]\n" \
"2:" \
: [tmp] "=&r" (tmp), [oldval] "=&r" (oldval), \
[v] "+Q" (*(unsigned long *)ptr) \
Patches currently in stable-queue which might be from robin.murphy@xxxxxxx are
queue-4.9/arm64-cmpxchg-use-k-instead-of-l-for-ll-sc-immediate-constraint.patch
queue-4.9/arm64-remove-redundant-mov-from-ll-sc-cmpxchg.patch
