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Message-ID: <20080914170353.GA15729@damson.getinternet.no>
Date: Sun, 14 Sep 2008 19:03:53 +0200
From: Vegard Nossum <vegard.nossum@...il.com>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
Subject: [RFC][PATCH] x86: add memory clobber in switch_to()
There are more places which have segment register reloads without
adding memory clobbers. Should we fix them up? Here's one of them:
>From 5f135687f7730fbdd979b6fb408fd3ca08a0a678 Mon Sep 17 00:00:00 2001
From: Vegard Nossum <vegard.nossum@...il.com>
Date: Sun, 14 Sep 2008 18:53:22 +0200
Subject: [PATCH] x86: add memory clobber in switch_to()
Segment registers are reloaded, so we should add a memory clobber. The
generated assembly code is identical in my tests, but this doesn't mean
it is necessarily true for all configurations/compilers.
x86_64 already has the memory clobber.
Signed-off-by: Vegard Nossum <vegard.nossum@...il.com>
---
include/asm-x86/system.h | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)
diff --git a/include/asm-x86/system.h b/include/asm-x86/system.h
index 983ce37..fed6482 100644
--- a/include/asm-x86/system.h
+++ b/include/asm-x86/system.h
@@ -64,7 +64,10 @@ do { \
\
/* regparm parameters for __switch_to(): */ \
[prev] "a" (prev), \
- [next] "d" (next)); \
+ [next] "d" (next) \
+ \
+ : /* reloaded segment registers */ \
+ "memory"); \
} while (0)
/*
--
1.5.5.1
--
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