From: Vegard Nossum <vegard.nossum@gmail.com>
Date: Sun, 14 Sep 2008 17:03:53 +0000 (+0200)
Subject: x86: add memory clobber in switch_to()
X-Git-Tag: firefly_0821_release~17719^2~63
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=33f8c40a30ae99e971d068c9ec6088e713c46f5f;p=firefly-linux-kernel-4.4.55.git

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@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/include/asm-x86/system.h b/include/asm-x86/system.h
index 34505dd7b24d..b20c894660f9 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)
 
 /*