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>

1 files changed, 4 insertions, 1 deletions

diff --git a/include/asm-x86/system.h b/include/asm-x86/system.h
index 34505dd7b24..b20c894660f 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)
 
 /*