[PATCH] uml: mark SMP on UML/x86_64 as broken

Noticed by Al Viro <viro@parcelfarce.linux.theplanet.co.uk> - SMP on x86_64 is
fundamentally broken due to UML's reuse of the host arch's percpu stuff.  This
is OK on x86, but the x86_64 pda stuff just won't work for UML.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 5 insertions, 1 deletions

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index d5e22f084880..684e1f8b2755 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -196,7 +196,7 @@ config HOST_2G_2G
 config SMP
         bool "Symmetric multi-processing support (EXPERIMENTAL)"
         default n
-        depends on MODE_TT && EXPERIMENTAL
+        depends on (MODE_TT && EXPERIMENTAL && !SMP_BROKEN) || (BROKEN && SMP_BROKEN)
         help
         This option enables UML SMP support.
         It is NOT related to having a real SMP box. Not directly, at least.
diff --git a/arch/um/Kconfig.x86_64 b/arch/um/Kconfig.x86_64
index 6e5357c5bcfb..bd35e59419c8 100644
--- a/arch/um/Kconfig.x86_64
+++ b/arch/um/Kconfig.x86_64
@@ -37,3 +37,7 @@ config ARCH_HAS_SC_SIGNALS
 config ARCH_REUSE_HOST_VSYSCALL_AREA
         bool
         default n
+
+config SMP_BROKEN
+        bool
+        default y