[PATCH] ARM: 2664/2: add support for atomic ops on pre-ARMv6 SMP systems

Patch from Nicolas Pitre

Not that there might be many of them on the planet, but at least RMK
apparently has one.

Signed-off-by: Nicolas Pitre
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index ade0e2222f59..3fefb43c67f7 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -422,3 +422,11 @@ config HAS_TLS_REG
           assume directly accessing that register and always obtain the
           expected value only on ARMv7 and above.
 
+config NEEDS_SYSCALL_FOR_CMPXCHG
+        bool
+        default y if SMP && (CPU_32v5 || CPU_32v4 || CPU_32v3)
+        help
+          SMP on a pre-ARMv6 processor?  Well OK then.
+          Forget about fast user space cmpxchg support.
+          It is just not possible.
+