From: Russell King Date: Fri, 4 Jul 2014 13:44:36 +0000 (+0100) Subject: ARM: SWP emulation: always enable when SMP is enabled X-Git-Tag: v3.17-rc1~117^2~1^2~2 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=a11dd731f5ead63ab3d757bbb1ab631063f6c034;p=linux.git ARM: SWP emulation: always enable when SMP is enabled SWP is deprecated in ARMv6 and ARMv7 CPUs, but more importantly, when running on a SMP system, SWP doesn't guarantee atomicity. This means it can't really be used (by userspace) for locking purposes in a SMP environment. Currently, many configurations leave the SWP emulation disabled, which means we never know if userspace executes this instruction on ARMv7 hardware. Rectify this by enabling SWP emulation for ARMv7 with SMP (where we can trap the instruction.) Tested-by: Tony Lindgren Acked-by: Catalin Marinas Signed-off-by: Russell King --- diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index c348eaee7ee2..c78c7db6aa83 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -669,7 +669,7 @@ config ARM_VIRT_EXT details. config SWP_EMULATE - bool "Emulate SWP/SWPB instructions" + bool "Emulate SWP/SWPB instructions" if !SMP depends on CPU_V7 default y if SMP select HAVE_PROC_CPU if PROC_FS