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-rw-r--r--arch/arm/mm/Kconfig27
1 files changed, 27 insertions, 0 deletions
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 6d05f79a8cd2..8493ed04797a 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -636,6 +636,33 @@ config ARM_THUMBEE
Say Y here if you have a CPU with the ThumbEE extension and code to
make use of it. Say N for code that can run on CPUs without ThumbEE.
+config SWP_EMULATE
+ bool "Emulate SWP/SWPB instructions"
+ depends on CPU_V7
+ select HAVE_PROC_CPU if PROC_FS
+ default y if SMP
+ help
+ ARMv6 architecture deprecates use of the SWP/SWPB instructions.
+ ARMv7 multiprocessing extensions introduce the ability to disable
+ these instructions, triggering an undefined instruction exception
+ when executed. Say Y here to enable software emulation of these
+ instructions for userspace (not kernel) using LDREX/STREX.
+ Also creates /proc/cpu/swp_emulation for statistics.
+
+ In some older versions of glibc [<=2.8] SWP is used during futex
+ trylock() operations with the assumption that the code will not
+ be preempted. This invalid assumption may be more likely to fail
+ with SWP emulation enabled, leading to deadlock of the user
+ application.
+
+ NOTE: when accessing uncached shared regions, LDREX/STREX rely
+ on an external transaction monitoring block called a global
+ monitor to maintain update atomicity. If your system does not
+ implement a global monitor, this option can cause programs that
+ perform SWP operations to uncached memory to deadlock.
+
+ If unsure, say Y.
+
config CPU_BIG_ENDIAN
bool "Build big-endian kernel"
depends on ARCH_SUPPORTS_BIG_ENDIAN