diff options
Diffstat (limited to 'arch/arm64/Kconfig')
| -rw-r--r-- | arch/arm64/Kconfig | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index aeecfdac027b..d680ed628c2f 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -205,6 +205,31 @@ config HOTPLUG_CPU If you don't know what to do here, say N. +config SWP_EMULATE + bool "Emulate SWP/SWPB instructions" + help + ARMv6 architecture deprecates use of the SWP/SWPB instructions. ARMv8 + oblosetes the use of 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. + source kernel/Kconfig.preempt config ARCH_NR_GPIO @@ -247,6 +272,7 @@ config HW_PERF_EVENTS config ARMV7_COMPAT bool "Kernel support for ARMv7 applications" depends on COMPAT + select SWP_EMULATE help This option enables features that allow that ran on an ARMv7 or older processor to continue functioning. |