Module: xenomai-2.6
Branch: master
Commit: 9796a511cc2d360ca655171255a8fdacd65ebba9
URL:
http://git.xenomai.org/?p=xenomai-2.6.git;a=commit;h=9796a511cc2d360ca655171255a8fdacd65ebba9
Author: Gilles Chanteperdrix <gilles.chanteperd...@xenomai.org>
Date: Wed Jun 5 08:03:39 2013 +0200
hal/arm: replace config check with compile check
Starting with Linux 3.8, due to the change in the ASID roll-over mechanism,
we can disable unlocked context switch on SMP platforms, which improves
user-space scheduling latency and may provide a more interesting trade-off
especially since SMP platforms do not flush the cache on mm switch, so have
short mm switch time.
So, replace the Kconfig check that was forcing unlocked context switch on SMP,
with a compile-time check, which takes the kernel version into account.
---
include/asm-arm/wrappers.h | 5 +++++
ksrc/arch/arm/Kconfig | 9 ++-------
2 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/include/asm-arm/wrappers.h b/include/asm-arm/wrappers.h
index b170d3a..6706ff9 100644
--- a/include/asm-arm/wrappers.h
+++ b/include/asm-arm/wrappers.h
@@ -115,4 +115,9 @@ static inline void fp_init(union fp_state *state)
#define CONFIG_XENO_HW_UNLOCKED_SWITCH 1
#endif
+#if defined(CONFIG_SMP) && !defined(CONFIG_XENO_HW_UNLOCKED_SWITCH) && \
+ LINUX_VERSION_CODE < KERNEL_VERSION(3,8,0)
+#error "Xenomai: ARM SMP systems require unlocked context switch prior to
Linux 3.8"
+#endif
+
#endif /* _XENO_ASM_ARM_WRAPPERS_H */
diff --git a/ksrc/arch/arm/Kconfig b/ksrc/arch/arm/Kconfig
index f400faa..ade963a 100644
--- a/ksrc/arch/arm/Kconfig
+++ b/ksrc/arch/arm/Kconfig
@@ -24,11 +24,6 @@ config IPIPE_WANT_PREEMPTIBLE_SWITCH
config IPIPE_WANT_ACTIVE_MM
def_bool y
-config SELECT_HW_UNLOCKED_SWITCH_ON_SMP
- bool
- select XENO_HW_UNLOCKED_SWITCH
- default y if SMP
-
config XENO_HW_FPU
bool "Enable FPU support"
default y
@@ -51,9 +46,9 @@ config XENO_HW_UNLOCKED_SWITCH
This option reduces interrupt latency when costly cache and
TLB flushes are required to switch context, and is mandatory
- on SMP/multi-core systems.
+ on SMP/multi-core systems prior to Linux 3.8.
- You definitely want to enable that option on embedded ARM
+ You definitely want to enable that option on low-end ARM
platforms.
endmenu
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