[PATCH 11/15] ARM: HAVE_VIRT_CPU_ACCOUNTING_GEN requires cmpxchg64

[Arnd Bergmann]

The cpu time accounting code uses 64-bit nanosecond based
cputime_t if HAVE_VIRT_CPU_ACCOUNTING_GEN is enabled, which
in turn requires working cmpxchg64 support. Trying this
on ARMv7M, ARMv5 and earlier, or OABI will result in a
build error like

  CC      kernel/sched/cputime.o
/tmp/ccVoXzRS.s:127: Error: selected processor does not support Thumb mode `ldrexd r4,r5,[r3]'
/tmp/ccVoXzRS.s:131: Error: selected processor does not support Thumb mode `strexd lr,r8,r9,[r3]'
/tmp/ccVoXzRS.s:148: Error: selected processor does not support Thumb mode `ldrexd r6,r7,[r5]'
/tmp/ccVoXzRS.s:152: Error: selected processor does not support Thumb mode `strexd r4,r0,r1,[r5]'

To work around this problem, make HAVE_VIRT_CPU_ACCOUNTING_GEN
depend on the newer architectures and EABI support. There is
very little use in this feature on older machines, so there
should be no downsides.

Signed-off-by: Arnd Bergmann <arnd at arndb.de>
---
 arch/arm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 11cc5fa40ff7..04af434c11b1 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -68,7 +68,7 @@ config ARM
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_UID16
-	select HAVE_VIRT_CPU_ACCOUNTING_GEN
+	select HAVE_VIRT_CPU_ACCOUNTING_GEN if AEABI && (CPU_V6K || CPU_V7)
 	select IRQ_FORCED_THREADING
 	select MODULES_USE_ELF_REL
 	select NO_BOOTMEM
-- 
2.1.0.rc2