[PATCH v10 05/11] arm64: add support for poll_idle()

[Ankur Arora <ankur.a.arora@oracle.com>]

Polling in idle helps reduce the cost of remote wakeups: if the target
sets TIF_POLLING_NRFLAG (as it does while polling in idle), the scheduler
can do remote wakeups just by setting the TIF_NEED_RESCHED.

This contrasts with sending an IPI, and incurring the cost of handling
the cost of the interrupt on the receiver.

Enabling poll_idle() needs a cheap mechanism to do the actual polling
(via smp_cond_load_relaxed_timewait()) and TIF_POLLING_NRFLAG support.

arm64 has both of these. So, select ARCH_HAS_OPTIMIZED_POLL.

Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 100570a048c5..d96a6c6d8894 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -39,6 +39,7 @@ config ARM64
 	select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
 	select ARCH_HAS_NONLEAF_PMD_YOUNG if ARM64_HAFT
+	select ARCH_HAS_OPTIMIZED_POLL
 	select ARCH_HAS_PTE_DEVMAP
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_HW_PTE_YOUNG
-- 
2.43.5