[PATCH v3 rcu 07/11] arch/loongarch: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option

[Paul E. McKenney]

The loongarch architecture uses the atomic read-modify-write amadd
instruction to implement this_cpu_add(), which is NMI safe.  This means
that the old and more-efficient srcu_read_lock() may be used in NMI
context, without the need for srcu_read_lock_nmisafe().  Therefore, add
the new Kconfig option ARCH_HAS_NMI_SAFE_THIS_CPU_OPS to arch/x86/Kconfig,
which will cause NEED_SRCU_NMI_SAFE to be deselected, thus preserving
the current srcu_read_lock() behavior.

Link: https://lore.kernel.org/all/20220910221947.171557773@xxxxxxxxxxxxx/

Suggested-by: Neeraj Upadhyay <quic_neeraju@xxxxxxxxxxx>
Suggested-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Suggested-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Huacai Chen <chenhuacai@xxxxxxxxxx>
Cc: WANG Xuerui <kernel@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: John Ogness <john.ogness@xxxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: <loongarch@xxxxxxxxxxxxxxx>
---
 arch/loongarch/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 903096bd87f88..386adde2feffb 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -10,6 +10,7 @@ config LOONGARCH
 	select ARCH_ENABLE_MEMORY_HOTPLUG
 	select ARCH_ENABLE_MEMORY_HOTREMOVE
 	select ARCH_HAS_ACPI_TABLE_UPGRADE	if ACPI
+	select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_INLINE_READ_LOCK if !PREEMPTION
-- 
2.31.1.189.g2e36527f23