arch/loongarch: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option

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/loongarch/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@linutronix.de/
Suggested-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Suggested-by: Frederic Weisbecker <frederic@kernel.org>
Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>
Cc: <loongarch@lists.linux.dev>

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 903096bd87f8829273a0f7bba4134d3f4c468825..386adde2feffb31f024d4014311baf519dca03bd 100644 (file)
--- 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