[PATCH v2 06/22] alpha: select ARCH_SUPPORTS_ATOMIC_RMW

[Matt Turner]

Alpha has native LL/SC instructions (LDL_L/STL_C, LDQ_L/STQ_C) that
provide atomic read-modify-write capability, and already selects
ARCH_HAVE_NMI_SAFE_CMPXCHG.

Selecting ARCH_SUPPORTS_ATOMIC_RMW enables MUTEX_SPIN_ON_OWNER and
RWSEM_SPIN_ON_OWNER on SMP, allowing optimistic spinning on contended
locks rather than immediately sleeping.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@xxxxxxxxx>
Tested-by: Magnus Lindholm <linmag7@xxxxxxxxx>
Reviewed-by: Magnus Lindholm <linmag7@xxxxxxxxx>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 032c23f979c4..d039b7135d18 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -14,6 +14,7 @@ config ALPHA
 	select ARCH_MODULE_NEEDS_WEAK_PER_CPU if SMP
 	select ARCH_NO_PREEMPT
 	select ARCH_NO_SG_CHAIN
+	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select FORCE_PCI
 	select PCI_DOMAINS if PCI

-- 
2.54.0