linux-kernel - [PATCH v6 9/9] powerpc/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS

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Date:   Wed, 31 Mar 2021 14:30:40 +0000
From:   guoren@...nel.org
To:     guoren@...nel.org
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-csky@...r.kernel.org, linux-arch@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-xtensa@...ux-xtensa.org,
        openrisc@...ts.librecores.org, sparclinux@...r.kernel.org,
        Guo Ren <guoren@...ux.alibaba.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Subject: [PATCH v6 9/9] powerpc/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32

From: Guo Ren <guoren@...ux.alibaba.com>

We don't have native hw xchg16 instruction, so let qspinlock
generic code to deal with it.

Using the full-word atomic xchg instructions implement xchg16 has
the semantic risk for atomic operations.

This patch cancels the dependency of on qspinlock generic code on
architecture's xchg16.

Also no need when PPC_LBARX_LWARX is enabled, see the link below.

Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
Link: https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20201107032328.2454582-1-npiggin@gmail.com/
Cc: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
---
 arch/powerpc/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 386ae12d8523..6133ad51690e 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -151,6 +151,7 @@ config PPC
 	select ARCH_USE_CMPXCHG_LOCKREF		if PPC64
 	select ARCH_USE_QUEUED_RWLOCKS		if PPC_QUEUED_SPINLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS	if PPC_QUEUED_SPINLOCKS
+	select ARCH_USE_QUEUED_SPINLOCKS_XCHG32	if PPC_QUEUED_SPINLOCKS && !PPC_LBARX_LWARX
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 	select ARCH_WANT_LD_ORPHAN_WARN
-- 
2.17.1