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From: "Paul E. McKenney" <paulmck@kernel.org>
To: linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org
Cc: elver@google.com,
	akpm@linux-foundation.org,
	tglx@linutronix.de,
	peterz@infradead.org,
	dianders@chromium.org,
	pmladek@suse.com,
	torvalds@linux-foundation.org,
	Arnd Bergmann <arnd@arndb.de>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Yujie Liu <yujie.liu@intel.com>,
	Andi Shyti <andi.shyti@linux.intel.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>
Subject: [PATCH cmpxchg 13/14] xtensa: Emulate one-byte cmpxchg
Date: Mon,  8 Apr 2024 10:49:43 -0700
Message-Id: <20240408174944.907695-13-paulmck@kernel.org>
In-Reply-To: <7b3646e0-667c-48e2-8f09-e493c43c30cb@paulmck-laptop>
References: <7b3646e0-667c-48e2-8f09-e493c43c30cb@paulmck-laptop>
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Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on xtensa.

[ paulmck: Apply kernel test robot feedback. ]
[ paulmck: Drop two-byte support per Arnd Bergmann feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
---
 arch/xtensa/Kconfig               | 1 +
 arch/xtensa/include/asm/cmpxchg.h | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index f200a4ec044e6..d3db28f2f8110 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -14,6 +14,7 @@ config XTENSA
 	select ARCH_HAS_DMA_SET_UNCACHED if MMU
 	select ARCH_HAS_STRNCPY_FROM_USER if !KASAN
 	select ARCH_HAS_STRNLEN_USER
+	select ARCH_NEED_CMPXCHG_1_EMU
 	select ARCH_USE_MEMTEST
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
diff --git a/arch/xtensa/include/asm/cmpxchg.h b/arch/xtensa/include/asm/cmpxchg.h
index 675a11ea8de76..29f8f594d5592 100644
--- a/arch/xtensa/include/asm/cmpxchg.h
+++ b/arch/xtensa/include/asm/cmpxchg.h
@@ -15,6 +15,7 @@
 
 #include <linux/bits.h>
 #include <linux/stringify.h>
+#include <linux/cmpxchg-emu.h>
 
 /*
  * cmpxchg
@@ -74,6 +75,7 @@ static __inline__ unsigned long
 __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
 {
 	switch (size) {
+	case 1:  return cmpxchg_emu_u8((volatile u8 *)ptr, old, new);
 	case 4:  return __cmpxchg_u32(ptr, old, new);
 	default: __cmpxchg_called_with_bad_pointer();
 		 return old;
-- 
2.40.1