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[v3,2/5] ARC: Emulate two-byte cmpxchg

Message ID 20260917163830.3748-3-brads@mainlining.org
State New
Headers show
Series [v3,1/5] lib: Add two-byte cmpxchg emulation function | expand

Commit Message

Bradley Morgan Sept. 17, 2026, 4:38 p.m. UTC 
ARC has no two-byte atomic compare and swap, so the __cmpxchg() macro
switch lets case 2 fall through to BUILD_BUG() via default. Route case
2 through the new cmpxchg_emu_u16(), which takes the old and new
values as unsigned long and narrows them itself, so the (uintptr_t)
casts on _o_ and _n_ are no longer needed and the case 2 call passes
them straight.

Signed-off-by: Bradley Morgan <brads@mainlining.org>
---
 arch/arc/include/asm/cmpxchg.h | 3 +++
 1 file changed, 3 insertions(+)
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Patch

diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
index 76f43db0890f..9b48b8fe0db2 100644
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -50,6 +50,9 @@ 
 	case 1:								\
 		_prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *__force)_p_, (uintptr_t)_o_, (uintptr_t)_n_);	\
 		break;							\
+	case 2:								\
+		_prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *__force)_p_, (uintptr_t)_o_, (uintptr_t)_n_);	\
+		break;							\
 	case 4:								\
 		_prev_ = __cmpxchg(_p_, _o_, _n_);			\
 		break;							\