linux-kernel - [PATCH] arch: um/x86: Select ARCH_SUPPORTS_ATOMIC_RMW for UML

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Message-ID: <20260106034034.60074-1-boqun.feng@gmail.com>
Date: Tue,  6 Jan 2026 11:40:34 +0800
From: Boqun Feng <boqun.feng@...il.com>
To: linux-um@...ts.infradead.org,
	x86@...nel.org
Cc: Richard Weinberger <richard@....at>,
	Anton Ivanov <anton.ivanov@...bridgegreys.com>,
	Johannes Berg <johannes@...solutions.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org,
	FUJITA Tomonori <fujita.tomonori@...il.com>
Subject: [PATCH] arch: um/x86: Select ARCH_SUPPORTS_ATOMIC_RMW for UML_X86

x86 atomic instructions are used for um on UML_X86, therefore atomics
on UML_X86 support native atomic RmW as x86 does, hence select
ARCH_SUPPORTS_ATOMIC_RMW.

Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
UM & x86 maintainers,

I need this to avoid a build error for Rust atomics since Rust currently
only support Atomic<i8/i16> on ARCH_SUPPORTS_ATOMIC_RMW archs. I will
add it to my upcoming PR if I get some Acked-by, thanks!

 arch/x86/um/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
index bdd7c8e39b01..44b12e45f9a0 100644
--- a/arch/x86/um/Kconfig
+++ b/arch/x86/um/Kconfig
@@ -9,6 +9,7 @@ endmenu
 config UML_X86
 	def_bool y
 	select ARCH_USE_QUEUED_RWLOCKS
+	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_USE_QUEUED_SPINLOCKS
 	select DCACHE_WORD_ACCESS
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS
-- 
2.51.0