From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.mainlining.org (mail.mainlining.org [5.75.144.95]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 27F704CCDF0; Fri, 11 Sep 2026 19:28:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=5.75.144.95 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789154905; cv=none; b=omRfBEo+j/iC573mY5TTvlgQllKEGrVKtXVS0Z3DB2VbE69TLUkSuWHoXVCaZrzJA+WfyzUydjkSv+ipuDLkVwe5ajvqwdTkbKyzFG9xCP2FhH/c/DxhfQpG9czTCDTdc9uquLwl6lcl4aASLPBuZKhGPrIeOq/IWMdCfV2CJ8A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789154905; c=relaxed/simple; bh=C/hHoeoyZgl/552acrQr1Xi0twY+CEaGiAmnrc7FhVE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qAjF8vjXyHr6cvoZ60hMR/QqLTHdC2z0bt8N455lM0Q9aeqdnFD5fDs8FJK+47HwxGZwN/RRrA1SazQHGbYqLOmTskVg/up2C47Znj1n/R0Qo7YTF1o9Gf/l6KoRPH6hQjUNE8gpww4pxIoDTEmDF66xrxlmfzLkIjRB0WMMx5s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mainlining.org; spf=pass smtp.helo=mail.mainlining.org; arc=none smtp.client-ip=5.75.144.95 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mainlining.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.helo=mail.mainlining.org From: Bradley Morgan To: "Paul E. McKenney" Cc: frederic@kernel.org, neeraj.upadhyay@kernel.org, boqun@kernel.org, joelagnelf@nvidia.com, rcu@vger.kernel.org, "Andrew Morton" , "Arnd Bergmann" , linux-arch@vger.kernel.org, "Vineet Gupta" , linux-snps-arc@lists.infradead.org, "Russell King" , linux-arm-kernel@lists.infradead.org, "Guo Ren" , linux-csky@vger.kernel.org, "Yoshinori Sato" , "Rich Felker" , "John Paul Adrian Glaubitz" , linux-sh@vger.kernel.org, "Chris Zankel" , "Max Filippov" , linux-kernel@vger.kernel.org, brads@mainlining.org Subject: [PATCH 2/6] ARC: Emulate two-byte cmpxchg Date: Fri, 11 Sep 2026 19:25:35 +0000 Message-ID: <20260911192540.20983-3-brads@mainlining.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260911192540.20983-1-brads@mainlining.org> References: <20260911192540.20983-1-brads@mainlining.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit arc has no byte or halfword atomic memory operations, so the LLSC arch_cmpxchg_relaxed() switch routes case 1 through cmpxchg_emu_u8() and leaves case 2 to fall into the BUILD_BUG() default. Route case 2 through the new cmpxchg_emu_u16() instead. The !CONFIG_ARC_HAS_LLSC arch_cmpxchg() already handles any size, reading and writing through the typed pointer under the atomic_ops lock, so it needs no change. Signed-off-by: Bradley Morgan --- arch/arc/include/asm/cmpxchg.h | 3 +++ 1 file changed, 3 insertions(+) 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; \ -- 2.47.3