From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-m16.yeah.net (mail-m16.yeah.net [1.95.21.15]) (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 78FE538238D for ; Wed, 15 Jul 2026 14:32:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=1.95.21.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784125962; cv=none; b=RW21HCHHhWhQGx0sVGlHidsWoHwlz41dIyexoWnAUoWrNYUrfSVhMvGLuHRZlsJNRrUR8gt1qoty4upnPdQUoHh+Y4yeYnjBdGWxxHQwi2vnaM6CkNUXwvb6It93Si1W32S5PVIiOhvR61c/e2UAex1PlnloHBktH0zay0kFDpM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784125962; c=relaxed/simple; bh=VQJ/dWnqCuRiwa+XC1NAtnl0IHVfbDAMbLJMj/rY9Dg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PV4ZE+gmt5fhi4D2HpOMklpvOpnqIAtRENKNAm+FQlLSm8WC4Wb1NrFhpr8VIB3QsyprBHB50rdc7tjOkZQGKYX2+KixF0y3UhkXthOKXreuDTK+70R1IURDUNx/1ziyZNHNQ03yQDMqOJ7m1wco2MpUmvy5+87mVxD7lGEmATY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=yeah.net; spf=pass smtp.mailfrom=yeah.net; dkim=pass (1024-bit key) header.d=yeah.net header.i=@yeah.net header.b=O4dpv63X; arc=none smtp.client-ip=1.95.21.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=yeah.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=yeah.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=yeah.net header.i=@yeah.net header.b="O4dpv63X" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yeah.net; s=s110527; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=07 L2Pw1amWN/ZraAxhUsQYiZzTO6y6iuj4IDyBGf1w8=; b=O4dpv63XMklVSiiCxj 8tTKXjDlKCE0DtSMH78rJQXsQZsmRx0ko1C1NltkSFp2Z9tPepjIXHR75OgOwlmF BD6S8gRxAXoXQ+dICHDq/4Wb0jan1fCvPN8nwM6R4HnpkFi3K5ooIhXEx2mrRgzS Jq24bIBq4+HznJV/g5OOCODx8= Received: from deepin (unknown []) by gzsmtp3 (Coremail) with UTF8SMTPSA id M88vCgD3H1uImVdq6PNmBA--.40896S4; Wed, 15 Jul 2026 22:30:52 +0800 (CST) From: Ziran Zhang To: Gary Guo Cc: Will Deacon , Peter Zijlstra , Boqun Feng , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , x86@kernel.org, Mark Rutland , linux-kernel@vger.kernel.org, Ziran Zhang Subject: Re: [PATCH] x86/atomic: Add arch_atomic_not() Date: Wed, 15 Jul 2026 22:30:24 +0800 Message-ID: <20260715143025.18489-1-zhangcoder@yeah.net> X-Mailer: git-send-email 2.51.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:M88vCgD3H1uImVdq6PNmBA--.40896S4 X-Coremail-Antispam: 1Uf129KBjvdXoW7Xr18KrWftFWUJFWxAF4Utwb_yoWxKrg_CF 1fG3ykCry5tr4Sqan5Ga1SvFyagrsIqry5W3yDJrySva4kKayjkF4DurnIvrnrGrW8ZF4Y 9r1kXrWFyw43WjkaLaAFLSUrUUUUjb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUvcSsGvfC2KfnxnUUI43ZEXa7xR_UUUUUUUUU== X-CM-SenderInfo: x2kd0wpfrgv2o61htxgoqh3/1tbiIRz9vmpXmZxp5QAA3K On Wed, 15 Jul 2026 12:49:20 +0100, Gary Guo wrote: > > The kernel already has non-atomic bitmap_complement(), but > > no direct atomic implementation. > > > > According to Intel and AMD manuals, the NOT instruction > > supports a LOCK prefix. > > > > Currently the only way to achieve this is arch_atomic_xor(-1, v), > > which is non-obvious and hurts readability, so add arch_atomic_not() > > to provide an explicit atomic complement operation. > > What do you need this for? > > Best, > Gary Hi Gary, At present there is no code in kernel that would call arch_atomic_not() or arch_atomic_xor(~0,v). I'll drop this patch and revisit if a real use case shows up in the future. Thanks for the review! Regards, Ziran Zhang