From patchwork Thu Sep 29 18:07:29 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 12994535 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 742B4C433F5 for ; Thu, 29 Sep 2022 18:08:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=6tw7MsdtK9+IpcWEo03IcsGAW0DnrOjKiXKNrUDd1TU=; b=XBOQLI4hP8Y4Ne s+NbkQvXMzJJo0aMzh8oD5A+y9noGWXvts7FShKGQx1i3rDNw0Wy7drpEa5aNrdHuUcN4XuG6zavo 8HDP8BZ14G3jhHXuPST36cwC0q7UukAy5IUMy8hsuXghFrHZdFCCaZp9K3bRismIJ05wkVJFyVT73 VAVRmsVetOOzKh0bfJowt97ieuG3gAhJE8/nQTfYNsUdAIVC6YS2DMhmU6pAavxggCJtTxEntF6Zp oK19WWJ7qG4a/MIR2XklzoGZuI2jHit8/ErFL+T5EOgkVoVmaxWfVRrRH868QDf5x4uMYC61uRGPz 112qgLMp5bobThS2fUZA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1odxwg-004qFG-Ao; Thu, 29 Sep 2022 18:07:38 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1odxwd-004qDQ-7W for linux-arm-kernel@lists.infradead.org; Thu, 29 Sep 2022 18:07:36 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8AF1E62130; Thu, 29 Sep 2022 18:07:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5A156C43147; Thu, 29 Sep 2022 18:07:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664474853; bh=mHU3BGDi2Cn8CMLUz7jhHsHdIi9mfBYwtnqDAVqotcQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YaSKjYPOn+yz8mSVCMGYX2izTptjHX5/GeAd+POE96U3AFswPR89dUD4dUQMuVukB HHzOP8f6Eqmu7efu0J7mk7WawsMBmeSs/6mEi8YF81nlsHSUVtssRwyXbCWH2LUyns QcSVy8HEpFH8Ov/bdQ64uxt4vpmc3nS4Rega5HlBfdxQ/ePtCaaUEqZ5jaQ6HPDGQ7 MUFxb2+WKrGexy3PRTKeolYJzAqON0A2sBaxE18yjfOqPmXmhGyDdDEhALJO4cMYgp bL+n/B0p5I2N2PcqkVfB8EMiqhRyaZH4Uft+avQyr38nlCgirtbV1cVrY4bdRf99HF y0CXX2x6a2ZFg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id B4B285C0ED4; Thu, 29 Sep 2022 11:07:32 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, "Paul E. McKenney" , Neeraj Upadhyay , Frederic Weisbecker , Boqun Feng , Catalin Marinas , Will Deacon , Thomas Gleixner , John Ogness , Petr Mladek , linux-arm-kernel@lists.infradead.org Subject: [PATCH RFC v2 rcu 6/8] arch/arm64: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option Date: Thu, 29 Sep 2022 11:07:29 -0700 Message-Id: <20220929180731.2875722-6-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220929180714.GA2874192@paulmck-ThinkPad-P17-Gen-1> References: <20220929180714.GA2874192@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220929_110735_324902_487365C8 X-CRM114-Status: GOOD ( 12.60 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The arm64 architecture uses either an LL/SC loop (old systems) or an LSE stadd instruction (new systems) to implement this_cpu_add(), both of which are NMI safe. This means that the old and more-efficient srcu_read_lock() may be used in NMI context, without the need for srcu_read_lock_nmisafe(). Therefore, add the new Kconfig option ARCH_HAS_NMI_SAFE_THIS_CPU_OPS to arch/arm64/Kconfig, which will cause NEED_SRCU_NMI_SAFE to be deselected, thus preserving the current srcu_read_lock() behavior. Link: https://lore.kernel.org/all/20220910221947.171557773@linutronix.de/ Suggested-by: Neeraj Upadhyay Suggested-by: Frederic Weisbecker Suggested-by: Boqun Feng Signed-off-by: Paul E. McKenney Cc: Catalin Marinas Cc: Will Deacon Cc: Thomas Gleixner Cc: John Ogness Cc: Petr Mladek Cc: --- arch/arm64/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 571cc234d0b3..664725a0b5dd 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -31,6 +31,7 @@ config ARM64 select ARCH_HAS_KCOV select ARCH_HAS_KEEPINITRD select ARCH_HAS_MEMBARRIER_SYNC_CORE + select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE select ARCH_HAS_PTE_DEVMAP select ARCH_HAS_PTE_SPECIAL