From patchwork Wed Sep 21 14:46:20 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: 12983798 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A7C91C6FA82 for ; Wed, 21 Sep 2022 14:46:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229767AbiIUOq0 (ORCPT ); Wed, 21 Sep 2022 10:46:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33976 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229498AbiIUOqZ (ORCPT ); Wed, 21 Sep 2022 10:46:25 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C71983BE4; Wed, 21 Sep 2022 07:46:23 -0700 (PDT) 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 ams.source.kernel.org (Postfix) with ESMTPS id 0728EB81A73; Wed, 21 Sep 2022 14:46:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ABD63C433D6; Wed, 21 Sep 2022 14:46:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1663771580; bh=HATBQ0LpiaUjynQ0ce9PLBK2pIPKrRwoKlfyhQ1IDIQ=; h=Date:From:To:Cc:Subject:Reply-To:From; b=aBsYnLVQulIyoPutJzPjFQznHM+fLPIpXMFj+S7R2WMMSMlOVZ219qPjSxZLVU8c6 pW3wlX/2kLhUwrkU5tOZwn+v7fGUhRFniwX9Yh3r2usIcvIM5eTq91i8kVEzK/lNEz Uc0kYtT+/ZY3jixCfgrSOtEDp2ttCXZ/4FimYlLb+p0n6E8EmMVHolG36bxWc/vJOv zK4kwiI/N4D4ku3sCtEepF7vDd1g5ZqWSP9RTW9Mx8XHh6GIcmyAVIVr2xIlK7Loby SC6prARP057q129K35EQVY9PUBDaoCCyZl5Wq6COEtunmCcMKupzQIB7Dt2bZN7tgJ J0tcYk26SeL/Q== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 4D96B5C0849; Wed, 21 Sep 2022 07:46:20 -0700 (PDT) Date: Wed, 21 Sep 2022 07:46:20 -0700 From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, tglx@linutronix.de, john.ogness@linutronix.de, pmladek@suse.com Subject: [PATCH rcu 0/4] NMI-safe SRCU reader API Message-ID: <20220921144620.GA1200846@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org Hello! This RFC series provides an NMI-safe SRCU reader API in the guise of srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe(). A given srcu_struct structure must use either the traditional srcu_read_lock() and srcu_read_unlock() API or the new _nmisafe() API: Mixing and matching is not permitted. So much so that kernels built with CONFIG_PROVE_RCU=y will complain if you try it. The reason for this restriction is that I have yet to find a use case that is not a accident waiting to happen. And if free intermixing were permitted, it is pretty much a given that someone somewhere will get confused and use srcu_read_lock_nmisafe() within NMI handlers and srcu_read_lock() elsewhere, which will not (repeat, NOT) provide NMI safety. The series is as follows: 1. Convert ->srcu_lock_count and ->srcu_unlock_count to atomic. 2. Create and srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe(). 3. Check for consistent per-CPU per-srcu_struct NMI safety. 4. Check for consistent global per-srcu_struct NMI safety. Thanx, Paul ------------------------------------------------------------------------ b/include/linux/srcu.h | 37 ++++++++++++++++++++ b/include/linux/srcutiny.h | 11 ++++++ b/include/linux/srcutree.h | 4 +- b/kernel/rcu/Kconfig | 3 + b/kernel/rcu/rcutorture.c | 11 ++++-- b/kernel/rcu/srcutree.c | 24 ++++++------- include/linux/srcu.h | 4 +- include/linux/srcutiny.h | 4 +- include/linux/srcutree.h | 12 +++++- kernel/rcu/srcutree.c | 82 +++++++++++++++++++++++++++++++++++++++------ 10 files changed, 160 insertions(+), 32 deletions(-)