From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B48BBC433FF for ; Mon, 29 Jul 2019 15:24:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E6DC21842 for ; Mon, 29 Jul 2019 15:24:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="NEamSqOt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388023AbfG2PYm (ORCPT ); Mon, 29 Jul 2019 11:24:42 -0400 Received: from merlin.infradead.org ([205.233.59.134]:47632 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387693AbfG2PYl (ORCPT ); Mon, 29 Jul 2019 11:24:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=FZx89eZZ1cBDWZtSjJDEcEp5nFP6/pPHiWDDeTBCfTQ=; b=NEamSqOt48WRoVpCxOh3/8dAG WK6u8E+U0XGi+29bUCas9/PJV88ERYN99TwdcLcCpKfjLzLqrDM8FdSx/dTIlB2Ing2wOMyoLFjWn O6mAt5DIepAlznjW+8hEOqoiEaeK6PhXdb2HCHz4pfVSTEs6FMylJTYdzxnkV/Sukg+Av5Qro6FYq o0id/pAs8wRem/+ipiqiWLAjB+dw/52cXSb22+/uY53njU52OY/4QW3Ioe02/p1UWOpaOu1Ya/XfG 50sBtZKx+vHul9PmG3i6d9GVwwgmX9Jeskujp+zNWUanH30zVG23FpIT4fovM+0+D2nOZ+HlrSlUw GMs4YIWkw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hs7Vl-0003Ua-SO; Mon, 29 Jul 2019 15:24:30 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A15AB20B00021; Mon, 29 Jul 2019 17:24:28 +0200 (CEST) Date: Mon, 29 Jul 2019 17:24:28 +0200 From: Peter Zijlstra To: Andrea Parri Cc: Will Deacon , linux-kernel@vger.kernel.org, Jan Stancek , Waiman Long , dbueso@suse.de, mingo@redhat.com, jade.alglave@arm.com, paulmck@linux.vnet.ibm.com Subject: Re: [PATCH 1/4] locking/rwsem: Add missing ACQUIRE to read_slowpath exit when queue is empty Message-ID: <20190729152428.GH31398@hirez.programming.kicks-ass.net> References: <20190718134954.496297975@infradead.org> <20190718135205.916241783@infradead.org> <20190719084956.GA6750@andrea> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190719084956.GA6750@andrea> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 19, 2019 at 10:49:56AM +0200, Andrea Parri wrote: > > @@ -1032,6 +1032,8 @@ rwsem_down_read_slowpath(struct rw_semap > > */ > > if (adjustment && !(atomic_long_read(&sem->count) & > > (RWSEM_WRITER_MASK | RWSEM_FLAG_HANDOFF))) { > > + /* Provide lock ACQUIRE */ > > + smp_acquire__after_ctrl_dep(); > > Does this also make the lock RCtso? Or maybe RCtso was already > guaranteed (and I'm failing to see why)? I didn't specifically look for that, but I suspect not, esp given the next patch.