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 95C9BC33CB2 for ; Wed, 15 Jan 2020 14:34:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 67A2F214AF for ; Wed, 15 Jan 2020 14:34:02 +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="tjJPtw9y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729037AbgAOOd7 (ORCPT ); Wed, 15 Jan 2020 09:33:59 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:41876 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726248AbgAOOd6 (ORCPT ); Wed, 15 Jan 2020 09:33:58 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=ocli91BL+s6cyrAhg7WkojTpfADiap1nxPT4SxAedzw=; b=tjJPtw9yH/qzdfnHd/0Tg4XM1 N9ZXDuLEoPijn7fFyz59nCDWohkV/2dOvJPpDU2It+cHWikpgvom4e+7YXHwBqQc4oreE0txkzog2 u4bejyWBAGiUhyDSKG7+7Al1NNJsZOFrKx5UGxrj+3+dDvqucqU8+FhJ3USoyzBXXSAisoZmm2cfm afIPFnROkNQz4LDeaWq0KbPlBaRljjAQDwDaX8voRwgRmcEb3rsccJ59uqAxpHC3EVmBAKZMy2DQS 22DWjrnw26k46n22bIWnsoloZtuqV/66JWl9HMpXEAGfQBSyH1z0WePlruqGDLBo5fwTUb4SK+rC4 G0f5/Lh8g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1irjjy-0001bu-Cy; Wed, 15 Jan 2020 14:33:50 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 0596130257C; Wed, 15 Jan 2020 15:32:11 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 599A720B2867B; Wed, 15 Jan 2020 15:33:47 +0100 (CET) Date: Wed, 15 Jan 2020 15:33:47 +0100 From: Peter Zijlstra To: Jason Gunthorpe Cc: Christoph Hellwig , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Waiman Long , Thomas Gleixner , Ingo Molnar , Will Deacon , Andrew Morton , linux-ext4@vger.kernel.org, cluster-devel@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: RFC: hold i_rwsem until aio completes Message-ID: <20200115143347.GL2827@hirez.programming.kicks-ass.net> References: <20200114161225.309792-1-hch@lst.de> <20200114192700.GC22037@ziepe.ca> <20200115065614.GC21219@lst.de> <20200115132428.GA25201@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200115132428.GA25201@ziepe.ca> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed, Jan 15, 2020 at 09:24:28AM -0400, Jason Gunthorpe wrote: > I was interested because you are talking about allowing the read/write side > of a rw sem to be held across a return to user space/etc, which is the > same basic problem. No it is not; allowing the lock to be held across userspace doesn't change the owner. This is a crucial difference, PI depends on there being a distinct owner. That said, allowing the lock to be held across userspace still breaks PI in that it completely wrecks the ability to analyze the critical section.