From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH v3 hmm 08/12] mm/hmm: Remove racy protection against double-unregistration Date: Wed, 19 Jun 2019 01:19:48 -0700 Message-ID: <20190619081948.GC24900@infradead.org> References: <20190614004450.20252-1-jgg@ziepe.ca> <20190614004450.20252-9-jgg@ziepe.ca> <20190615141612.GH17724@infradead.org> <20190618131324.GF6961@ziepe.ca> <20190618132722.GA1633@infradead.org> <20190618185757.GP6961@ziepe.ca> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <20190618185757.GP6961-uk2M96/98Pc@public.gmane.org> List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org Sender: "amd-gfx" To: Jason Gunthorpe Cc: Andrea Arcangeli , Philip Yang , Ralph Campbell , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, John Hubbard , Felix.Kuehling-5C7GfCeVMHo@public.gmane.org, dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, Christoph Hellwig , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Jerome Glisse , amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, Ben Skeggs T24gVHVlLCBKdW4gMTgsIDIwMTkgYXQgMDM6NTc6NTdQTSAtMDMwMCwgSmFzb24gR3VudGhvcnBl IHdyb3RlOgo+IFdpdGggdGhlIHByZXZpb3VzIGxvb3NlIGNvdXBsaW5nIG9mIHRoZSBtaXJyb3Ig YW5kIHRoZSByYW5nZSBzb21lIGNvZGUKPiBtaWdodCByYW5jZSB0byB0cnkgdG8gY3JlYXRlIGEg cmFuZ2Ugd2l0aG91dCBhIG1pcnJvciwgd2hpY2ggd2lsbCBub3cKPiByZWxpYWJseSBjcmFzaCB3 aXRoIHRoZSBwb2lzb24uCj4gCj4gSXQgaXNuJ3Qgc28gbXVjaCB0aGUgZG91YmxlIHVucmVnaXN0 ZXIgdGhhdCB3b3JyaWVzIG1lLCBidXQgcmFjaW5nCj4gdW5yZWdpc3RlciB3aXRoIHJhbmdlIGZ1 bmN0aW9ucy4KCk9oIHdlbGwuICBJdCB3YXMganVzdCBhIG5pdHBpY2sgZm9yIHRoZSBoaWdobHkg dW51c3VhbCBjb2RlIHBhdHRlcm5zCmluIHRoZSB0d28gdW5yZWdpc3RlciByb3V0aW5lcywgcHJv YmFibHkgbm90IHdvcnRoIGZpZ2h0aW5nIG92ZXIgZXZlbgppZiBJIHN0aWxsIGRvbid0IHNlZSB0 aGUgcG9pbnQuCl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f CmFtZC1nZnggbWFpbGluZyBsaXN0CmFtZC1nZnhAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHBz Oi8vbGlzdHMuZnJlZWRlc2t0b3Aub3JnL21haWxtYW4vbGlzdGluZm8vYW1kLWdmeA== 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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 1E9E7C31E49 for ; 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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id l2si2447055pgs.315.2019.06.19.01.19.51 for (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 19 Jun 2019 01:19:51 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of batv+77cd4ac56e5e79ab4dbe+5778+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=tf5cAthD; spf=pass (google.com: best guess record for domain of batv+77cd4ac56e5e79ab4dbe+5778+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=BATV+77cd4ac56e5e79ab4dbe+5778+infradead.org+hch@bombadil.srs.infradead.org 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=Oj2mVxSa+2J+fkcSLZJgmIgirExhWFgh1cb5vCMP3vI=; b=tf5cAthDjPtD5dgpkrrmWm6iX hJT+iCl3LI50nk+ly+ZUajqlu/ZYu5I81HuuxxEoOqgz7cy6G/879N+lqH8TGVpEIzKb8gY3RWEH3 spycirx2fT31SjuibyhyqizZP8JiXuZ7DC4RaFSjwiDEGgpm42e6/0HTM69qw1BUen2f8789MSOfC 3BFfTed174q1HfdzIVms/k2iwj1c/fqiYCnF/5TegT2vD/aAyWCTylC372dVxF67j6a4/CwjOm3IO /J6MW7+6GXoWPYd0XJsHHz0VI9rAa4XLWjR2isQ4WJ9LmCy9LcN2FEXjp26JXuspZegFhyO4rNb9S ZStiJlmvw==; Received: from hch by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hdVoq-0000mV-EN; Wed, 19 Jun 2019 08:19:48 +0000 Date: Wed, 19 Jun 2019 01:19:48 -0700 From: Christoph Hellwig To: Jason Gunthorpe Cc: Christoph Hellwig , Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com, linux-rdma@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Ben Skeggs , Philip Yang Subject: Re: [PATCH v3 hmm 08/12] mm/hmm: Remove racy protection against double-unregistration Message-ID: <20190619081948.GC24900@infradead.org> References: <20190614004450.20252-1-jgg@ziepe.ca> <20190614004450.20252-9-jgg@ziepe.ca> <20190615141612.GH17724@infradead.org> <20190618131324.GF6961@ziepe.ca> <20190618132722.GA1633@infradead.org> <20190618185757.GP6961@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190618185757.GP6961@ziepe.ca> User-Agent: Mutt/1.11.4 (2019-03-13) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jun 18, 2019 at 03:57:57PM -0300, Jason Gunthorpe wrote: > With the previous loose coupling of the mirror and the range some code > might rance to try to create a range without a mirror, which will now > reliably crash with the poison. > > It isn't so much the double unregister that worries me, but racing > unregister with range functions. Oh well. It was just a nitpick for the highly unusual code patterns in the two unregister routines, probably not worth fighting over even if I still don't see the point.