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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_MUTT autolearn=unavailable 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 075B4C04AAF for ; Tue, 21 May 2019 15:44:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BD23D208C3 for ; Tue, 21 May 2019 15:44:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BD23D208C3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3F3B66B0003; Tue, 21 May 2019 11:44:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3A8696B0006; Tue, 21 May 2019 11:44:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 294A46B000A; Tue, 21 May 2019 11:44:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) by kanga.kvack.org (Postfix) with ESMTP id 0B1956B0003 for ; Tue, 21 May 2019 11:44:27 -0400 (EDT) Received: by mail-qt1-f200.google.com with SMTP id y13so17697300qtc.7 for ; Tue, 21 May 2019 08:44:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:date:from:to :cc:subject:message-id:references:mime-version:content-disposition :content-transfer-encoding:in-reply-to:user-agent; bh=wwgXvngLUewduEoJk6vGYKWssdUC6gdpM8dVj9HDemM=; b=T8xgwQYnlz9a/4vbsoV5E1bYodduy57J3bC8oo7m9z0XgyLo6Mhkxkhf3Fo8SR7UHU QSeAXZ+9HMDge4T/H4NZQgH5cXWjuTK6GcMYU848yDSpz8q5Vli6qjjHrszvHmkPToKr fd1IKF11sEhVGWx2qg11HjqQxlX5zDCGxizzt0tb1Sj2vswQgjuHm3aEVfSh+lZM8zok JUngOmCD//BHRxgTp48jtbx4v5LE4boCT961Yu8yFSooS/S3NbLWv3t8dv3gGtn8xrjs RuXmcXzO3LrDaZOz9DP50V6EnJozkknQ50AV9EkN1+U8tOn3xlSzLA7Ag7WnpXdfW0sl jOHA== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jglisse@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com X-Gm-Message-State: APjAAAW1TVyHczZTG5+MkW9Z/iBsCehsoqtuo6+RqAx8LZ6R1uO/toCV JkWDAmBbHUr8f7lpsXLYR6bkH6MFNnYthCcyazKEeWOymOjWBSM3lhwFLS4TnN7NSYT3f80ul2r DgKTNucMSSjCdBCpKUiut93ogbuHRwNZQ3keMvNc4bN0FUn8/mscu8MAXddB21sfq9Q== X-Received: by 2002:a0c:88d1:: with SMTP id 17mr16189879qvo.116.1558453466819; Tue, 21 May 2019 08:44:26 -0700 (PDT) X-Google-Smtp-Source: APXvYqw/ThDT8PWrWGQxSogdEx2rj8nvezOXXOCkMCVLBq8TwPelMXeH0/GWKEeCGmj1GfbFpAZd X-Received: by 2002:a0c:88d1:: with SMTP id 17mr16189818qvo.116.1558453466161; Tue, 21 May 2019 08:44:26 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1558453466; cv=none; d=google.com; s=arc-20160816; b=JC2pHCiFR1mKs79nPu56SKLR0UPb/DiXMv6fhQdCbpXGjOAq5v5dN94Vom2HMMxJoK gvJUMoMCnMBkstKGNV1cU3GTWcOBg/vAdrEU4DwVDZ12eVHdQb0yj3loZAP28Q8fp6tS 5KGPwzTHmdH6pIz4QYKnsxlQxGtC7GC/8ujxF3tpStu7/f6Op22SMt0NAsAslqiUyGFw 9CDSuMf9D9UZkvkle5OglQlSFfIQv+9C7fUuUZADvwk5q6A30TuhMEkptZvGdf0zkYbZ ulBURbUF7UBDKsd05N6+2sR56PV+Si+O20/gKwThws4bjFAhNRxtQMgEB0AkSXLEsJbE rTlQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-transfer-encoding :content-disposition:mime-version:references:message-id:subject:cc :to:from:date; bh=wwgXvngLUewduEoJk6vGYKWssdUC6gdpM8dVj9HDemM=; b=taqxCAtUBzqEkhvSpDgWDSROdB8XlHpnZmHk6NDZKJp7GHLL2CdIU7h5+WOOk3E0nq 3SseD45R2X160c/BZqKRASjXMGwHNCiJM4YzHIVvIrSLIpbySnDuBkbWzT+Wl4utnOBF jBWzRiHK2G9noaccpHZvw9+lYjU/P5d9A5UpFixg4gqcPL40zn7WTwzU59rU0F/UaIpb 19lkd5vJK4/euE1uVh+iGRyb8bEWwP3hHCXuuFN3AnPx+/8cbTMHSXFcaANnkRkQpAI6 UwpQxY3v+RNIxH/B8tLHRqfAQiejO6icr0HwGRFX58bY/ddH0SWF6+eHnqFBRwQqYd3a 2M1g== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jglisse@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id p5si5907334qke.193.2019.05.21.08.44.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 May 2019 08:44:26 -0700 (PDT) Received-SPF: pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jglisse@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 53D0AC05E760; Tue, 21 May 2019 15:44:15 +0000 (UTC) Received: from redhat.com (unknown [10.20.6.178]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3DA9D17F34; Tue, 21 May 2019 15:44:13 +0000 (UTC) Date: Tue, 21 May 2019 11:44:11 -0400 From: Jerome Glisse To: Daniel Vetter Cc: DRI Development , Intel Graphics Development , LKML , Linux MM , Andrew Morton , Michal Hocko , Christian =?iso-8859-1?Q?K=F6nig?= , David Rientjes , Paolo Bonzini , Daniel Vetter Subject: Re: [PATCH 1/4] mm: Check if mmu notifier callbacks are allowed to fail Message-ID: <20190521154411.GD3836@redhat.com> References: <20190520213945.17046-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190520213945.17046-1-daniel.vetter@ffwll.ch> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Tue, 21 May 2019 15:44:20 +0000 (UTC) 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 Mon, May 20, 2019 at 11:39:42PM +0200, Daniel Vetter wrote: > Just a bit of paranoia, since if we start pushing this deep into > callchains it's hard to spot all places where an mmu notifier > implementation might fail when it's not allowed to. > > Inspired by some confusion we had discussing i915 mmu notifiers and > whether we could use the newly-introduced return value to handle some > corner cases. Until we realized that these are only for when a task > has been killed by the oom reaper. > > An alternative approach would be to split the callback into two > versions, one with the int return value, and the other with void > return value like in older kernels. But that's a lot more churn for > fairly little gain I think. > > Summary from the m-l discussion on why we want something at warning > level: This allows automated tooling in CI to catch bugs without > humans having to look at everything. If we just upgrade the existing > pr_info to a pr_warn, then we'll have false positives. And as-is, no > one will ever spot the problem since it's lost in the massive amounts > of overall dmesg noise. > > v2: Drop the full WARN_ON backtrace in favour of just a pr_warn for > the problematic case (Michal Hocko). > > v3: Rebase on top of Glisse's arg rework. > > v4: More rebase on top of Glisse reworking everything. > > Cc: Andrew Morton > Cc: Michal Hocko > Cc: "Christian König" > Cc: David Rientjes > Cc: Daniel Vetter > Cc: "Jérôme Glisse" > Cc: linux-mm@kvack.org > Cc: Paolo Bonzini > Reviewed-by: Christian König > Signed-off-by: Daniel Vetter Reviewed-by: Jérôme Glisse > --- > mm/mmu_notifier.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c > index ee36068077b6..c05e406a7cd7 100644 > --- a/mm/mmu_notifier.c > +++ b/mm/mmu_notifier.c > @@ -181,6 +181,9 @@ int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range) > pr_info("%pS callback failed with %d in %sblockable context.\n", > mn->ops->invalidate_range_start, _ret, > !mmu_notifier_range_blockable(range) ? "non-" : ""); > + if (!mmu_notifier_range_blockable(range)) > + pr_warn("%pS callback failure not allowed\n", > + mn->ops->invalidate_range_start); > ret = _ret; > } > } > -- > 2.20.1 >