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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 6BA61C43331 for ; Wed, 1 Apr 2020 16:27:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0FE0E20BED for ; Wed, 1 Apr 2020 16:27:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585758423; bh=zR33c3ukV1Gcj2yfkk4F9RTylBrZ8a4WpTR7l2ZGyEY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=FI50IFkOaBX1/VmjzLRZ6w1haNOGtc7511ymLhJveekvrrg+n4+6CQqXBhyuJDUZm 1x9CGbttwRzVs5jw1uBJM3bUVbZhD+zADUDNG01IA+6jSELZl77m+d+S/ag+bdJbCL Estnr1uzwMJi9rlikjHZFZG2TUqzzJ4cp1l6aoL4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387960AbgDAQ1C (ORCPT ); Wed, 1 Apr 2020 12:27:02 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:46430 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387661AbgDAQ1A (ORCPT ); Wed, 1 Apr 2020 12:27:00 -0400 Received: by mail-wr1-f65.google.com with SMTP id j17so731413wru.13 for ; Wed, 01 Apr 2020 09:26:58 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=5o65WF39ZTwNaQXXfGkY0C2ezkDV3cJK8zkl+Yba67k=; b=tUT5zpi1DyEwy9utUcX8lWJ1Gke/dmAaD/Z/92ZxfCOooP06FqRvm8AeOOIITLnlHL 3rZbniG1XjtG7hNUiSxR+w2/Q2Hgi43Awgw8FadmzZ8Oz/A0QUykOWUZ1QU79jfJQgzC vO9STBbeo17RIssqXFaFj1mT3af2JqPDIv9crkuOM0mk09AngXflMS+4W6M2/pRm+VuO p/j8lD4l7hy7sqeZQgbR/hc/hno/Wp09RQb0AxbCuZILpXVa4HrZQVmX7/pWFKcaiLTt gymyOLOTy46ELzcnBImR4u57zUrC2WFFDt3tGmLN7HbRBmvtPN2lhnEdbfnp6DJp/pkI d/yA== X-Gm-Message-State: AGi0PuYRRzuoJerUrhFNavSzLjjWPCQOu5RzkaMg5ajsenEh7P5yHqrD mwO0rnDg95hA1G0suWwRSvc= X-Google-Smtp-Source: APiQypIzVS6Ypqmag+o84P4FAzvoeTwfZ/4rIAQ1v95KbNZdM46U22WRQG7EITfBWMushOM2t8LZ3Q== X-Received: by 2002:a05:6000:108f:: with SMTP id y15mr4809824wrw.423.1585758418302; Wed, 01 Apr 2020 09:26:58 -0700 (PDT) Received: from localhost (ip-37-188-180-223.eurotel.cz. [37.188.180.223]) by smtp.gmail.com with ESMTPSA id a82sm6434836wmh.0.2020.04.01.09.26.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Apr 2020 09:26:57 -0700 (PDT) Date: Wed, 1 Apr 2020 18:26:55 +0200 From: Michal Hocko To: Daniel Jordan , Vlastimil Babka Cc: David Hildenbrand , Shile Zhang , Andrew Morton , Kirill Tkhai , Pavel Tatashin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm: fix tick timer stall during deferred page init Message-ID: <20200401162655.GX22681@dhcp22.suse.cz> References: <20200311123848.118638-1-shile.zhang@linux.alibaba.com> <20200401154217.GQ22681@dhcp22.suse.cz> <20200401160048.GU22681@dhcp22.suse.cz> <20200401160929.jwekhr24tb44odea@ca-dmjordan1.us.oracle.com> <20200401161243.GW22681@dhcp22.suse.cz> <20200401161810.xvqikca2x46yqrlx@ca-dmjordan1.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200401161810.xvqikca2x46yqrlx@ca-dmjordan1.us.oracle.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 01-04-20 12:18:10, Daniel Jordan wrote: > On Wed, Apr 01, 2020 at 06:12:43PM +0200, Michal Hocko wrote: > > On Wed 01-04-20 12:09:29, Daniel Jordan wrote: > > > On Wed, Apr 01, 2020 at 06:00:48PM +0200, Michal Hocko wrote: > > > > On Wed 01-04-20 17:50:22, David Hildenbrand wrote: > > > > > On 01.04.20 17:42, Michal Hocko wrote: > > > > > > This needs a double checking but I strongly believe that the lock can be > > > > > > simply dropped in this path. > > > > > > This is what my fix does, it limits the time the resize lock is held. > > > > Just remove it from the deferred intialization and add a comment that we > > deliberately not taking the lock here because abc > > I think it has to be a little more involved because of the window where > interrupts might allocate during deferred init, as Vlastimil pointed out a few > years ago when the change was made. I do not remember any details but do we have any actual real allocation failure or was this mostly a theoretical concern. Vlastimil? For your context we are talking about 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages") > I'll explain myself in the changelog. OK, I will wait for the patch. -- Michal Hocko SUSE Labs